Removal of Soluble Phosphorus from Surface Water Using Iron (Fe-Fe) and Aluminum (Al-Al) Electrodes

The removal of soluble phosphorus using iron and aluminum electrodes was studied in water samples from the Red River, a hyper-eutrophic stream in Winnipeg, Canada. Four trials were conducted: (I) mixed batch with 150-900 mA applied for 1 min to 1 L, (II) stagnant batch with 600-900 mA applied for 1 min to 1 L, and (III and IV) continuously stirred-tank reactor with 6.25-10 min hydraulic retention times and constant 900 mA. Maximum soluble phosphorus removals of 70-80% were observed in mixed batch, and there was no significant difference between aluminum and iron electrodes (P value of 0.0526-0.9487). Aluminum electrodes performed significantly worse than iron electrodes under higher hydraulic loads, with iron removing >70% soluble phosphorus and aluminum <40% (P values of 0.0035-0.0143). The estimated cost of consumables, reported per million liters of water treated, to remove 70% soluble phosphorus from eutrophic waters with 0.35 g m^-3 soluble phosphorus would include 5-17.5 USD electricity costs and material costs of 5.3-12.2 USD for iron and 39.2 USD for aluminum.

Lithium, Vanadium and Chromium Uptake Ability of Brassica juncea from Lithium Mine Tailings

The potential for phytoremediation and phytostabilization of lithium in lieu with vanadium and chromium on a formulated acidic heterogeneous growth media engineered around lithium mine tailings, was investigated in four phases: (1) overall efficiency of the removal of the three metals, (2) bioaccumulation ratios of the three metals, (3) overall relative growth rate, and (4) translocation index of the three metals in the physiology of the hyperaccumulator plant. A pot study was conducted to assess the suitability of Brassica juncea (Indian mustard) in a phytoremediation process whereby it was lingered for eighty-six days under homogeneous growth conditions and irrigated bidaily with organic fertilizer amended with LiCl. A post harvest data analysis was achieved through ashing and the implementation of cold digestion procedure in a concentrated hydrochloric acidic matrix. In physiological efficiency parameters, the hyperaccumulator plant was twice as able to phytostabilize chromium and four times was able to phytostabilize vanadium in comparison to lithium. Moreover, it was extremely efficient in translocating and accumulating lithium inside its upper physiological sites, more so than chromium and vanadium, thereby demonstrating Indian mustard, as a hyperaccumulator plant, for phytoextraction and phytostabilization in an acidic heterogeneous rhizosphere, with an extremely low relative growth rate.

Modification of activated sludge properties caused by application of continuous and intermittent current

This study investigated the impact of direct current (DC) field on the activated sludge properties for potential improvement of the biological as well as membrane treatment processes. Three mixed-liquor suspended solids (MLSS) concentrations (5,000, 10,000 and 15,000 mg/l) were subjected to current densities (CD) ranging from 5 to 50 A/m² at five electrical exposure modes (time-ON/time-OFF). The results showed that CD between 15 and 35 A/m² increased the filterability of the sludge more than 200 times when compared with the untreated reference sludge. The average removals of protein, polysaccharides and organic colloids from the sludge supernatant at this range of CD were 43%, 73% and 91%, respectively, while the average reduction of the specific resistance to filtration (SRF) was 4.8 times higher. The changes of sludge properties depended on the current density, electrical exposure mode and the MLSS concentration. At CD of 25 A/m² and MLSS below 10,000 mg/l, shorter time-OFF was needed in each electrical cycle, while more time-OFF was needed at higher MLSS concentrations. It was concluded that proper application of the DC field could improve biomass in terms of its dewaterability and the removal of SMP, which are highly correlated to membrane fouling in the submerged membrane electro-bioreactor (SMEBR).

