Removal and recovery of nutrients as struvite from anaerobic digestion residues of poultry manure

The removal and the recovery of nutrients, namely nitrogen (N) and phosphorus (P) from anaerobically digested and solid-liquid separated manure effluents via struvite precipitation were investigated. Both the liquid and the solid phases of the poultry manure digester effluent were subjected to struvite precipitation experiments. The Mg:N:P molar ratio of 1:1:1 in the liquid phase resulted in an average NH4-N removal efficiency of 86.4%, which increased to 97.4% by adjusting the Mg:N:P ratio to 1.5:1:1. The acidic phosphorus-dissolution process was applied to the solid phase of the effluent to obtain a phosphorus-enriched solution. Nutrient recovery experiments with NaOH as the buffering reagent were conducted with and without addition of external chemicals (Mg and P sources) to evaluate the influence of the Mg:N:P molar ratio, the Mg:P molar ratio and pH. All the experiments depicted complete PO4-P (99.6-100.0%) and partial NH4-N (3.3-65.6%) recoveries from the phosphorus-enriched solution.

Modification of a conventional anaerobic digester for improving the effluent and sludge characteristics

The aim of this study was to enrich the composition of anaerobic digester sludge in terms of nitrogen and phosphorus by struvite (MgNH4PO4) formation. Waste activated sludge was anaerobically digested in batch reactors under the conditions that the minimum stoichiometric requirement for struvite formation was satisfied in all reactors. For this purpose, different amounts of magnesium (Mg2+) and phosphate (PO4(3-)) ions were added initially to the batch reactors. The results showed the effects of adding Mg2+ and PO4(3-) ions on the performance of anaerobic digestion and on the amounts of ammonium (NH4+) and PO4(3-) ions released during digestion. The results indicated that the performance of the anaerobic digestion in chemical oxygen demand removal changed between -4.0% and 15.4% for a Mg2+ concentration range of 277.2 to 529.3 mg/L and a PO4(3-) concentration range of 377.4 to 2372.4 mg/L. There was an increase in the concentration of NH4+ in all reactors during digestion, but the extent of concentration increase could be controlled by increasing the initial concentrations of Mg2+ and PO4(3-). The maximum removal of NH4+ ions (33.7%) was observed in the reactor dosed initially by Mg2+ and PO4(3-) concentrations of 467.2 and 2123.3 mg/L, respectively. The concentration of PO4(3-) ion was lower than its initial concentration in all reactors, indicating considerable fixation of PO4(3-) as it was released, by struvite and other solid species formation. The decrease in the concentration of Mg2+ ions similar to PO4(3-) was accepted as evidence for the formation of solid species composed of Mg2+ and PO4(3), in addition to struvite. Water

Performance of leaching bed reactor converting the organic fraction of municipal solid waste to organic acids and alcohols

A lab-scale leaching bed reactor (LBR) was operated to (1) investigate the potential of in-vessel solid-state anaerobic digestion of the organic fraction of municipal solid waste (MSW) and (2) examine the feasibility of using LBRs for hydrolysis/liquefaction and acidification of organic fraction of MSW for maximum total volatile fatty acid (tVFA) and alcohol production. A hydrolysis efficiency of 60% was achieved in the LBR, which was mainly affected by the solids content of organic fraction of MSW, the amount of water addition into the LBR and the channeling through the waste bed. The net mass of tVFA produced was 7000 mg at the end of 80 d. The main individual VFAs produced were acetic and butyric acids and the main alcohol was ethanol. The variations in the by-products of acidification were mainly due to the nature of feed and pH variations in the LBR. LBRs achieved rapid hydrolysis and acidification of organic fraction of MSW, consequently, high hydrolysis yield, chemical oxygen demand removal and tVFA production.

Anaerobic biogasification of undiluted dairy manure in leaching bed reactors

Dry anaerobic digestion of high solids animal manure is of increasing importance since conventional slurry digestion is not an effective system for these manures. The investment costs for large-size reactors, costs for heating these reactors, handling, dewatering, and the disposal of the digested residue decrease the benefits of conventional slurry anaerobic digestion for high solids animal manure. Even though leaching bed reactors (LBR) constitute a promising option for dry anaerobic biogasification of animal manure, no study is cited in the literature for animal manure, excluding a single study on cattle waste which utilized a similar concept in a different experimental set-up, namely a packed bed digester. Therefore, this work was undertaken to investigate the anaerobic biogasification of undiluted dairy manure in LBRs. To this purpose anaerobic leaching bed reactors (ALBR) packed with a mixture of dairy manure, anaerobic seed and wood powder/chips were operated. The ALBRs were fed with water, and the leachate that was collected from their effluents was subjected to biochemical methane potential (BMP) experiments to determine the biogas production. The results revealed that LBRs can successfully be applied to anaerobic digestion of undiluted dairy manure with around 25% improvement in biogas production relative to conventional (slurry) anaerobic digesters.

