Bioprocessing strategies for cost-effective simultaneous removal of chromium and malachite green by marine alga Enteromorpha intestinalis

A large number of industries use heavy metal cations to fix dyes in fabrication processes. Malachite green (MG) is used in many factories and in aquaculture production to treat parasites, and it has genotoxic and carcinogenic effects. Chromium is used to fix the dyes and it is a global toxic heavy metal. Face centered central composite design (FCCCD) has been used to determine the most significant factors for enhanced simultaneous removal of MG and chromium ions from aqueous solutions using marine green alga Enteromorpha intestinalis biomass collected from Jeddah beach. The dry biomass of E. intestinalis samples were also examined using SEM and FTIR before and after MG and chromium biosoptions. The predicted results indicated that 4.3 g/L E. intestinalis biomass was simultaneously removed 99.63% of MG and 93.38% of chromium from aqueous solution using a MG concentration of 7.97 mg/L, the chromium concentration of 192.45 mg/L, pH 9.92, the contact time was 38.5 min with an agitation of 200 rpm. FTIR and SEM proved the change in characteristics of algal biomass after treatments. The dry biomass of E. intestinalis has the capacity to remove MG and chromium from aquatic effluents in a feasible and efficient manner.

Low-cost physicochemical treatment for removal of ammonia, phosphate and nitrate contaminants from landfill leachate

Four low-cost materials, oyster shells, pumice stone, sand and zeolite were employed as adsorbents in an adsorption batch assays investigating the removal of ammonia, phosphate and nitrate from an aqueous solution. These compounds were chosen as they represent typical compounds found in landfill leachate (LFL). Assay performance was evaluated by the Langmuir and Freundlich adsorption isotherms. The top two materials, oyster shells and pumice stone, were employed as adsorbents in a fixed-bed column trial examining the effect of bed height and flow rate on the treatment of a synthetic LFL. The trial concluded that the highest rates of adsorption were achieved using bed heights of 20 cm with a flow rate of 5 mL min^-1. After optimization, the system was employed for the treatment of LFL from Powerstown landfill, Carlow, Ireland. Ammonia and nitrate were effectively removed by both adsorption materials resulting in a reduction of influent ammonia and nitrate concentrations to below the national discharge limits set for these compounds of ≤4 mg L^-1 and ≤50 mg L^-1, respectively. In contrast, although similar high removal efficiencies were observed for phosphate, these rates were not maintained during the test period with overall results indicating reduced phosphate adsorption in comparison to the other compounds tested.

Surface water pollution by pharmaceuticals and an alternative of removal by low-cost adsorbents: A review

Micropollutants, also called emerging contaminants, consist of an extensive group of synthetic and natural substances, including pharmaceuticals, personal care products, steroid hormones, and agrochemicals. Currently, the monitoring of residual pharmaceuticals in the environment has been highlighted due to the fact that many of these substances are found in wastewater treatment plants effluents and surface waters, in concentrations ranging from ng L^-1 to μg L^-1. Most of these compounds are discharged into the environment continuously through domestic sewage treatment systems. In the present work, it is presented an overview of water pollution by these pollutants, as well as a review of the recent literature about the use of low-cost adsorbents for the removal of the main pharmaceuticals found in surface water, focusing on municipal and agroindustrial wastes as precursors. It was possible to observe several examples of high adsorption capacities of these compounds with such materials, however other aspects must be considered in order to evaluate the real applicability in water and wastewater treatment, such as competition, recyclability and production cost.

Economic benefits of reducing agricultural N losses to coastal waters for seaside recreation and real estate value in Denmark

We estimate economic benefits for seaside recreation and waterfront property when reducing nitrogen leaching to coastal water bodies. We apply impact pathway and benefit transfer methodology, linking total nitrogen concentration to water clarity (Secchi-depth). Ten catchments are analyzed comparing results for 2010 to a policy scenario that complies with the EU Water Framework Directive. The scenario reduces leaching with 5200 ton N, downstream discharges to estuaries by 35% and provide significant Secchi-depth improvements. Our integrated assessment predicts an annual economic benefit for local residents of €35 million, and co-benefits of up to €57 million. Benefits are catchment-specific and differ for downstream discharges from €1 to €32 per kg N, while for upstream discharge losses they range up to €10 per kg N. When expressed per unit of farmland the policy scenario displays economic benefits spanning €8-176/ha. The span reflects the different physical, biological and human circumstances of each catchment.

Operation costs of the solar photo-catalytic degradation of pharmaceuticals in water: A mini-review

The removal of pharmaceuticals present in wastewater is receiving more and more attention since most of them are refractory to traditional biological treatments. Many advanced oxidation processes have been reported in literature. However, cost estimations are not available for most of them. Recently, more environment friendly processes using solar radiation are gaining importance. The solar photo-Fenton process has been used with different reactor configurations and scales and seems to be the most promising technology for reducing operation costs. In addition, the use of ferrioxalate-aided systems allows the use of pHs close to neutrality, that reduces costs before disposal (not calculated here). The possible use of photovoltaic panels for an energy-free process makes it very interesting for an economic evaluation. Results for the homogeneous solar photo-Fenton process show that when pure compounds are present in water, mineralization is in the range 18-21% with an estimated operation cost of 0.739-0.85 €/m³. An increase in mineralization up to 60-80.6% requires either the use of ferrioxalate (slightly increasing costs to 1.1-1.56 €/m³) or the addition of very high concentration of H₂O₂, that rises costs substantially. The presence of pharmaceuticals in a Waste Water Treatment Plant effluent reduces mineralization (maximum of 20%) also increasing costs. On the other hand, published results confirm that heterogeneous photocatalysis with TiO₂ (both suspended or immobilized) is still far to compete with homogeneous photo-Fenton process in operation costs. The development of new reactor systems and modified photo-catalysts are needed to compete as an efficient applicable technology in the near future.

Comparative risk assessment of oil spill response options for a deepwater oil well blowout: Part II. Relative risk methodology

Subsea dispersant injection (SSDI) was a new oil spill response (OSR) technology deployed during the Deepwater Horizon accident. To integrate SSDI into future OSR decisions, a hypothetical deepwater oil spill to the Gulf of Mexico was simulated and a comparative risk assessment (CRA) tool applied to contrast three response strategies: (1) no intervention; (2) mechanical recovery, in-situ burning, and surface dispersants; and, (3) SSDI in addition to responses in (2). A comparative ecological risk assessment (CRA) was applied to multiple valued ecosystem components (VECs) inhabiting different environmental compartments (ECs) using EC-specific exposure and relative VEC population density and recovery time indices. Results demonstrated the added benefit of SSDI since relative risks to shoreline, surface wildlife and most aquatic life VECs were reduced. Sensitivity of results to different assumptions was also tested to illustrate flexibility of the CRA tool in addressing different stakeholder priorities for mitigating the impacts of a deepwater blowout.

