Powdered activated carbon added biological treatment of pre-treated landfill leachate in a fed-batch reactor

Biological treatment of landfill leachate usually results in low treatment efficiencies because of high chemical oxygen demand (COD), high ammonium-N content and also presence of toxic compounds such as heavy metals. A landfill leachate with high COD content was pre-treated by coagulation-flocculation followed by air stripping of ammonia at pH = 12. Pre-treated leachate was biologically treated in an aeration tank operated in fed-batch mode with and without addition of powdered activated carbon (PAC). PAC at 2 g l^–1 improved COD and ammonium-N removals resulting in nearly 86% COD and 26% NH₄-N removal.     

An investigation into the microbial clogging potential of selected filter media as a result of biodegradation of a high-strength sulphate-rich alkaline leachate

The research examines the potential for bio-clogging in filter packs containing fine sand of the type typically used in extraction wells for pumping leachates containing fine particulate matter, such as cement kiln dust (CKD). Three filter media with different particle sizes were used: 1.7–4.75, 0.35–1.0, and 0.235–0.45 mm. Each sand filter was tested using a leachate recirculating column reactor with a free drainage layer, on top of which was placed the filtration medium which was kept saturated and at a positive hydrostatic head by a 2-l reservoir of leachate. The leachate was collected from a landfill site that had been used for the co-disposal of municipal solid waste (MSW) and CKD. The leachate used was filtered by passing through a Whatman GFA filter paper before being added to the reactors in order to eliminate as far as possible the non-biological clogging which might have resulted from the introduction of particulate matter in the form of CKD. The filters and a control experiment were run under anaerobic conditions at 35 °C. The bio-clogging potential was observed by taking differential manometer readings from manometers located in the drainage and reservoir sections of the reactor. No clogging was detected using the coarser of the filter media, but there was some clogging when a finer filter medium was used. Head space gas analysis indicated that methanogenic activity was inhibited and analysis of the liquid phase indicated that the microbial process responsible for removal of chemical oxygen demand (COD) was principally one of sulphate reduction.     

Behavior of dimethyl phthalate (DMP) in simulated landfill bioreactors with different operation modes

The behavior of dimethyl phthalate (DMP) from municipal solid waste (MSW) in the leachate and refuse of two simulated landfill bioreactors was compared. In one reactor, the leachate was circulated between a landfill and a methanogenic reactor, while the other reactor was operated using direct recirculation of the leachate. The results revealed that the original concentration of DMP in the refuse was approximately 3.3 μg g⁻¹, and the concentration decreased greatly during decomposition of the waste in both reactors. The major loss of DMP from the landfill occurred in an active methanogenic environment in the later period, while the environment was acidic due to a high concentration of chemical oxygen demand (COD), volatile fatty acids (VFA), and contained a large volume of biologically degradable material (BDM) during the early stage. In addition, a high correlation was found between the residual DMP concentrations and the BDM of the refuse in both systems. Circulating the leachate between the landfill and a methanogenic reactor resulted in an increase in the biodegradability of MSW and the degree of waste stabilization. Furthermore, the removal of DMP was enhanced 14% in the landfill that was operated in conjunction with the methanogenic reactor when compared to the landfill in which there was direct leachate recirculation.     

Phytoremediation of landfill leachate waste contaminants through floating bed technique using water hyacinth and water lettuce

Abstract

In the present study, the effectiveness of water hyacinth and water lettuce was tested for the phytoremediation of landfill leachate for the period of 15?days. Fifteen plastic containers were used in experimental setup where aquatic plants were fitted as a floating bed with the help of thermo-pole sheet. It was observed that both plants significantly (p?<?0.05/p?<?0.01/p?<?0.001) reduce the physicochemical parameters pH, TDS, BOD, COD and heavy metals like Zn, Pb, Fe, Cu and Ni from landfill leachate. Maximum reduction in these parameters was obtained at 50% and 75% landfill leachate treatment and their removal rate gradually increased from day 3 to day 15 of the experiment. The maximum removal rate for heavy metals such as for Zn (80–90%), Fe (83–87%) and Pb (76–84%) was attained by Eichhornia crassipes and Pistia stratiotes. Value of bioconcentration and translocation factor was less than 1 which indicates the low transport of heavy metals from roots to the above-ground parts of the plants. Both these plants accumulate heavy metals inside their body without showing much reduction in growth and showing tolerance to all the present metals. Therefore, results obtained from the study suggest that these aquatic plants are suitable candidate for the removal of pollution load from landfill leachate.     

Characteristics of the bioreactor landfill system using an anaerobic-aerobic process for nitrogen removal

A sequential upflow anaerobic sludge blanket (UASB) and air-lift loop sludge blanket (ALSB) treatment was introduced into leachate recirculation to remove organic matter and ammonia from leachate in a lab-scale bioreactor landfill. The results showed that the sequential anaerobic-aerobic process might remove above 90% of COD and near to 100% of NH4+ -N from leachate under the optimum organic loading rate (OLR). The total COD removal efficiency was over 98% as the OLR increased to 6.8-7.7 g/l d, but the effluent COD concentration increased to 2.9-4.8 g/l in the UASB reactor, which inhibited the activity of nitrifying bacteria in the subsequent ALSB reactor. The NO3- -N concentration in recycled leachate reached 270 mg/l after treatment by the sequential anaerobic-aerobic process, but the landfill reactor could efficiently denitrify the nitrate. After 56 days operation, the leachate TN and NH4+ -N concentrations decreased to less than 200 mg/l in the bioreactor landfill system. The COD concentration was about 200 mg/l with less than 8 mg/l BOD in recycled leachate at the late stage. In addition, it was found that nitrate in recycled leachate had a negative effect on waste decomposition.     