Electrically enhanced MBR system for total nutrient removal in remote northern applications

Thousands of sparsely populated communities scatter in the remote areas of northern Canada. It is economically preferable to adopt the decentralized systems to treat the domestic wastewater because of the vast human inhabitant distribution and cold climatic conditions. Electro-technologies such as electrofiltration, elctrofloatation, electrocoagulation and electrokinetic separation have been applied in water and conventional wastewater treatment for decades due to the minimum requirements of chemicals as well as ease of operation. The membrane bioreactor (MBR) is gaining popularity in recent years as an alternative water/wastewater treatment technology. However, few studies have been conducted to hyphenate these two technologies. The purpose of this work is to design a novel electrically enhanced membrane bioreactor (EMBR) as an alternative decentralized wastewater treatment system with improved nutrient removal and reduced membrane fouling. Two identical submerged membranes (GE ZW-1 hollow fiber module) were used for the experiment, with one as a control. The EMBR and control MBR were operated for 4 months at room temperature (20 ± 2 °C) with synthetic feed and 2 months at 10 °C with real sewage. The following results were observed: (1) the transmembrane pressure (TMP) increased significantly more slowly in the EMBR and the interval between the cleaning cycles of the EMBR increased at least twice; (2) the dissolved chemical oxygen demand (COD) or total organic carbon (TOC) in the EMBR biomass was reduced from 30 to 51%, correspondingly, concentrations of the extracellular polymeric substances (EPS), the major suspicious membrane foulants, decreased by 26-46% in the EMBR; (3) both control and EMBR removed >99% of ammonium-N and >95% of dissolved COD, in addition, ortho-P removal in the EMBR was >90%, compared with 47-61% of ortho-P removal in the MBR; and (4) the advantage of the EMBR over the conventional MBR in terms of membrane fouling retardation and phosphorus removal was further demonstrated at an operating temperature of 10 °C when fed with real sewage. The EMBR system has the potential for highly automated control and minimal maintenance, which is particularly suitable for remote northern applications.

Influence of electric current on bacterial viability in wastewater treatment

Minimizing the influence of electric current on bacterial viability in the electro-technologies such as electrophoresis and electrocoagulation is crucial in designing and operating the electric hybrid wastewater treatment system. In this study the biomass from a membrane bioreactor (MBR) was subjected to constant direct current and the bacterial viability was monitored against electrical intensity, duration as well as the spatial vicinity related to the electrodes. It was found that the bacterial viability was not significantly affected (less than 10% of death percentage) when the applied electric current density (CD) was less than 6.2 A/m2 after 4 h. The percentage of live cell dropped by 15% and 29% at CD of 12.3 A/m2 and 24.7 A/m2, respectively. The pH of electrolytic biomass fluid has shifted to alkaline (from nearly neutral to around pH 10) at CD above 12.3 A/m2, which could have been the contributing factor for the bacterial inactivation. The temperature change in the electrolytic media at all current densities during 4 h of experiment was less than 2 °C, thus temperature effects were negligible. Bacteria experienced different micro-environments in the electrochemical reactor. Bacterial cells on the cathode surface exhibited highest death rate, whereas bacteria outside the space between electrodes were the least affected. It was concluded that in an electro-technology integrated wastewater treatment process, sufficient mixing should be used to avoid localized inactivation of bacterial cells.

Removal of humic substances from aqueous solutions by the coagulation process

Laboratory studies were carried out on model solutions prepared on a tap-water base. The content of humic substances was 20 mg l(-1). Hardness and pH parameters of these solutions were altered using appropriate reagents. The coagulation process was run in a conventional manner using the two most popular coagulants, i.e. aluminium sulphate and iron chloride III. Optimum doses of coagulants, as well as the effect of hardness and pH of the purified solutions on coagulation process effectiveness, were determined. The efficacy of coagulation using the optimum doses of coagulants was the greatest for solutions having the highest hardness. The coagulation process progressed most efficiently in the pH range from 5 to 6. In order to describe a coagulation process with a mathematical model, the concentration of humic substances was changed from 5 to 30 mg l(-1). The results of these experiments served as a basis for the determination of the dependence of coagulant dose on the initial concentration of solutions.