Spatial Characteristics and Driving Factors of Provincial Wastewater Discharge in China

Based on the increasing pressure on the water environment, this study aims to clarify the overall status of wastewater discharge in China, including the spatio-temporal distribution characteristics of wastewater discharge and its driving factors, so as to provide reference for developing “emission reduction” strategies in China and discuss regional sustainable development and resources environment policies. We utilized the Exploratory Spatial Data Analysis (ESDA) method to analyze the characteristics of the spatio-temporal distribution of the total wastewater discharge among 31 provinces in China from 2002 to 2013. Then, we discussed about the driving factors, affected the wastewater discharge through the Logarithmic Mean Divisia Index (LMDI) method and classified those driving factors. Results indicate that: (1) the total wastewater discharge steadily increased, based on the social economic development, with an average growth rate of 5.3% per year; the domestic wastewater discharge is the main source of total wastewater discharge, and the amount of domestic wastewater discharge is larger than the industrial wastewater discharge. There are many spatial differences of wastewater discharge among provinces via the ESDA method. For example, provinces with high wastewater discharge are mainly the developed coastal provinces such as Jiangsu Province and Guangdong Province. Provinces and their surrounding areas with low wastewater discharge are mainly the undeveloped ones in Northwest China; (2) The dominant factors affecting wastewater discharge are the economy and technological advance; The secondary one is the efficiency of resource utilization, which brings about the unstable effect; population plays a less important role in wastewater discharge. The dominant driving factors affecting wastewater discharge among 31 provinces are divided into three types, including two-factor dominant type, three-factor leading type and four-factor antagonistic type. In addition, the proposals aimed at reducing the wastewater discharge are provided on the basis of these three types.

An extended study on historical mercury accumulation in lake sediment of Shanghai: The contribution of socioeconomic driver

Rapid industrialization and urbanization has caused large emission and potential contamination of mercury (Hg) in urban environment. However, little is known about the impact of socioeconomic factor on Hg accumulation in sediment. In the present study, historical record of anthropogenic Hg deposition of Shanghai was reconstructed by using three sediment cores from three park lakes (C1: Luxun Park; C2: Fuxing island Park; C3: Xinjiangwan Park). Meanwhile, the influence of socioeconomic factor to Hg emissions and sedimentary record was calculated based on an extended STIRPAT (stochastic impacts by regression on population, affluence and technology) model. The profiles of Hg levels and fluxes in the three sediment cores showed that Shanghai has recently undergone urbanization. The anthropogenic Hg fluxes exhibited fluctuant increases from ∼1900 to present and accelerated after the establishment of the People's Republic of China in 1949 and the implementation of reform and opening up policy in 1978. The mean flux ratios of Hg in post-2000 were 2.2, 12, and 2.7 in the C1, C2 and C3 cores, respectively. The extended STIRPAT model was constructed based on strong positive relationships between socioeconomic factors and Hg fluxes, revealing that the proportion of coal consumption, the urbanization rate, and the proportion of heavy industry were the three most important driving factors for Hg accumulations in urban sediment of Shanghai.

A robust and cost-effective integrated process for nitrogen and bio-refractory organics removal from landfill leachate via short-cut nitrification, anaerobic ammonium oxidation in tandem with electrochemical oxidation

A cost-effective process, consisting of a denitrifying upflow anaerobic sludge blanket (UASB), an oxygen-limited anoxic/aerobic (A/O) process for short-cut nitrification, and an anaerobic reactor (ANR) for anaerobic ammonia oxidation (anammox), followed by an electrochemical oxidation process with a Ti-based SnO2-Sb2O5 anode, was developed to remove organics and nitrogen in a sewage diluted leachate. The final chemical oxygen demand (COD), ammonia nitrogen (NH4(+)-N) and total nitrogen (TN) of 70, 11.3 and 39 (all in mg/L), respectively, were obtained. TN removal in UASB, A/O and ANR were 24.6%, 49.6% and 16.1%, respectively. According to the water quality and molecular biology analysis, a high degree of anammox besides short-cut nitrification and denitrification occurred in A/O. Counting for 16.1% of TN removal in ANR, at least 43.2-49% of TN was removed via anammox. The anammox bacteria in A/O and ANR, were in respective titers of (2.5-5.9)×10(9) and 2.01×10(10)copy numbers/(gSS).

Is Ongoing Sulfluramid Use in South America a Significant Source of Perfluorooctanesulfonate (PFOS)? Production Inventories, Environmental Fate, and Local Occurrence

Despite international phase-out initiatives, production and use of perfluorooctanesulfonate (PFOS) and related substances continues in some countries. In Brazil, the PFOS-precursor N-ethyl perfluorooctane sulfonamide (EtFOSA) is used in Sulfluramid, a pesticide for controlling leaf-cutting ants. New data on production, environmental fate, and occurrence of Brazilian Sulfluramid are reported herein. From 2003 to 2013, Brazilian Sulfluramid manufacturing increased from 30 to 60 tonnes yr(-1) EtFOSA. During this time <1.3 tonnes yr(-1) were imported, while exports increased from ∼0.3 to 2 tonnes yr(-1). From 2004 to 2015, most EtFOSA was exported to Argentina (7.2 tonnes), Colombia (2.07 tonnes), Costa Rica (1.13 tonnes), Equador (2.16 tonnes), and Venezuela (2.4 tonnes). Within Brazil, sales occurred primarily in the states of Minas Gerais, São Paulo, Mato Grosso do Sul, Espírito Santo, and Bahia. Model simulations predict EtFOSA will partition to soils, while transformation products perfluorooctane sulfonamide (FOSA) and PFOS are sufficiently mobile to leach into surface waters. In support of these predictions, up to 3400 pg L(-1) of FOSA and up to 1100 pg L(-1) of PFOS were measured in Brazilian surface water, while EtFOSA was not detected. The high FOSA/PFOS ratio observed here (up to 14:1) is unprecedented in the scientific literature to our knowledge. Depending on the extent of conversion of EtFOSA, cumulative Brazilian Sulfluramid production and import from 2004 to 2015 may contribute between 167 and 487 tonnes of PFOS/FOSA to the environment. These levels are clearly nontrivial and of concern since production is continuing unabated.

Treatment of urban river contaminated sediment with ex situ advanced oxidation processes: technical feasibility, environmental discharges and cost-performance analysis

The technical feasibility, environmental discharges and cost-performance of urban river contaminated sediment treatment with ex situ advanced oxidation processes were evaluated for the purpose of achieving an ideal treatment goal (for marine disposal) and a cost-performance treatment goal (for beneficially reusing as a filling material). Sediment samples were collected from a river located in southern China. To achieve the ideal treatment goal, sequential treatments (Fenton's reaction+activated persulphate oxidation) were carried out. One-step Fenton's reaction was applied to achieve the cost-performance treatment goal. The resulting effluent was treated and discharged, and sludge generated in wastewater treatment was characterized. The resources input throughout the treatment processes were recorded for cost estimation. After the treatment designed for achieving the ideal treatment goal, most pollutants fulfilled the treatment goal except Pb, Cd, Hg and Ag, probably because these four metals were present mainly in stable fractions of the sediment. The cost-performance treatment goal was achieved in view of low pollutant contents in the toxicity characteristic leaching procedure leachate of treated sediment. The cost for achieving the cost-performance treatment goal is much less than that for achieving the ideal treatment goal. The major cost difference is attributed to chemical cost. Stringent sediment treatment goals based on existing standards would lead to massive chemical use, complex treatment and hence huge cost. A simpler treatment with fewer chemicals is adequate for sediment beneficially reused as a filling material, and is economically more advantageous than handling sediment for marine disposal.

