Bioremediation of leachate from a green waste composting facility using waste-derived filter media

The evaluation of two waste-derived materials used to treat compost leachate by biofiltration is described in this paper. Nine biofilters were constructed using 240 l, high density polyethylene containers. Three containers were filled without compaction with 200l of each of three types of filter media. Waste-derived filter media (compost and oversize) were compared to a mineral control (granite chips). The filters were fed with compost leachate from a typical green waste composting facility at hydraulic loading rates ranging from 0.05 m3/m3/day to 0.5 m3/m3/day over a period of twelve months. The oversize medium emerged as the most effective demonstrating characteristics of consistency of effluent quality and resilience to stress. The oversize medium produced an effluent of <10mg/l ammoniacal nitrogen on >95% of sampling occasions. The organic component of compost leachate was dominated by compounds that proved to be recalcitrant to biodegradation. The solids content of the treated effluent remained too high to be acceptable for direct discharge to a watercourse without further treatment and if discharge to a watercourse is to be considered, a polishing stage (e.g., reed bed) able to remove solids and dampen occasional peaks of ammoniacal nitrogen should be employed.     

Adsorption, absorption, and biological degradation of ammonia in different biofilter organic media

A tailor-made apparatus called ammoniometer, which is a batch mode respirometer applied to the study of ammonia biodegradation in biofilter media, has been used to evaluate adsorption, absorption, and biodegradation in five different organic materials (compost, coconut fibre, bark, pruning wastes, and peat) obtained from full-scale biofilters in operation in several waste treatment plants. The results showed that absorption could be represented by a Henry's law linear equation, with values of the Henry coefficient significantly higher (from 1,866 to 15,320) than that of pure water (1,498). Adsorption data were successfully fitted to Langmuir and Freundlich isotherms and maximum adsorption capacity varies from 1.06 to 1.81 mg NH(3)/g dry media. Ammonia biodegradation rates for each organic material were also calculated. Biodegradation rates varied from 0.67 to 7.82 mg NH(3)/kg media/d depending on the material tested. The data obtained showed important differences in the behaviour of the biofilter organic media, which has important implications in the design and modelling of these systems.     

Treatment of leachate from a solid waste landfill site using a two-stage anaerobic filter

Raw leachate was treated using a two-stage upflow anaerobic filter process. Leachate from a solid waste landfill site, which received both municipal and industrial wastes, contained high organic matter (17-21 g/L COD, 13-14 g/L BOD, and 3.5-4.6 g/L volatile acids), and low metal (Zn and Fe) concentrations. Depending on sampling time, leachate composition and characteristics varied considerably. At an organic loading up to 4 g COD/day(2) media area, the BOD and COD removal percentages were 98 and 91%, respectively. The biofilters were also effective for metal removal. However, the filter effluent contained a high concentration of ammonia. System overloading was characterized by the accumulation of large quantities of volatile acids and by a now ratio of alkalinity/volatile acids, resulting in low COD removal and reduced gas production. Once the first filter was upset, the second stage could only partially respond to the volatile acids accumulated in the effluent of first filter.     

Fungal biocatalysts in the biofiltration of VOC-polluted air

Gas-phase biofilters used for the treatment of waste gases were originally packed with compost or other natural filter beds containing indigenous microorganisms. Over the past decade much effort has been made to develop new carrier materials, more performant biocatalysts and new types of bioreactors. Elimination capacities reached nowadays are 5 to 10 times higher than those originally reported with conventional compost biofilters. With the recently developed inert filter beds, inoculation is a prerequisite for successful start-up and operation. Either non-defined mixed cultures or pure bacterial cultures have originally been used. The search for efficient fungal biocatalysts started only a few years ago, mainly for the biofiltration of waste gases containing hydrophobic compounds, such as styrene, alpha-pinene, benzene, or alkylbenzenes. In this review, recently isolated new fungal strains able to degrade alkylbenzenes and other related volatile organic pollutants are described, as well as their major characteristics and their use as biocatalysts in gas-phase biofilters for air pollution control. In biofiltration, the most extensively studied organism belongs to the genus Exophiala, although strains of Scedosporium, Paecilomyces, Cladosporium, Cladophialophora, and white-rot fungi are all potential candidates for use in biofilters. Encouraging results were obtained in most of the cases in which some of those organisms were present in gas-phase biofilters. They allow reaching high elimination capacities and are resistant to low pH values and to reduce moisture content.     