Anaerobic digestion of dairy manure with enhanced ammonia removal

Poor ammonia-nitrogen removal in methanogenic anaerobic reactors digesting animal manure has been reported as an important disadvantage of anaerobic digestion (AD) in several studies. Development of anaerobic processes that are capable of producing reduced ammonia-nitrogen levels in their effluent is one of the areas where further research must be pursued if AD technology is to be made more effective and economically advantageous. One approach to removing ammonia from anaerobically digested effluents is the forced precipitation of magnesium ammonium phosphate hexahydrate (MgNH4PO4 x 6H2O), commonly called struvite. Struvite is a valuable plant nutrient source for nitrogen and phosphorus since it releases them slowly and has non-burning features because of its low solubility in water. This study investigated coupling AD and controlled struvite precipitation in the same reactor to minimize the nitrogen removal costs and possibly increase the performance of the AD by reducing the ammonia concentration which has an adverse effect on anaerobic bacteria. The results indicated that up to 19% extra COD and almost 11% extra NH3 removals were achieved relative to a control by adding 1750 mg/L of MgCl2 x 6H2O to the anaerobic reactor.

Cleaner production opportunity assessment for a milk processing facility

Possible cleaner production (CP) opportunities for a milk processing facility were examined in this study. The CP concept and its key tools of implementation were used to assess the potential CP opportunities in the facility studied. The general production process and its resulting environmental loads were investigated by taking possible CP opportunities as the basis of study. The methodology developed for CP opportunity assessment in the milk processing facility covered two major steps: preparation of checklists to assist auditing and CP opportunity assessment, and implementation of the mass-balance analysis. For mass-balance analysis, measurements and experimental analysis of the mass flows were utilized to determine the inputs and outputs. Prepared checklists were utilized to determine waste reduction options that could be implemented. Selected opportunities were evaluated considering their environmental benefits and economic feasibility. The results of the study indicated that 50% of the service water used, 9.3% of the current wastewater (WW) discharge, 65.36% of the chemical use and the discharge of 181.9 kg/day of chemical oxygen demand (COD) and 20.7 kg/day of total suspended solids (TSS) could be eliminated and 19.6% of the service water used could be recycled/reused.

Life cycle assessment of municipal solid waste management methods: Ankara case study

Different solid waste management system scenarios were developed and compared for the Municipal Solid Waste Management System of Ankara by using the life cycle assessment (LCA) methodology. The solid waste management methods considered in the scenarios were collection and transportation of wastes, source reduction, Material Recovery Facility (MRF)/Transfer Stations (TS), incineration, anaerobic digestion and landfilling. The goal of the study was to determine the most environmentally friendly option of MSWM system for Ankara. The functional unit of the study was the amount of solid waste generated in the system area of concern, which are the districts of Ankara. The life cycle inventory analysis was carried out by IWM Model-1. The inputs and outputs of each management stage were defined and the inventory emissions calculated by the model were classified in to impact categories; non-renewable energy sources exhausting potential, final solid waste as hazardous and non-hazardous, global warming, acidification, eutrophication and human toxicity. The impacts were quantified with the weighing factors of each category to develop the environmental profiles of each scenario. In most of the categories, Source Reduction Scenario was found to be the most feasible management method, except the global warming category. The lowest contribution to GWP was calculated for the anaerobic digestion process. In the interpretation and improvement assessment stage, the results were further evaluated and recommendations were made to improve the current solid waste management system of Ankara.

Control of trichloroethylene emissions from sparging systems by horizontal bio- and chemo- barriers

The scope of this study was to develop a continuous system to clean-up a trichloroethylene (TCE) contaminated gas stream, where biotic and abiotic removal mechanisms are undertaken sequentially simulating the horizontal bio- and chemo-barriers proposed for the in-situ remediation of the contaminated sites. The bio- and chemo-barriers were simulated by using glass columns packed with granular anaerobic mixed culture and Fe(0) filings, respectively. The effect of gas residence time, which is adjusted by the gas flowrate, on the TCE removal efficiency of the reactor system was investigated. TCE removal efficiency of over 90% was achieved at gas residence times above 1hr. Furthermore, the effluent of reactor system contained only ethane and ethylene, which are non-toxic by-products of TCE reduction reactions, along with trace amounts of TCE.