A new algorithm for design, operation and cost assessment of struvite (MgNH4PO4) precipitation processes

Deliberate struvite (MgNH4PO4) precipitation from wastewater streams has been the topic of extensive research in the last two decades and is expected to gather worldwide momentum in the near future as a P-reuse technique. A wide range of operational alternatives has been reported for struvite precipitation, including the application of various Mg(II) sources, two pH elevation techniques and several Mg:P ratios and pH values. The choice of each operational parameter within the struvite precipitation process affects process efficiency, the overall cost and also the choice of other operational parameters. Thus, a comprehensive simulation program that takes all these parameters into account is essential for process design. This paper introduces a systematic decision-supporting tool which accepts a wide range of possible operational parameters, including unconventional Mg(II) sources (i.e. seawater and seawater nanofiltration brines). The study is supplied with a free-of-charge computerized tool (http://tx.technion.ac.il/~agrengn/agr/Struvite_Program.zip) which links two computer platforms (Python and PHREEQC) for executing thermodynamic calculations according to predefined kinetic considerations. The model can be (inter alia) used for optimizing the struvite-fluidized bed reactor process operation with respect to P removal efficiency, struvite purity and economic feasibility of the chosen alternative. The paper describes the algorithm and its underlying assumptions, and shows results (i.e. effluent water quality, cost breakdown and P removal efficiency) of several case studies consisting of typical wastewaters treated at various operational conditions.

Economic total maximum daily load for watershed-based pollutant trading

Water quality trading (WQT) is supported by the US Environmental Protection Agency (USEPA) under the framework of its total maximum daily load (TMDL) program. An innovative approach is presented in this paper that proposes post-TMDL trade by calculating pollutant rights for each pollutant source within a watershed. Several water quality trading programs are currently operating in the USA with an objective to achieve overall pollutant reduction impacts that are equivalent or better than TMDL scenarios. These programs use trading ratios for establishing water quality equivalence among pollutant reductions. The inbuilt uncertainty in modeling the effects of pollutants in a watershed from both the point and nonpoint sources on receiving waterbodies makes WQT very difficult. A higher trading ratio carries with it increased mitigation costs, but cannot ensure the attainment of the required water quality with certainty. The selection of an applicable trading ratio, therefore, is not a simple process. The proposed approach uses an Economic TMDL optimization model that determines an economic pollutant reduction scenario that can be compared with actual TMDL allocations to calculate selling/purchasing rights for each contributing source. The methodology is presented using the established TMDLs for the bacteria (fecal coliform) impaired Muddy Creek subwatershed WAR1 in Rockingham County, Virginia, USA. Case study results show that an environmentally and economically superior trading scenario can be realized by using Economic TMDL model or any similar model that considers the cost of TMDL allocations.

Costs and effectiveness of on-farm measures to reduce aquatic risks from pesticides in the Netherlands

BACKGROUND

The European Union requires growers to implement the principles of integrated pest management (IPM) by 2014. This paper provides a quantitative overview of the costs and effectiveness of voluntary IPM measures in 15 crops in the Netherlands. The authors will focus on aquatic risks and define effectiveness as the potential to reduce the risks posed to aquatic organisms. They further identify which of these measures have actually been adopted by growers and why certain measures have not been adopted.

RESULTS

Of the 105 measures evaluated, the most effective measures with respect to risk reduction were emission reduction and replacement of high-risk pesticides (each up to 80% reduction). IPM measures directed towards lowering pesticide use generally showed a smaller risk-reducing potential. However, 40% of these measures reduced the overall cost of pest management. About 60% of all 105 measures were voluntarily implemented by growers. The most commonly adopted measures were pest prevention, low-dose spraying and spray drift reduction. Cost appeared to be an important incentive for adoption; however, other factors such as risk perception, education and practicability were equally important.

CONCLUSIONS

Voluntary IPM measures have significantly contributed to reducing aquatic risks (15-50% risk reduction, depending on crop type). Further risk reduction could be achieved if more growers were to adopt the most effective measures, such as spray drift reduction and replacement of high-risk pesticides. However, IPM has hardly reduced the number of pesticide applications, and therefore the dependence on chemical crop protection continues to be high.

Household's willingness to pay for arsenic safe drinking water in Bangladesh

This study examines willingness to pay (WTP) in Bangladesh for arsenic (As) safe drinking water across different As-risk zones, applying a double bound discrete choice value elicitation approach. The study aims to provide a robust estimate of the benefits of As safe drinking water supply, which is compared to the results from a similar study published almost 10 years ago using a single bound estimation procedure. Tests show that the double bound valuation design does not suffer from anchoring or incentive incompatibility effects. Health risk awareness levels are high and households are willing to pay on average about 5 percent of their disposable average annual household income for As safe drinking water. Important factors influencing WTP include the bid amount to construct communal deep tubewell for As safe water supply, the risk zone where respondents live, household income, water consumption, awareness of water source contamination, whether household members are affected by As contamination, and whether they already take mitigation measures.

Organic and inorganic contaminants removal from water with biochar, a renewable, low cost and sustainable adsorbent--a critical review

Biochar is used for soil conditioning, remediation, carbon sequestration and water remediation. Biochar application to water and wastewater has never been reviewed previously. This review focuses on recent applications of biochars, produced from biomass pyrolysis (slow and fast), in water and wastewater treatment. Slow and fast pyrolysis biochar production is briefly discussed. The literature on sorption of organic and inorganic contaminants by biochars is surveyed and reviewed. Adsorption capacities for organic and inorganic contaminants by different biochars under different operating conditions are summarized and, where possible, compared. Mechanisms responsible for contaminant remediation are briefly discussed. Finally, a few recommendations for further research have been made in the area of biochar development for application to water filtration.

Nutrient removal from agricultural drainage water using algal turf scrubbers and solar power

The objectives of this study were to determine nutrient removal rates and costs using solar-powered algal turf scrubber (ATS) raceways and water from an agricultural drainage ditch. Algal productivity using daytime-only flow was 3-lower compared to productivity using continuous flow. Results from this and other studies suggest a non-linear relationship between flow rate and nitrogen removal rates. Nitrogen (N) and phosphorus (P) removal rates averaged 125 mg N, 25 mg P m(-2) d(-1) at the highest flow rates. Nutrient removal rates were equivalent to 310 kg N and 33 kg P ha(-1) over a 7 month season. Projected nutrient removal costs ($90-$110 kg(-1) N or $830-$1050 kg(-1) P) are >10-fold higher than previous estimates for ATS units used to treat manure effluents.

Determining the effect of environmental accidents on responses to a Gulf of Mexico recreational for-hire fishing industry survey

A survey designed to collect economic, attitudinal and policy data from the recreational for-hire (RFH) fishing industry in the U.S. Gulf of Mexico was conducted before and during the largest marine oil spill in U.S. history (the April 2010 Deepwater Horizon blowout). Respondents were grouped into two time periods based on when the survey was completed, where the break in groups was determined through the examination of the Pew Research Center's media coverage index and the per cent of fishing area closures due to the oil spill. A logistic regression was used to test variables that might predict the time period of a response. Results indicated that recall bias was not present in the financial variables examined, but that firm operating and demographic characteristics (i.e. vessel size, annual number of trips, number of vessels operating in the firm, tenure and household income) were significant in explaining the time period in which surveys were completed.