Treatment of wastewater containing Cl2 residue by packed cage rotating biological contactor (RBC) system

A packed cage rotating biological contactor (RBC) system was applied to treat wastewater containing Cl2 residue with concentration even up to 20 mg/L. However, Cl2 exhibited a negative effect on the efficiency of the system as evidenced by the decrease in the growth of bio-film. It could be concluded that the removal efficiency of the system decreased with the increase of Cl2 concentration or Cl2 loading. Due to inhibition of bio-film growth by the effects of Cl2 residue, the effluent suspended solids (SS) of the system was decreased. The bio-film was easily detached from the media under high growth rate conditions resulting in an increase of effluent SS. The COD and BOD5 removal efficiencies of the system under the highest organic and Cl2 loadings of 4.07 g BOD5/m2 d and 203.6 mg Cl2/m2 d, respectively, were 58.0+/-3.2% and 60.7+/-3.9%, respectively, while they were up to 83.3+/-1.8% and 85.8+/-2.0%, respectively, under the lowest organic and Cl2 loading of 2.04 g BOD5/m2 d and 25.5 mg Cl2/m2 d. However, the effluent SS of the system under above operating conditions was lower than 20 mg/L.     

Combined biological and membrane treatment of food-processing wastewater to achieve dry-ditch criteria: pilot and full-scale performance

This study tested the applicability of a submerged vacuum ultrafiltration membrane technology in combination with the biological treatment system to achieve dry-ditch criteria stipulated as follows: BOD5, TSS, NH3-N, and total phosphorous (TP) concentration not exceeding 10, 10, 1, and 0.5 mg/L respectively for the treatment of high strength food-processing wastewater. During the study, the biological system, operated at average hydraulic retention time of 5-6 days, achieved 95-96.5% BOD removal and 96-99% COD removal. The external membrane system ensured the achievability of the BOD and TSS criteria, with BOD and TSS concentrations in the permeate of 1-2 and 1-8 mg/L respectively. Nitrate, and nitrite concentrations increased during membrane filtration, while ammonia concentrations decreased. The most salient finding of this study is that, contrary to common belief, for industrial wastewaters, the filterability of the mixed liquor is influenced by the soluble organics, and may be low, thus necessitating operation of bioreactors at low mixed liquor solids. This study demonstrated that bioreactors operated at low SRTs and in combination with ultrafiltration can still achieve superior effluent quality that may meet reuse criteria at reasonable cost.     

Anaerobic treatment of pre-hydrolysate liquor (PHL) from a rayon grade pulp mill: pilot and full-scale experience with UASB reactors

Pilot studies were carried out for the treatment of pre-hydrolysate liquor (PHL), a high strength effluent (COD: 70,000-80,000 mg/l) emanating from a rayon grade pulp mill using up-flow anaerobic sludge blanket reactor (UASB). Substrate inhibition was avoided with optimum COD feed of around 25,000 mg/l. This was achieved by diluting the PHL with a low strength effluent stream known as alkali back wash (ABW) available in the plant and also by partially recycling the reactor liquid outlet. An optimum organic loading rate (OLR) of 10 could be achieved with a COD reduction of 70-75%, a BOD reduction of 85-90% and a methane yield of 0.31-0.33 m3/kg of COD reduced. The pilot scale studies also revealed that addition of milk of lime (MOL) was essential for neutralization and buffering and DAP and urea to supplement the nutrients in the PHL. Based on the pilot studies, a full-scale high rate biomethanation plant was designed and erected for treating the PHL, which after some modification showed similar performance for COD, BOD reduction and methane yield.     