Nutrient removal in an electrically enhanced membrane bioreactor

Integration of the membrane bioreactor (MBR) into wastewater treatment facilities has gained popularity in recent years due to increasingly stringent discharge permits. However, up to now no research has been conducted on the combination of nitrification, denitrification and electrochemical phosphorus removal into a MBR system. In this study a novel electrically enhanced MBR (EMBR) system was used. Without pH adjustment and external carbon source supplementation, using synthetic feed, ammonium-nitrogen was completely eliminated; COD, total nitrogen and ortho-phosphorus were removed by 94.3%, 77% and 86.6%, respectively. The power consumption was 0.22 kW/m(3) of the influent synthetic wastewater. With a control MBR run in parallel, the applied voltage gradient of 1.82 V/cm did not exhibit adverse influence on the microbial growth. This system has the potential to achieve phosphorus removal through alternating the direct current intensity.

Removal of heavy metals from oil sludge using ion exchange textiles

Development of a new simple and economic method for heavy-metal removal from oil sludge using ion exchange textiles was the main objective of this research. Three experimental stages were developed for this purpose using the bottom tank oil sludge from the Shell Canada refinery in Montreal, Canada. The first stage consisted of the direct application of ion exchange to oil sludge. The second stage included the pretreatment of oil sludge with organic solvents prior to the application of ion exchange process. The third stage included the pretreatment of oil sludge with an aqueous solution in order to extract heavy metals to the aqueous phase and then apply ion exchange textiles to the aqueous phase. Best results were obtained when acetone was used as an organic solvent leading to a total removal of vanadium while cadmium, zinc, nickel, iron, copper by 99%; 96%; 94%; 92% and 89%, respectively.

Dewatering and disinfection of aerobic and anaerobic sludge using an electrokinetic (EK) system

The objectives of the study were to upgrade sewage sludge to Class A Exceptional Quality biosolids (as defined by US EPA) using an electrokinetics dewatering system. The pathogens monitored were Salmonella spp, and fecal coliforms (FC). Ten bench-scale electrokinetic cells were set up for the disinfection of the following sludges: primary, secondary (attached growth culture and suspended culture), and anaerobically digested sludge. A conditioning liquid was also added to five cells. Blower system to aid in dewatering and drying was used in in four EK cells. Sludge characteristics such as water content, volatile solids content, sulfate and chloride ions concentrations, FC and Salmonella spp. before and after the tests were monitored. The highest total solids content (98% TS) was achieved in the cell with the low voltage gradient, in the presence of the conditioner and with the blower system. An average reduction by 50% of volatile solids was observed. The highest, 11 log-reduction of Salmonella spp. was observed in a cell with anaerobically digested sludge. No fecal coliforms were observed in any of the cells after EK treatment.

A new rapid technique for screening the potential of implanted microorganisms to tolerate and grow on petroleum oily sludges

Standard experimental protocols for biodegrading petroleum hydrocarbons employ microbiological and/or analytical analysis, and require advanced machines and specialized professionals to carry them out. Furthermore, the obtained results involve a high margin of error. In this paper, a new experimental technique was developed to facilitate the study of microbial capability to degrade petroleum oily sludges. The technique is based on growing microorganisms on 0.22 microm filter membranes laid over oily sludge placed in metallic cups. The microbial growth was assessed using the plate counts technique. Sludge degradation was assessed using Fourier Transform Infrared Spectrometry (FTIR), and compared to the decrease in total petroleum hydrocarbons (TPH) using solvent extraction. The protocol was tested using three types of inocula: fungal inoculum containing Paecilomyces variotii; bacterial inoculum containing Bacillus cereus; and fungal-bacterial inoculum containing both strains. Both, fungal and bacterial, strains were isolated from the oily sludge used in the present study, and were tentatively identified as oil degraders. The results of the newly developed technique helped to assess the potential of these cultures to tolerate and grow on the oily sludge.