U.S. Department of Defense and White House Working Together to Avoid Cleanup and Liability for Perchlorate Pollution

The toxic anti-thyroidic chemical perchlorate, used in rocket fuel, has leached from military dumpsites into public drinking water sources, contaminating the water at dangerous levels in many states. The Department of Defense and its contractors such as Lockheed Martin are using obfuscation to wage a campaign to slow or block Environmental Protection Agency regulatory measures that might cost them billions of dollars in cleanup and liability. The influence of the DOD over the EPA is cause for extreme concern.

Composite hollow fiber nanofiltration membranes for recovery of glyphosate from saline wastewater

A high performance versatile composite hollow fiber nanofiltration (NF) membrane is reported for the separation of glyphosate from saline waste streams. Preparation of SPEEK based on an amorphous poly (ether ether ketone, PEEK) was investigated. The membrane was prepared by coating sulfonated polyether ether ketone (SPEEK) onto a polyethersulfone (PES) ultrafiltration (UF) hollow fiber membrane. The composite membrane was characterized by water permeability, scanning electron microscopy, and rejection toward sodium sulfate (Na₂SO₄), sodium chloride (NaCl), and calcium chloride (CaCl₂). About 90% rejection toward sulfate anions and only 10% rejection for calcium cations were obtained. A water permeability around 10-13 LMHBar and 90% rejection for polyethylene glycol (PEG) with a molecular weight of 4000-6000 Da were observed. In the separation of glyphosate from saline wastewater, the membrane rejected less than 20% of NaCl and higher than 90% of glyphosate at an operating pressure of 5 bars and pH = 11.0. An economic analysis indicated that the cost for recovery of glyphosate was comparably low to the value gained by an increase in the productivity. The results may lead to a new promising low energy solution for the environmental problem faced by the herbicide industry.

Economic and toxicological aspects of copper industry in Katanga, DR Congo

The Katanga province is well known for its copper and cobalt reserves. During the early 2000s a boom of mining projects in Katanga brought again hope for better future to Congolese people. The paper aims to evaluate the impact of recent production recovery on economy and environment. We collected primary and secondary sources on copper industry for economic analysis. We use results of laboratory analysis conducted at the Congolese Office of Control by provincial division of environment for toxicological analysis. The comparison of heavy metal concentration to standards shows that mining industry is the main source of environmental pollution in Katanga. Copper industry generates income for economic growth of the region.

A review of the cost-effectiveness and suitability of mitigation strategies to prevent phosphorus loss from dairy farms in New Zealand and Australia

The loss of phosphorus (P) from land to water is detrimental to surface water quality in many parts of New Zealand and Australia. Farming, especially pasture-based dairying, can be a source of P loss, but preventing it requires a range of fully costed strategies because little or no subsidies are available and the effectiveness of mitigation strategies varies with different farm management systems, topography, stream density, and climate. This paper reviews the cost-effectiveness of mitigation strategies for New Zealand and Australian dairy farms, grouping strategies into (i) management (e.g., decreasing soil test P, fencing streams off from stock, or applying low-water-soluble P fertilizers), (ii) amendments (e.g., alum or red mud [Bauxite residue]), and (iii) edge-of-field mitigations (e.g., natural or constructed wetlands). In general, on-farm management strategies were the most cost-effective way of mitigating P exports (cost range, $0 to $200 per kg P conserved). Amendments, added to tile drains or directly to surface soil, were often constrained by supply or were labor intensive. Of the amendments examined, red mud was cost effective where cost was offset by improved soil physical properties. Edge-of-field strategies, which remove P from runoff (i.e., wetlands) or prevent runoff (i.e., irrigation runoff recycling systems), were generally the least cost effective, but their benefits in terms of improved overall resource efficiency, especially in times of drought, or their effect on other contaminants like N need to be considered. By presenting a wide range of fully costed strategies, and understanding their mechanisms, a farmer or farm advisor is able to choose those that suit their farm and maintain profitability. Further work should examine the potential for targeting strategies to areas that lose the most P in time and space to maximize the cost-effectiveness of mitigation strategies, quantify the benefits of multiple strategies, and identify changes to land use that optimize overall dairy production, but minimize catchment scale, as versus farm scale, nutrient exports.

Municipal wastewater treatment by biofiltration: comparisons of various treatment layouts. Part 2: assessment of the operating costs in optimal conditions

This work aims to compare the operation costs (energy, reagents, waste management) for the three layouts usually used in wastewater treatment plants incorporating biofilters, using technical and economical data acquired during 10 years of operation of a Parisian plant (Seine Centre, 240,000 m(3) d(-1) -800,000 equivalent inhabitants). The final objective is to establish general economical data and tendencies that can be translated from our study to any biofiltration plant. Our results evidenced the savings achieved through the treatment process combining upstream and downstream denitrification. To use this layout reduced the operating costs by some 10% as compared with conventional processing only comprising downstream denitrification. Operating costs were respectively estimated at 37 and 34 €/1,000 m(3) for downstream denitrification and combining upstream and downstream denitrification layouts.

Chemical dosing for sulfide control in Australia: An industry survey

Controlling sulfide (H(2)S) production and emission in sewer systems is critical due to the corrosion and malodour problems that sulfide causes. Chemical dosing is one of the most commonly used measures to mitigate these problems. Many chemicals have been reported to be effective for sulfide control, but the extent of success varies between chemicals and is also dependent on how they are applied. This industry survey aims to summarise the current practice in Australia with the view to assist the water industry to further improve their practices and to identify new research questions. Results showed that dosing is mainly undertaken in pressure mains. Magnesium hydroxide, sodium hydroxide and nitrate are the most commonly used chemicals for sewers with low flows. In comparison, iron salts are preferentially used for sulfide control in large systems. The use of oxygen injection has declined dramatically in the past few years. Chemical dosing is mainly conducted at wet wells and pumping stations, except for oxygen, which is injected into the pipe. The dosing rates are normally linked to the control mechanisms of the chemicals and the dosing locations, with constant or profiled dosing rates usually applied. Finally, key opportunities for improvement are the use of mathematical models for the selection of chemicals and dosing locations, on-line dynamic control of the dosing rates and the development of more cost-effective chemicals for sulfide control.