Treatment of tomato processing wastewater by an upflow anaerobic sludge blanket-anoxic-aerobic system

The main objective of this study is to assess the achievability of stringent discharge criteria i.e. BOD(5)<15 mg/L, TSS<15 mg/L and NH(4)-N<1mg/L during the treatment of tomato processing wastewater with COD of 2800-15,500 mg/L, BOD(5) of 1750-7950 mg/L, TKN of 48-340 mg/L and NH(4)-N of 21-235 mg/L. Two treatment systems, a UASB-aerobic system and a UASB-anoxic-aerobic system were tested. Furthermore due to alkalinity deficiency, in the raw wastewater, the study explored varying UASB effluent recirculation flowrates to the UASB influent to reduce additional alkalinity requirements. The UASB-anoxic-aerobic system was effective in treating tomato canning wastewater at an overall HRT of 1.75 days while achieving 98.5% BOD(5), 95.6% COD, 84% TSS and 99.5% NH(4)-N removal producing effluent BOD(5), COD, TSS, NH(4)-N, TKN, NO(2)-N, NO(3)-N and PO(4)-P of 10, 70, 15, 0.5, 3, 0, 60 and 4 mg/L, respectively. The biogas yield was 0.43 m(3)/kg COD removed.     

Treatment of hydroponic wastewater by denitrification filters using plant prunings as the organic carbon source

This study investigated the feasibility of using pre-treated plant liquors as organic carbon sources for the treatment of hydroponic wastewater containing high nitrate-N (>300 mg N/L). The waste plant material was pre-treated to extract organic carbon-rich liquors. When this plant liquor was used as an organic carbon source in denitrification filters at the organic carbon:nitrogen dose rate of 3C:N, nitrate removal efficiencies were >95% and final effluent nitrate concentrations were consistently <20mg N/L. However, at this dose rate, relatively high concentrations (>140 mg/L) of organic carbon (fBOD5) remained in the final effluents. Therefore, a 'compromise' organic carbon:nitrogen dose rate (2C:N) was trialled, at which nitrate removal efficiencies were maintained at >85%, final effluent nitrate concentrations were consistently below 45 mg N/L, and effluent fBOD5 concentrations were <25mg/L. This study has demonstrated that waste plant material is a suitable carbon source for the removal of nitrate from hydroponic wastewater in a denitrification filter.     

Microbiological and molecular characterization of denitrification in biofilters treating pig manure

Aerated organic biofilters treating pig manure exhibit partial nitrogen removal. In order to optimize this process, a better comprehension of its colonization by denitrifiers was needed. Three pilot aerated biofilters, fed with variable Biological Oxygen Demand after five days: Total Kjeldahl Nitrogen (BOD(5):TKN) ratios, were constructed and monitored during 180 days. Nitrogen was analyzed in the gaseous and liquid flows, at different depths in the systems. Denitrifying biomass was characterized by evaluating its observed (nitrogen mass balances) and potential (adapted acetylene inhibition technique) activities and its quantity (real-time PCR on nirS), at different heights inside the biofilters. Denitrification was observed as soon as nitrate was produced by nitrifiers, after approximately 40 days of operation, but the potential to denitrify increased from the beginning of the monitoring period. Biofilter fed with the highest BOD(5):TKN ratio showed significant differences with the others, particularly after 80 days of operation, as its potential activity was lower with a higher observed nitrate removal. Data showed that denitrifiers were mainly localized near the surface of the filter and that a microbiological gradient was present from top to bottom. The potential denitrifying activities were always higher than what was being observed inside the sections studied, suggesting that the biomass could have reduced more nitrate and that conditions found inside the filter did not allow denitrification to completely occur.     