Anaerobic treatment of real textile wastewater with a fluidized bed reactor

Anaerobic treatability of a real cotton textile wastewater was investigated in a fluidized bed reactor (FBR) with pumice as the support material. The immobilized biomass or attached volatile solids level on the support material was 0.073 g VSS/g support material at the end of the 128-d start-up period. During the operation period, real cotton textile wastewater was fed to the anaerobic FBR both unsupplemented (in Stages 1 and 2) and supplemented (with synthetic municipal wastewater in Stage 3 and glucose in Stages 4-6). The effect of operational conditions such as organic loading rate (OLR), hydraulic retention time (HRT), influent glucose concentration as the co-substrate, etc. was investigated to achieve the maximum color removal efficiency in the reactor. Results indicated that anaerobic treatment of textile wastewater studied was possible with the supplementation of an external carbon source in the form of glucose (about 2g/l). The corresponding maximum COD, BOD(5) and color removals were found to be around 82%, 94% and 59%, respectively, for HRT of around 24h and OLR of 3 kg COD/m(3)/d. Further increase in external carbon source added to real textile wastewater did not improve the color removal efficiency of the anaerobic FBR reactor.

The inhibitory effects of lindane in batch and upflow anaerobic sludge blanket reactors

In this study, the inhibitory effects of lindane (LIN) on originally unacclimated mixed anaerobic cultures were investigated by anaerobic toxicity assay (ATA) experiments. ATA experiments revealed that 10 mg/l LIN exerted inhibitory effects on anaerobic cultures, which was recoverable. Continuous reactor experiments conducted to determine the inhibitory effects of LIN and the maximum LIN loading rate achievable in two-stage upflow anaerobic sludge blanket (UASB) reactors indicated that anaerobic granular cultures were successfully acclimated to 30 mg/l LIN. The maximum LIN loading rate and minimum hydraulic retention time (HRT) possible for the UASB system were 10 mg/l day and 18 h, respectively, which resulted in the overall chemical oxygen demand (COD) removal efficiency of 89%.

Anaerobic treatability and biogas production potential studies of different agro-industrial wastewaters in Turkey

The anaerobic treatability and methane generation potential of the wastewaters of the three important agro-industries in Turkey, namely, cheese-making, poultry breeding and the olive-oil mill industries were studied. Biochemical methane potential (BMP) experiments were conducted for different initial chemical oxygen demand (COD) concentrations. The results indicate that anaerobic treatment was possible for all the wastewaters studied and the biogas produced had a high methane content.

Comparison of methods for estimating carbonaceous BOD parameters

The performance of seven different methods (Differential, Fujimoto, Thomas, Graphical, Integral, Log-Difference, and Nonlinear Regression) for estimating first-stage, carbonaceous biochemical oxygen demand (CBOD), curve parameters, namely k and L0, were compared using synthetic data generated by Monte Carlo simulation technique. The comparison of the methods was made based on their efficiency in retrieving the original values of k and L0, which were selected to generate the synthetic data. In the first part of the study, five sets of "true" data (without error substitution) with different k and L0 value pairs, (k (d(-1))-L0 (mg l(-1)): 0.23-10,000; 0.23-250; 0.23-50; 0.10-250; and 0.50-250) were used to obtain information about the effect of different k-L0 combinations and of using 5-day and 20-day CBOD data on the performance of the methods. In the second part, the same methods were used to calculate k and L0 for ten sets of synthetic data with log-normally distributed random errors at the coefficient of variation (COV) levels of 0.1, 0.2, and 0.3 for a single k-L0 value pair, (0.23 d(-1); 250 mg l(-1)). The results indicated that: (1) different combinations of k-L0 values had no significant effect on the performance of CBOD curve parameter estimation methods with the "true" data; (2) use of CBOD20 data, i.e., CBOD data collected for 20 days, provided better estimates for k and L0; (3) the Integral and Nonlinear Regression techniques were found to be the most reliable methods for the estimation of CBOD curve parameters among the other methods considered in this study.

Sequential (anaerobic/aerobic) biological treatment of Dalaman SEKA pulp and paper industry effluent

In the pulp and paper industry, lignin and other color compounds are removed by chemical agents in bleaching process. Use of chlorine-based agents results in production of degradation products which include various chloro-organic derivatives. Since these new compounds are highly chlorinated, they cause a problem in the treatment of pulp and paper industry wastewaters. Chemical precipitation, lagooning, activated sludge, and anaerobic treatment are the processes used for treating pulp and paper effluents. Furthermore, a combination of these processes is also applicable. In this study, the effluent of Dalaman SEKA Pulp and Paper Industry was examined for its toxic effects on anaerobic microorganisms by anaerobic toxicity assay. Additionally, this wastewater was applied to a sequential biotreatment process consisting of an upflow anaerobic sludge blanket as the anaerobic stage and a once-through completely mixed stirred tank as the aerobic stage. Results indicated that: (1) Dalaman SEKA Pulp and Paper Industry wastewater exerted no inhibitory effects on the anaerobic cultures under the studied conditions, and (2) application of a sequential biological (anaerobic/aerobic) system to treat the Dalaman SEKA Pulp and Paper Industry wastewater resulted in approximately 91% COD and 58% AOX removals at a HRT of 5 and 6.54 h for anaerobic and aerobic, respectively.