Reducing surface water pollution through the assessment of the cost-effectiveness of BMPs at different spatial scales

Two kinds of agricultural Best Management Practices (BMPs) were examined with respect to cost-effectiveness (CE) in reducing sediment, nitrates-nitrogen (NO(3)-N) and total phosphorus (TP) losses to surface waters of the Arachtos catchment in Western Greece. The establishment of filter strips at the edge of fields and a non-structural measure, namely fertilization reduction in alfalfa, combined with contour farming and zero-tillage in corn and reduction of animal numbers in pastureland, were evaluated. The Soil and Water Assessment Tool (SWAT) model was used as the non-point-source (NPS) estimator, while a simple economic component was developed estimating BMP implementation cost as the mean annual expenses needed to undertake and operate the practice for a 5-year period. After each BMP implementation, the ratio of their CE in reducing pollution was calculated for each Hydrologic Response Unit (HRU) separately, for each agricultural land use type entirely and for the whole catchment. The results at the HRU scale are presented comprehensively on a map, demonstrating the spatial differentiation of CE ratios across the catchment that enhances the identification of locations where each BMP is most advisable for implementation. Based on the analysis, a catchment management solution of affordable total cost would include the expensive measure of filter strips in corn and only in a small number of pastureland fields, in combination with the profitable measure of reducing fertilization to alfalfa fields. When examined for its impact on river loads at the outlet, the latter measure led to a 20 tn or 8% annual decrease of TP from the baseline with savings of 15€/kg of pollutant reduction. Filter strips in corn fields reduced annual sediments by 66 Ktn or 5%, NO(3)-N by 71 tn or 9.5% and TP by 27 tn or 10%, with an additional cost of 3.1 €/tn, 3.3 €/kg and 8.1 €/kg of each pollutant respectively. The study concludes that considerable reductions of several pollutant types at the same time can be achieved, even at low total cost, by combining targeted BMP implementation strategies only in small parts of the catchment, also enabling policy makers to take local socio-economic constraints into consideration. The methodology and the results presented aim to facilitate decision making for a cost-effective management of diffuse pollution by enabling modelers and researchers to make rapid and reliable BMP cost estimations and thus being able to calculate their CE at the local level in order to identify the most suitable areas for their implementation.

Economic feasibility study for phosphorus recovery processes

Phosphorus recovery from wastewater has become a necessity for sustainable development because phosphorus is a non-renewable essential resource, and its discharge into the environment causes serious negative impacts. There are no economic incentives for the implementation of phosphorus recovery technologies because the selling price of rock phosphate is lower than phosphorus recovered from sewage. The methodologies used to determine the feasibility of such projects are usually focused on internal costs without considering environmental externalities. This article shows a methodology to assess the economic feasibility of wastewater phosphorus recovery projects that takes into account internal and external impacts. The shadow price of phosphorus is estimated using the directional distance function to measure the environmental benefits obtained by preventing the discharge of phosphorus into the environment. The economic feasibility analysis taking into account the environmental benefits shows that the phosphorus recovery is viable not only from sustainable development but also from an economic point of view.

Risk acceptance criterion for tanker oil spill risk reduction measures

This paper is aimed at investigating whether there is ample support for the view that the acceptance criterion for evaluating measures for prevention of oil spills from tankers should be based on cost-effectiveness considerations. One such criterion can be reflected by the Cost of Averting a Tonne of oil Spilt (CATS) whereas its target value is updated by elaborating the inherent uncertainties of oil spill costs and establishing a value for the criterion's assurance factor. To this end, a value of $80,000/t is proposed as a sensible CATS criterion and the proposed value for the assurance factor F=1.5 is supported by the retrieved Protection and Indemnity (P&I) Clubs' Annual Reports. It is envisaged that this criterion would allow the conversion of direct and indirect costs into a non-market value for the optimal allocation of resources between the various parties investing in shipping. A review of previous cost estimation models on oil spills is presented and a probability distribution (log-normal) is fitted on the available oil spill cost data, where it should be made abundantly clear that the mean value of the distribution is used for deriving the updated CATS criterion value. However, the difference between the initial and the updated CATS criterion in the percentiles of the distribution is small. It is found through the current analysis that results are partly lower than the predicted values from the published estimation models. The costs are also found to depend on the type of accident, which is in agreement with the results of previous studies. Other proposals on acceptance criteria are reviewed and it is asserted that the CATS criterion can be considered as the best candidate. Evidence is provided that the CATS approach is practical and meaningful by including examples of successful applications in actual risk assessments. Finally, it is suggested that the criterion may be refined subject to more readily available cost data and experience gained from future decisions.

Economic evaluation of alternative wastewater treatment plant options for pulp and paper industry

Excessive water consumption in pulp and paper industry results in high amount of wastewater. Pollutant characteristics of the wastewater vary depending on the processes used in production and the quality of paper produced. However, in general, high organic material and suspended solid contents are considered as major pollutants of pulp and paper industry effluents. The major pollutant characteristics of pulp and paper industry effluents in Turkey were surveyed and means of major pollutant concentrations, which were grouped in three different pollution grades (low, moderate and high strength effluents), and flow rates within 3000 to 10,000m(3)/day range with 1000m(3)/day steps were used as design parameters. Ninety-six treatment plants were designed using twelve flow schemes which were combinations of physical treatment, chemical treatment, aerobic and anaerobic biological processes. Detailed comparative cost analysis which includes investment, operation, maintenance and rehabilitation costs was prepared to determine optimum treatment processes for each pollution grade. The most economic and technically optimal treatment processes were found as extended aeration activated sludge process for low strength effluents, extended aeration activated sludge process or UASB followed by an aeration basin for medium strength effluents, and UASB followed by an aeration basin or UASB followed by the conventional activated sludge process for high strength effluents.

Estimation of incidence and social cost of colon cancer due to nitrate in drinking water in the EU: a tentative cost-benefit assessment

BACKGROUND

Presently, health costs associated with nitrate in drinking water are uncertain and not quantified. This limits proper evaluation of current policies and measures for solving or preventing nitrate pollution of drinking water resources. The cost for society associated with nitrate is also relevant for integrated assessment of EU nitrogen policies taking a perspective of welfare optimization. The overarching question is at which nitrogen mitigation level the social cost of measures, including their consequence for availability of food and energy, matches the social benefit of these measures for human health and biodiversity.

METHODS

Epidemiological studies suggest colon cancer to be possibly associated with nitrate in drinking water. In this study risk increase for colon cancer is based on a case-control study for Iowa, which is extrapolated to assess the social cost for 11 EU member states by using data on cancer incidence, nitrogen leaching and drinking water supply in the EU. Health costs are provisionally compared with nitrate mitigation costs and social benefits of fertilizer use.

RESULTS

For above median meat consumption the risk of colon cancer doubles when exposed to drinking water exceeding 25 mg/L of nitrate (NO3) for more than ten years. We estimate the associated increase of incidence of colon cancer from nitrate contamination of groundwater based drinking water in EU11 at 3%. This corresponds to a population-averaged health loss of 2.9 euro per capita or 0.7 euro per kg of nitrate-N leaching from fertilizer.

CONCLUSIONS

Our cost estimates indicate that current measures to prevent exceedance of 50 mg/L NO3 are probably beneficial for society and that a stricter nitrate limit and additional measures may be justified. The present assessment of social cost is uncertain because it considers only one type of cancer, it is based on one epidemiological study in Iowa, and involves various assumptions regarding exposure. Our results highlight the need for improved epidemiological studies.

Acidification remediation alternatives: exploring the temporal dimension with cost benefit analysis

Acidification of soils and surface waters caused by acid deposition is still a major problem in southern Scandinavia, despite clear signs of recovery. Besides emission control, liming of lakes, streams, and wetlands is currently used to ameliorate acidification in Sweden. An alternative strategy is forest soil liming to restore the acidified upland soils from which much acidified runoff originates. This cost-benefit analysis compared these liming strategies with a special emphasis on the time perspective for expected benefits. Benefits transfer was used to estimate use values for sport ffishing and nonuse values in terms of existence values. The results show that large-scale forest soil liming is not socioeconomically profitable, while lake liming is, if it is done efficiently-in other words, if only acidified surface waters are treated. The beguiling logic of "solving" an environmental problem at its source (soils), rather than continuing to treat the symptoms (surface waters), is thus misleading.