Biofiltration of composting gases using different municipal solid waste-pruning residue composts: monitoring by using an electronic nose

The concentration of volatile organic compounds (VOCs) during the composting of kitchen waste and pruning residues, and the abatement of VOCs by different compost biofilters was studied. VOCs removal efficiencies greater than 90% were obtained using composts of municipal solid waste (MSW) or MSW-pruning residue as biofilter material. An electronic nose identified qualitative differences among the biofilter output gases at very low concentrations of VOCs. These differences were related to compost constituents, compost particle size (2-7 or 7-20 mm), and a combination of both factors. The total concentration of VOCs determined by a photoionization analyser and inferred from electronic nose data sets were correlated over an ample range of concentrations of VOCs, showing that these techniques could be specially adapted for the monitoring of these processes.     

Compost product optimization for surface water nitrate treatment in biofiltration applications

Compost based material has been proposed for use as media for biofiltration for environmental restoration in many areas to remediate contaminated water and soil. The objective of this project was to develop techniques to produce compost products for nitrate removal in storm water biofiltration applications, from typical solid waste materials. Compost products were manufactured from different feedstocks and evaluated for their nitrate removal efficiencies. Three different compost products manufactured from varying feedstock amounts of wood chips and grass clippings, along with some dry compost material from the City of Brownsville Municipal Landfill Facility (BMLF), were evaluated using column studies. Indicators of the compost product’s quality included moisture % content, pH, and conductivity measurements. The columns were loaded with water containing at least 13.5 mg/L nitrate–nitrogen and effluent water from the columns was tested to determine the nitrate reduction for the different products. All of the manufactured compost products and the BMLF material removed some nitrate. The project demonstrated that compost product materials can be effectively used for some nitrate removal for surface water quality improvement and that compost product feedstocks and blends can influence the materials capability for nitrate removal.     

汉沽化工废水渔业利用的研究

汉沽化工废水成分复杂,含有较高浓度的BOD_5,COD,NH_3-N、PO_4-P、氯化物、汞等。经多级模拟生物氧化塘处理后,废水得到有效净化。净化后的污水,因氯化物浓度过高不宜用于农灌。但可用于养鱼,进行综合利用,实现污水资源化。 在净化后污水中进行罗非鱼(Tilapia mossambica)养殖实验,历时132天。在未人工投饵的情况下,试鱼生长、繁殖正常,而且肌肉中汞的积累不明显,最高汞含量变化在0.35—0.40μg/g之间,接近食用要求。 污水中藻类等饵料生物丰富,生物生产力较高。在浮游植物生产量和底栖动物生物量的基础上,估算了改建后污水库鱼类的生产能力。 鱼类养殖是氮、磷丰富的台盐、含汞化工废水回用和生物去氮,去磷的重要途径。而且是含汞废水净化效果的重要指标。     

Methods for Facilitating Microbial Growth on Pulp Mill Waste Streams and Characterization of the Biodegradation Potential of Cultured Microbes

The kraft process is applied to wood chips for separation of lignin from the polysaccharides within lignocellulose for pulp that will produce a high quality paper. Black liquor is a pulping waste generated by the kraft process that has potential for downstream bioconversion. However, the recalcitrant nature of the lignocellulose resources, its chemical derivatives that constitute the majority of available organic carbon within black liquor, and its basic pH present challenges to microbial biodegradation of this waste material. Methods for the collection and modification of black liquor for microbial growth are aimed at utilization of this pulp waste to convert the lignin, organic acids, and polysaccharide degradation byproducts into valuable chemicals. The lignocellulose extraction techniques presented provide a reproducible method for preparation of lignocellulose growth substrates for understanding metabolic capacities of cultured microorganisms. Use of gas chromatography-mass spectrometry enables the identification and quantification of the fermentation products resulting from the growth of microorganisms on pulping waste. These methods when used together can facilitate the determination of the metabolic activity of microorganisms with potential to produce fermentation products that would provide greater value to the pulping system and reduce effluent waste, thereby increasing potential paper milling profits and offering additional uses for black liquor.     