Anaerobic biotransformation and methane generation potential of cheese whey in batch and UASB reactors

Anaerobic treatability and methane generation potential of cheese whey were determined in batch reactors. Furthermore, the effect of nutrient and trace metal supplementation on the batch anaerobic treatment, and the high-rate anaerobic treatability of cheese whey in upflow anaerobic sludge blanket (UASB) reactors were investigated. To this purpose biochemical methane potential experiments were conducted and single- and two-stage UASB reactors with granular cultures were operated. In UASB experiments significance of process staging, operational parameters such as hydraulic retention time (HRT), influent chemical oxygen demand (COD) concentration and loading rate were also investigated. The results revealed that nutrient and trace metal supplementation is vital for the anaerobic treatment of cheese whey; the anaerobic methane generation for the cheese whey studied was found to be 424 ml CH4/g COD (23.4 1 CH4/l cheese whey); undiluted cheese whey could be treated anaerobically at relatively short HRT values (2.06-4.95 days) without any significant stability problems; HRT values as low as 2-3 days can be used for the anaerobic treatment of cheese whey, with a COD removal efficiency of 95-97% at influent COD concentration of 42 700 +/- 141-55 100 +/- 283 mg/l.

Effectiveness of anaerobic biomass in adsorbing heavy metals

This study focuses on the effectiveness of waste anaerobic dead biomass (ADB) in adsorbing heavy metals, namely Pb(II), Cr(VI), Cu(II), Ni(II) and Zn(II). The metal uptake capacity of ADB was investigated and compared with the values for various biomass types from the literature. The biomass, which was grown under laboratory conditions using a synthetic wastewater, was used throughout the study after sterilization. The maximum metal adsorptive capacities were evaluated by running isotherm tests at 25 degrees C and initial pH of 4. It was observed that Pb(II) was adsorbed with the highest capacity. The maximum adsorptive capacity of ADB for Pb(II), Zn(II), Cu(II), Ni(II) and Cr(VI) was determined as 1250, 625, 357, 227 and 384 mg/g dry biomass, respectively. These values were significantly higher than the corresponding capacities reported in the literature for other types of biomass. In describing the adsorption equilibrium, both the Langmuir and Freundlich isotherm models were examined. The experimental data for Pb(II), Zn(II), Cr(VI), and Ni(II) fitted both the Langmuir and Freundlich models with correlation coefficients of 0.80-0.99 while Cu(II) only fitted the Langmuir model with a correlation coefficient of 0.99. Therefore, different and distinct aspects of the interactions between the cell surfaces and the metal ions might have occurred for Cu(II) and the rest of the metals. The equilibrium pH values attained were all higher than the initial pH value of 4.0, and this indicated that both the type and the initial concentration of the metal influenced the equilibrium pH. Furthermore, there was a decrease in equilibrium pH with increasing initial metal concentration at varying levels.

Inhibitory effects and biotransformation of acrylic acid in computer-controlled pH-stat CSTRs

In this study, the inhibitory effects and anaerobic biotransformation of acrylic acid in computer-controlled pH-stat completely stirred tank reactors (CSTRs) with two different cultures, namely unacclimated and acrylate-acclimated acetate-enriched Methanosarcina and homogenized (crushed) granular cultures, were investigated. The microbial acclimation, influent concentration, and loading rate of acrylic acid were studied in the experiments. The experimental results revealed that methanogenic cultures at a concentration of 3200 +/- 80 mg/L as volatile suspended solids (VSS) could be acclimated to acrylic acid up to a loading rate of 220 mg/L per day (0.068 g acrylic acid/g VSS per day) in the presence of a constant acetate concentration of 2000 +/- 200 mg/L as the primary substrate after 300 days of acclimation. The same cultures (680 +/- 80 mg/L as VSS), after 80 days of acclimation to acrylic acid as the sole carbon source, transformed acrylic acid up to the loading rate of about 200 mg/L per day (0.29 g acrylic acid/g VSS per day) almost completely (>99%) to acetic and propionic acid, but could not effectively metabolize these intermediate products. Acrylate-acclimated homogenized granular cultures (6900 +/- 80 mg/L as VSS) effectively metabolized 2200 mg/L per day (0.32 g acrylic acid/g VSS per day) of acrylic acid, as the sole carbon source, after 50 days of severe inhibition.