Considerations on the design and financial feasibility of full-scale membrane bioreactors for municipal applications

Based on the practical experience in design and operation of three full-scale membrane bioreactors (MBR) for municipal wastewater treatment that were commissioned since 1999, an overview on the different design concepts that were applied to the three MBR plants is given. The investment costs and the energy consumption of the MBRs and conventional activated sludge (CAS) plants (with and without tertiary treatment) in the Erft river region are compared. It is found that the specific investment costs of the MBR plants are lower than those of comparable CAS with tertiary treatment. A comparison of the specific energy demand of MBRs and conventional WWTPs is given. The structure of the MBRs actual operational costs is analysed. It can be seen that energy consumption is only responsible for one quarter to one third of all operational expenses. Based on a rough design and empirical cost data, a cost comparison of a full-scale MBR and a CAS is carried out. In this example the CAS employs a sand filtration and a disinfection in order to achieve comparable effluent quality. The influence of membrane lifetime on life cycle cost is assessed.

Operating costs for reducing total emission loads of key pollutants in municipal wastewater treatment plants in China

Total emission load reduction of COD, NH(4)-N, TN, and TP is the key measure in controlling water pollution and eutrophication. Municipal wastewater treatment plants (MWWTPs) are major contributors in lowering energy consumption and reducing pollutant discharge. The flow-based operating costs have not been directly established to relate to costs of pollutant reduction based on an investigation of 11 MWWTPs in China. However, energy consumption to eliminate one kilogram of COD or NH(4)-N was observed to decrease when the total reduced pollutants is increased. Additional energy consumption required to remove nitrogen and phosphorus is allotted for mixers and internal return pumps. Major factors for operating costs include influent and effluent concentration, design capacity, and flow loading rate. Therefore, an operating cost model for the total emission load reduction of COD, NH(4)-N, TN, and TP was developed based on energy consumption and the above mentioned major factors. Using this model to calculate the operating costs for MWWTPs would facilitate more reduction of key pollutants than the flow-based method.

Removal of suspended solids and turbidity from marble processing wastewaters by electrocoagulation: comparison of electrode materials and electrode connection systems

In this study, removal of suspended solids (SS) and turbidity from marble processing wastewaters by electrocoagulation (EC) process were investigated by using aluminium (Al) and iron (Fe) electrodes which were run in serial and parallel connection systems. To remove these pollutants from the marble processing wastewater, an EC reactor including monopolar electrodes (Al/Fe) in parallel and serial connection system, was utilized. Optimization of differential operation parameters such as pH, current density, and electrolysis time on SS and turbidity removal were determined in this way. EC process with monopolar Al electrodes in parallel and serial connections carried out at the optimum conditions where the pH value was 9, current density was approximately 15 A/m(2), and electrolysis time was 2 min resulted in 100% SS removal. Removal efficiencies of EC process for SS with monopolar Fe electrodes in parallel and serial connection were found to be 99.86% and 99.94%, respectively. Optimum parameters for monopolar Fe electrodes in both of the connection types were found to be for pH value as 8, for electrolysis time as 2 min. The optimum current density value for Fe electrodes used in serial and parallel connections was also obtained at 10 and 20 A/m(2), respectively. Based on the results obtained, it was found that EC process running with each type of the electrodes and the connections was highly effective for the removal of SS and turbidity from marble processing wastewaters, and that operating costs with monopolar Al electrodes in parallel connection were the cheapest than that of the serial connection and all the configurations for Fe electrode.

Reclamation of the wastewater from an industrial park using hollow-fibre and spiral-wound membranes: 50 m3 d(-1) pilot testing and cost evaluation

The feasibility of reclaiming effluent from industrial park wastewater treatment plants through a membrane process was evaluated in three phases. In phase 1 we selected nine wastewater treatment plants (WWTPs), each with a design capacity exceeding 10,000 m3 d(-1), and analyzed the corresponding effluent composition. 'Potential recycling percentage', R, ranged from 50% to 80% for the industrial park WWTPs, indicating a high feasibility for the reuse of effluent. In phase 2, a 50 m3 d(-1) pilot plant was installed in one of the selected WWTPs and underwent testing for one year. The quality of the reclaimed water was suitable for general-purpose industrial use. In the two ultrafiltration (UF) modules tested, the hydrophilic polyethersulfone hollow-fibre module was more tolerant to variable properties, and had higher recycling percentages than those of backwashable hydrophobic polyvinylidene difluoride spiral-wound module. Using the spiral-wound UF module helped reduce the cost for producing 1 m3 of reclaimed water (US$0.80) compared with a hollow-fibre module (US$0.88). In phase 3, we evaluated the negative effects of refluxing the reverse osmosis retentate, containing high total dissolved solids and non-biodegradable organics, with the biological treatment unit of the upstream WWTP. Biological compactibility tests showed that the refluxed retentate ratio should be reduced to maintain the conductivity of mixed liquor in the aeration tank at less than 110% of the original value.

Rapid removal of cobalt ion from aqueous solutions by almond green hull

Almond green hull, an agriculture solid waste, was chemically treated and used for the adsorption of Co (II) from aqueous solutions. The efficiency of this new adsorbent was studied using batch adsorption technique under different experimental conditions such as sorbent amount, initial metal-ion concentration, contact time, adsorbent particle size, and chemical treatment. Optimum dose of sorbent for maximum metal-ion adsorption were 0.25 g for 51.5 mg l(-1) and 0.4 g for 110 mg l(-1) solutions, respectively. High removal efficiencies of Co (II) were occurred in the first 1 min of sorbent contact time. The adsorption of Co (II) on almond green hull was also observed to follow the pseudo second-order kinetics. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models. The Langmuir adsorption model fits the experimental data reasonably well compared to the Freundlich model. The maximum adsorption capacity of this new sorbent was found to be 45.5 mg g(-1). The present study revealed that such a low cost material could be used as an efficient sorbent for the removal of cobalt from wastewater streams.

Cost-effective biostimulation strategy for wastewater decolorization using immobilized-cell systems

This study tended to evaluate threshold operation criteria of biostimulation for optimal biodecolorization in immobilized-cell systems (ICSs) using Porites corals as packing matrices. Indigenous Aeromonas hydrophila with high efficiency for decolorization isolated from Northeast Taiwan was used for study. As maximal treatment performance of ICS could only be achieved with maximal absorbed biomass with highest color removal capability. Maintaining optimal attached cells for cost-effective color removal efficiency inevitably required essential nutrients provided from rich media for biostimulation. With consideration of efficient cell attachment and maximal dye biodecolorization, our proposed method of "graphical reconstruction" quantitatively revealed the most economically-feasible strategy of medium stimulation for color removal. Our findings pointed out the maximal allowable inlet concentration and treatment capacity using our prediction of constant-slope isoclines of ICSs at cultures fed with different concentrations of nutrient sources. The method of isoclines upon transient dynamics of ICSs also provided a technically viable assessment for on-site professionals to quantitatively determine maximal biotreatment thresholds in biostimulation.