Appraising bacterial strains for rapid BOD sensing—an empirical test to identify bacterial strains capable of reliably predicting real effluent BODs

The measured response of rapid biochemical oxygen demand (BOD) biosensors is often not identical to those measured using the conventional 5-day BOD assay. This paper highlights the efficacy of using both glucose–glutamic acid (GGA) and Organisation for Economic Cooperation and Development (OECD) BOD standards as a rapid screen for microorganisms most likely to reliably predict real effluent BODs when used in rapid BOD devices. Using these two synthetic BOD standards, a microorganism was identified that produced comparable BOD response profiles for two assays, the MICREDOX® assay and the conventional 5-day BOD₅ test. A factorial experimental design systematically evaluated the impact of four factors (microbial strain, growth media composition, media strength, and microbial growth phase) on the BOD response profiles using GGA and OECD synthetic standard substrates. An outlier was identified that showed an improved correlation between the MICREDOX® BOD (BOD_sens) and BOD₅ assays for both the synthetic standards and for real wastewater samples. Microbial strain was the dominant factor influencing BOD_sens values, with Arthrobacter globiformis single cultures clearly demonstrating superior rapid BOD_sens response profiles for both synthetic and real waste samples. It was the only microorganism to approach the BOD₅ response for the OECD substrate (171 mg O₂?L^?1), and also reported BOD values for real waste samples that were comparable to those produced by the BOD₅ test, including discriminating between filtered and unfiltered samples.     

Enhanced removal of organic matter and ammoniacal-nitrogen in a column experiment of tidal flow constructed wetland system

A tidal flow constructed wetland system was investigated for the removal of organic matter and ammoniacal-nitrogen from diluted piggery wastewater. The results demonstrated that the operation of tidal flow enhanced the transfer of oxygen into wetland matrices. The supply of oxygen by the operation (473 gO2/m2d) matched the demand for wastewater treatment. The overall oxygen consumption rate in the system was considerably higher than the typical rate obtainable in conventional wetlands; most oxygen being used for the decomposition of organic matter. Compared with conventional systems, the tidal flow system demonstrated greater efficiency in the removal of organic matter. Significant nitrification did not take place, although 27-48% ammonia was removed from the wastewater. Immobilization by microbial cells and adsorption were the likely routes to remove ammonia under the specific experiment conditions. Percentage removals of BOD5, NH4-N and SS increased after effluent recirculation at a ratio of 1:1 was employed.     

Anaerobic treatment of distillery spent wash - a study on upflow anaerobic fixed film bioreactor

Anaerobic digestion of wastewater from a distillery industry having very high COD (1,10,000-1,90,000 mg/L) and BOD (50,000-60,000 mg/L) was studied in a continuously fed, up flow fixed film column reactor using different support materials such as charcoal, coconut coir and nylon fibers under varying hydraulic retention time and organic loading rates. The seed consortium was prepared by enrichment with distillery spent wash in a conventional type reactor having working capacity of 3 L and was used for charging the anaerobic column reactor. Amongst the various support materials studied the reactor having coconut coir could treat distillery spent wash at 8d hydraulic retention time with organic loading rate of 23.25 kg COD m(-3)d(-1) leading to 64% COD reduction with biogas production of 7.2 m3 m(-3)d(-1) having high methane yield without any pretreatment or neutralization of the distillery spent wash. This study indicates fixed film biomethanation of distillery spent wash using coconut coir as the support material appears to be a cost effective and promising technology for mitigating the problems caused by distillery effluent.     