A game theoretic approach for trading discharge permits in rivers

In this paper, a new Cooperative Trading Discharge Permit (CTDP) methodology is designed for estimating equitable and efficient treatment cost allocation among dischargers in a river system considering their conflicting interests. The methodology consists of two main steps: (1) initial treatment cost allocation and (2) equitable treatment cost reallocation. In the first step, a Pareto front among objectives is developed using a powerful and recently developed multi-objective genetic algorithm known as Nondominated Sorting Genetic Algorithm-II (NSGA-II). The objectives of the optimization model are considered to be the average treatment level of dischargers and a fuzzy risk of violating the water quality standards. The fuzzy risk is evaluated using the Monte Carlo analysis. The best non-dominated solution on the Pareto front, which provides the initial cost allocation to dischargers, is selected using the Young Bargaining Theory (YBT). In the second step, some cooperative game theoretic approaches are utilized to investigate how the maximum saving cost of participating dischargers in a coalition can be fairly allocated to them. The final treatment cost allocation provides the optimal trading discharge permit policies. The practical utility of the proposed methodology for river water quality management is illustrated through a realistic case study of the Zarjub river in the northern part of Iran.

Phosphorus recovery from wastewater: needs, technologies and costs

Phosphorus is an essential, yet limited resource, which cannot be replaced by any other element. This is why there are increasing efforts to recycle phosphorus contained in wastewater. It involves the recovery of phosphorus and, normally, the separation of phosphates from harmful substances. Phosphorus can be recovered from wastewater, sewage sludge, as well as from the ash of incinerated sewage sludge, and can be combined with phosphorus removal in most cases. The phosphorus recovery rate from the liquid phase can reach 40 to 50% at the most, while recovery rates from sewage sludge and sewage sludge ash can reach up to 90%. There are various methods which can be applied for phosphorus recovery. Up to now, there is limited experience in industrial-scale implementation. The costs for recovered phosphate exceed the costs for phosphate from rock phosphate by several times. For German conditions, the specific additional costs of wastewater treatment by integrating phosphorus recovery can be estimated at euro2-6 per capita and year.

Implementing the water framework directive: contract design and the cost of measures to reduce nitrogen pollution from agriculture

The performance of different policy design strategies is a key issue in evaluating programmes for water quality improvement under the Water Framework Directive (60/2000). This issue is emphasised by information asymmetries between regulator and agents. Using an economic model under asymmetric information, the aim of this paper is to compare the cost-effectiveness of selected methods of designing payments to farmers in order to reduce nitrogen pollution in agriculture. A principal-agent model is used, based on profit functions generated through farm-level linear programming. This allows a comparison of flat rate payments and a menu of contracts developed through mechanism design. The model is tested in an area of Emilia Romagna (Italy) in two policy contexts: Agenda 2000 and the 2003 Common Agricultural Policy (CAP) reform. The results show that different policy design options lead to differences in policy costs as great as 200-400%, with clear advantages for the menu of contracts. However, different policy scenarios may strongly affect such differences. Hence, the paper calls for greater attention to the interplay between CAP scenarios and water quality measures.

Watershed-based point sources permitting strategy and dynamic permit-trading analysis

Permit-trading policy in a total maximum daily load (TMDL) program may provide an additional avenue to produce environmental benefit, which closely approximates what would be achieved through a command and control approach, with relatively lower costs. One of the important considerations that might affect the effective trading mechanism is to determine the dynamic transaction prices and trading ratios in response to seasonal changes of assimilative capacity in the river. Advanced studies associated with multi-temporal spatially varied trading ratios among point sources to manage water pollution hold considerable potential for industries and policy makers alike. This paper aims to present an integrated simulation and optimization analysis for generating spatially varied trading ratios and evaluating seasonal transaction prices accordingly. It is designed to configure a permit-trading structure basin-wide and provide decision makers with a wealth of cost-effective, technology-oriented, risk-informed, and community-based management strategies. The case study, seamlessly integrating a QUAL2E simulation model with an optimal waste load allocation (WLA) scheme in a designated TMDL study area, helps understand the complexity of varying environmental resources values over space and time. The pollutants of concern in this region, which are eligible for trading, mainly include both biochemical oxygen demand (BOD) and ammonia-nitrogen (NH3-N). The problem solution, as a consequence, suggests an array of waste load reduction targets in a well-defined WLA scheme and exhibits a dynamic permit-trading framework among different sub-watersheds in the study area. Research findings gained in this paper may extend to any transferable dynamic-discharge permit (TDDP) program worldwide.

Simultaneous optimization of dense non-aqueous phase liquid (DNAPL) source and contaminant plume remediation

A framework is developed for simultaneous, optimal design of groundwater contaminant source removal and plume remediation strategies. The framework allows for varying degrees of effort and cost to be dedicated to source removal versus plume remediation. We have accounted for the presence of physical heterogeneity in the DNAPL source, since source heterogeneity controls mass release into the plume and the efficiency of source removal efforts. We considered high and low estimates of capital and operating costs for chemical flushing removal of the source, since these are expected to vary form site to site. Using the lower chemical flushing cost estimates, it is found that the optimal allocation of funds to source removal or plume remediation is sensitive to the degree of heterogeneity in the source. When the time elapsed between the source release and the implementation of remediation was varied, it was found that, except for the longest elapsed time (50,000 days), a combination of partial source removal and plume remediation was most efficient. When first-order, dissolved contaminant degradation was allowed, source removal was found to be unnecessary for the cases where the degradation rate exceeded intermediate values of the first-order rate constant. Finally, it was found that source removal became more necessary as the degree of aquifer heterogeneity increased.

Integrated modelling of nitrate loads to coastal waters and land rent applied to catchment-scale water management

The EU Water Framework Directive (WFD) requires an integrated approach to river basin management in order to meet environmental and ecological objectives. This paper presents concepts and full-scale application of an integrated modelling framework. The Ringkoebing Fjord basin is characterized by intensive agricultural production and leakage of nitrate constitute a major pollution problem with respect groundwater aquifers (drinking water), fresh surface water systems (water quality of lakes) and coastal receiving waters (eutrophication). The case study presented illustrates an advanced modelling approach applied in river basin management. Point sources (e.g. sewage treatment plant discharges) and distributed diffuse sources (nitrate leakage) are included to provide a modelling tool capable of simulating pollution transport from source to recipient to analyse the effects of specific, localized basin water management plans. The paper also includes a land rent modelling approach which can be used to choose the most cost-effective measures and the location of these measures. As a forerunner to the use of basin-scale models in WFD basin water management plans this project demonstrates the potential and limitations of comprehensive, integrated modelling tools.

The influence of metal source uncertainty on cost-effective allocation of mine water pollution abatement in catchments

In mine water pollution abatement, it is commonly assumed that known mine waste sites are the major pollution sources, thus neglecting the possibility of significant contribution from other old and diffuse sources within a catchment. We investigate the influence of different types of pollution source uncertainty on cost-effective allocation of abatement measures for mine water pollution. A catchment-scale cost-minimization model is developed and applied to the catchment of the river Dalälven, Sweden, in order to exemplify important effects of such source uncertainty. Results indicate that, if the pollution distribution between point and diffuse sources is partly unknown, downstream abatement measures, such as constructed wetlands, at given compliance boundaries are often cost-effective. If downstream abatement measures are not practically feasible, the pollution source distribution between point and diffuse mine water sources is critical for cost-effective solutions to abatement measure allocation in catchments. In contrast, cost-effective solutions are relatively insensitive to uncertainty in total pollutant discharge from mine water sources.

Scale-up considerations for a hollow-fiber-membrane bioreactor treating trichloroethylene-contaminated water

Scale-up of a hollow-fiber-membrane (HFM) bioreactor treating trichloroethylene- (TCE-) contaminated water via co-metabolism with the methanotroph Methylosinus trichosporium OB3b PP358 was investigated through cost comparisons, bioreactor experiments, and mathematical modeling. Cost comparisons, based on a hypothetical treatment scenario of 568-L/min (150-gpm) flowrate with an influent TCE concentration of 100 microg/L, resulted in a configuration of treatment trains with two HFM modules in series and an overall annual cost of US dollar 0.36/m3 treated. Biological experiments were conducted with short lumen and shell residence times, 0.16 and 0.40 min, respectively, as a result of the cost comparisons. A new variable, specific transformation, was defined for characterizing the cometabolic transformation in continuous-flow systems, and values as large as 38.5 microg TCE/mg total suspended solids were sustainable for TCE treatment. Using mathematical modeling, HFM bioreactor system design was investigated, resulting in a five-step system design strategy to facilitate sizing of the unit processes.

Cost analysis of ELISA, solid-phase extraction, and solid-phase microextraction for the monitoring of pesticides in water

The implementation of a pesticide water monitoring program in South Africa is limited by a lack of financial and analytical resources. A cost analysis of three analytical methods, enzyme-linked immunosorbent assays (ELISA), solid-phase microextraction (SPME), and traditional solid-phase extraction methods (SPE), was conducted. The cost analysis assumed a hypothetical scenario in terms of the sampling area (a grape farming rural region in the Western Cape province of South Africa), sample collection (weekly grab samples collected from eight sites by an environmental health officer in a nearby town), transport of samples (via courier), and analysis (endosulfan and chlorpyrifos analysis conducted by a local higher educational institution laboratory in Cape Town). The cost per sample for the three analytical methods was determined by estimating the annual capital costs, including building and equipment, and recurrent costs, including transport, personnel, supplies, and building operating costs. At the optimal utility of resources, SPME had the lowest cost per sample (US $37), followed by SPE (US $48.50) and ELISA (US $60). Recurrent costs formed the bulk of the costs of all three methods (91-97%). The cost of supplies was particularly high for ELISA (US $34 per sample). The cost per sample estimated for all three methods is substantially lower than those quoted by other laboratories in South Africa. The low cost of SPME is particularly important because of the sensitivity and reliability of this method and the faster output compared to SPE, and SPME is recommended for the long-term monitoring of pesticide pollution.

Effects of water protection measures on the profitability of farms

The effect of different management measures on the nutrient losses from crop and animal husbandry systems, in particular nitrogen, and on the total income of model farming enterprises was investigated. Such measures are considered as powerful options for meeting the requirements of "cross compliance" within the Agenda 2000 midterm review of the CAP. Optimisation of the storage and handling of animal manure was shown to be the most important and cost effective measure to reduce nutrient losses on farms. Other measures such as protein and phosphorus adapted feeding, maintaining a year-round cover crop on arable land and conservation tillage were also effective and it is recommended that these are adopted into farming practices. In general, measures that have both a high potential to reduce nutrient losses and are cheap to apply, and therefore have little effect on the overall profitability of farms, should be given priority in water protection policies.

Cost-effectiveness of removing amalgam from dental wastewater

Mercury in the form of amalgam is commonly introduced into dental wastewater as a result of amalgam placements and removals. Dental wastewater is primarily discharged to municipal sewers that convey industrial and residential wastewater to publicly owned treatment works (POTWs) for treatment prior to discharge to surface waters. In some localities, the sewage sludge generated by POTWs from the treatment of wastewater is incinerated, resulting in the emission of mercury to the atmosphere. Some of the mercury emitted from the incinerators is deposited locally or regionally and will enter surface waters. An assessment was conducted of the use of mercury in amalgam in California and the discharge of that mercury from dental facilities to surface waters via the effluent from POTWs and air emissions from sewage sludge incinerators (SSIs). The annual use of mercury in amalgam placements conducted in California was estimated to be approximately 2.5 tons. The annual discharge of mercury in the form of amalgam from dental facilities to POTWs as a result of amalgam placements and removals was estimated as approximately one ton. The discharge of mercury to surface waters in California via POTW effluents and SSI emissions was estimated to total approximately 163 pounds. A cost-effectiveness analysis determined that the annual cost to the California dental industry to reduce mercury discharges to surface waters through the use of amalgam separators would range from 130,000 dollars to 280,000 dollars per pound.

Phycoremediation: key issues for cost-effective nutrient removal processes

Phycoremediation applied to the removal of nutrients from animal wastewater and other high organic content wastewater is a field with a great potential and demand considering that surface and underground water bodies in several regions of the world are suffering of eutrophication. However, the development of more efficient nutrient removal algal systems requires further research in key areas. Algae growth rate controls directly and indirectly the nitrogen and phosphorus removal efficiency. Thus, maximum algae productivity is required for effective nutrient removal and must be considered as a key area of research. Likewise, low harvesting costs are also required for a cost-effective nutrient removal system. The use of filamentous microalgae with a high autoflocculation capacity and the use of immobilized cells have been investigated in this respect. Another key area of research is the use of algae strains with special attributes such as tolerance to extreme temperature, chemical composition with predominance of high added value products, a quick sedimentation behavior, or a capacity for growing mixotrophically. Finally, to combine most of the achievements from key areas and to design integrated recycling systems (IRS) should be an ultimate and rewarding goal.

Effectiveness and reliability of arsenic field testing kits: are the million dollar screening projects effective or not?

The exposure of millions to arsenic contaminated water from hand tube wells is a major concern in many Asiatic countries. Field kits are currently used to classify tube wells as delivering arsenic below 50 microg/L (the recommended limit in developing countries) as safe, painted green or above 50 microg/L, unsafe and painted red. More than 1.3 million tube wells in Bangladesh alone have been tested by field kits. A few million U.S. dollars have already been spent and millions are waiting for the ongoing projects. However, the reliability of the data generated through field kits is now being questioned. Samples from 290 wells were tested by field kits and by a reliable laboratory technique to ascertain the reliability of field kits. False negatives were as high as 68% and false positives up to 35%. A statistical analysis of data from 240 and 394 other wells yielded similar rates. We then analyzed 2866 samples from previously labeled wells and found 44.9% mislabeling in the lower range (<50 microg/L) although mislabeling was considerably reduced in the higher range. Variation of analytical results due to analysts and replicates were pointed out adopting analysis of variance (ANOVA) technique. Millions of dollars are being spent without scientific validation of the field kit method. Facts and figures demand improved, environmentally friendly laboratory techniques to produce reliable data.