Effect of Organic Residues and Liming Materials on Metal Extraction from a Mining-Contaminated Soil

Incubation tests were used to assess the effectiveness of three different organic residues and three different liming materials, alone or in combination, in the remediation of a mine contaminated soil. The organic residues tested were sewage sludge from a municipal wastewater treatment plant (SS), compost from the organic fraction of unsorted municipal solid waste (MSWC), and garden waste compost (GWC), applied at 100 and 200 Mg ha^{? 1}. The liming materials tested were agriculture limestone (6.4 Mg ha^{? 1}), calcium oxide (3.7 Mg ha^{? 1}), and sugar beet sludge (12.2 Mg ha^{? 1}) from the sugar manufacturing process. The soil and mixtures of soil and amendments were adjusted to 70% of the maximum water holding capacity and incubated for 28 days in a controlled-temperature room at 20°C ± 1°C. At the end of the incubation, samples were analyzed for pH, electrical conductivity, organic matter content, CaCl₂-extractable, and' NH4Ac/HAc+ EDTA–extractable metal fractions (Cu, Zn, and Pb). Correlations among the variables and/or similarities among the treatments were identified by principal component analysis and hierarchical cluster analysis. The amendments tested decreased the CaCl₂-extractable Cu and Zn fractions, considered as mobile metal fractions, to below analytical detectable limits, providing organic matter to the soil with levels between 1% and 2% at the end of the experiment, significantly different relatively to the original soil. pH and electrical conductivity reached high values when using 200 Mg ha^{? 1} SS or 200 Mg ha^{? 1} MSWC, with any of the liming materials tested, making these application rates excessive for this particular situation. Furthermore, the treatments using MSWC increased the NH4Ac/HAc+ EDTA–extractable Cu, Pb, and Zn fractions, considered as mobilizable metal fractions, as did the 200 Mg ha^{? 1} SS for Pb and Zn. Considering the overall results, the compost made from garden waste decreased metal solubility in the soil and increased soil pH and organic matter content, without the addition of large amounts of soluble salts, and without increasing the mobilizable metal content. Of the organic materials tested, this was the only one that can be considered adequate for remediation of the contaminated soil under study, at the application rates tested.     

Growth potential of faecal bacteria in simulated psychrophilic/mesophilic zones during composting of organic waste

Aim: This study investigated the growth potential of Salmonella serotype Typhimurium and faecal indicator organisms in compost materials and the correlation between bacterial growth potential and the physico‐chemical composition of the compost substrate and temperature. Methods and Results: Survival of Salm. Typhimurium, Enterococcus spp. and total coliforms at 14, 24 and 37°C was determined in material of different degrees of maturity collected from composting plants for household waste and manure. All three micro‐organisms showed the potential for growth in the material from active composts (Solvita index 4) but inactivation generally occurred over time in mature compost material (Solvita index 7–8). Conclusions: Salm. Typhimurium had the potential for growth in psychrophilic/mesophilic (P/M) zones of immature compost material and its growth potential correlated negatively with the maturity of the compost and the temperature within the simulated P/M zone. Significance and Impact of the Study: The risk of pathogen regrowth in P/M zones during organic waste composting further emphasizes the importance of good management practices and of avoiding P/M zones in combination with low compost maturity.     

Methane emission potential and increased efficiency of a phytoremediation system bioaugmented with Bacillus firmus XJSL 1-10

Horizontal subsurface flow constructed wetland mesocosms (HSSCW) designed to treat municipal waste water were bioaugmented with Bacillus firmus XJSL 1-10. The efficiencies of the three HSSCW mesocosms (non-vegetated HSSCW, Schoenoplectus validus HSSCW and Bambusa vulgaris HSSCW) were assessed. Bioaugmentation not only enhanced the efficiency of the phytoremediation system but also reduced methane emission from an average of 51.3 mg/m2/d to 21.6 mg/m2/d in Schoenoplectus validus HSSCW and from an average of 1708 mg/m2/d to 1473 mg/m2/d in Bambusa vulgaris HSSCW. Each of the three types of bioaugmented HSSCWs showed higher purification efficiency with respect to the removal of BOD and NH4-N than the non-bioaugmented HSSCWs. The performance enhancement was most significant in bioaugmented Schoenoplectus validus HSSCW mesocosm with 48.8 and 44.8% lower BOD, and NH4-N, respectively than the non-bioaugmented HSSCW.