The effect of landfill age on municipal leachate composition

The influence of municipal landfill age on temporal changes in municipal leachate quality on the basis of elaboration of 4 years monitoring of leachate from landfill in Wysieka near Bartoszyce (Poland) is presented in this study. In leachate, concentrations of organic compounds (COD, BOD(5)), nutrients (nitrogen, phosphorus), mineral compounds, heavy metals and BTEX were investigated. It was shown that the principal pollutants in leachate were organics and ammonia - as landfill age increased, organics concentration (COD) in leachate decreased from 1,800 mg COD/l in the second year of landfill exploitation to 610 mg COD/l in the sixth year of exploitation and increase of ammonia nitrogen concentration from 98 mg N(NH)/l to 364 mg N(NH4) /l was observed. Fluctuation of other indexes (phosphorus, chlorides, calcium, magnesium, sulfate, dissolved solids, heavy metals, BTEX) depended rather on season of the year (seasonal variations) than landfill age. Moreover, the obtained data indicate that despite of short landfill's lifetime some parameters e.g. high pH (on average 7.84), low COD concentration (<2,000 mg COD/l), low BOD(5)/COD ratio (<0.4) and low heavy metal concentration, indicated that the landfill was characterized by methanogenic conditions already at the beginning of the monitoring period.     

A novel membrane bioreactor enhanced by effective microorganisms for the treatment of domestic wastewater

The activated sludge membrane bioreactor (MBR) has been shown to have some advantages for the processing and reclamation of domestic wastewater. We hypothesized that certain microorganisms, chosen for their abilities to decompose the chemical components of raw sewage, would, when coupled with the MBR, significantly improve the stability and efficiency of this system. We selected environmental bacterial strains which oxidize ammonia and nitrites and produce protease, amylase, and cellulase for the development and testing of a novel biologically enhanced MBR (eMBR). We compared the eMBR with the activated sludge MBR. With the eMBR, the average values of effluent quality were: chemical oxygen demand (COD), 40 mg/l(average efficiency of removal 90.0%); and NH₄ ⁺–N, 0.66 mg/l(average efficiency of removal 99.4%). Effluent qualities met the standard and were stable during the entire 90 days of this study. For the activated sludge MBR, the COD removal rate was 91.7%, and the NH₄ ⁺–N removal (94.8%) was less than that of the eMBR. Start-up time for the eMBR was only 24–48 h, much shorter than the 7–8 days required to initiate function of the standard MBR. The biomass concentrations of total heterotrophic bacteria and autotrophic bacteria in the eMBR did not fluctuate significantly during the course of the study. Various kinds of microorganisms will establish an ecological balance in the reactor. Compared with the activated sludge MBR, the eMBR not only produced an excellent and stable quality of effluent but also resulted in a shorter time to start-up and significantly improved the efficiency of NH₄ ⁺–N removal.     

Colour removal from landfill leachate by coagulation and flocculation processes

A study was conducted to investigate the efficiency of coagulation and flocculation processes for removing colour from a semi-aerobic landfill leachate from one of the landfill sites in Malaysia. Four types of coagulant namely aluminium (III) sulphate (alum), ferric (III) chloride, ferrous (II) sulphate and ferric (III) sulphate were studied using standard jar test apparatus. Results indicated that ferric chloride was superior to the other coagulants and removed 94% of colour at an optimum dose of 800 mg/l at pH 4. The effect of coagulant dosages on colour removal showed similar trend as for COD, turbidity and suspended solids. This suggested that colour in landfill leachate was mainly contributed by organic matters with some insoluble forms that exhibited turbidity and suspended solids readings. The results from this study suggested that ferric chloride could be a viable coagulant in managing colour problems associated with landfill leachate.     

Novel engineering controls to increase leachate contaminant degradation by refuse: From lab test to in situ engineering application

Here we provide direct evidence through a series laboratory and field-scale experiments using different age refuse to treat landfill leachate that aged refuse exhibits increased leachate contaminants removal ability with refuse stabilization time addition. Ten-years aged refuse showed best contaminant removal in a laboratory-scale test, removing 70.0% (8340.0-2540.0 mg/L) chemical oxygen demand (COD) and 75.0% (910.0-215.0 mg/L) ammonium-N, as well as removing 61.5-67.0% COD and 50.4-58.1% ammonium-N with variable COD (9948.0-12286.0 mg/L) and NH₃-N (780.0-1184.0 mg/L) in a field-scale test, respectively. When the 10-years aged refuse was disinfected by 20% NaClO (wt%), COD, biochemical oxygen demand (BOD₅), total nitrogen (TN), and ammonium-N removal showed a dramatic decrease throughout operation time from 84.4-86.2% to 15.2-34.5%, 94.4-99.8% to 26.2-54.4%, 31.2-33.9% to 2.1-10.1%, and 88.5-90.1% to 1.5-14.5%, respectively, suggesting biodegradation is the dominant contaminant removal. Based on this finding, a 3-stages (8 years) age refuse bioreactor (ARB) was constructed to treat leachate and ARB efficiently reduced chemical oxygen demand (COD) from 5478.0-10842.0 mg/L to 261.0-1020 mg/L (87.8-96.2% removal), ammonium-N from 811.4-1582.0 mg/L to 8.5-43.3 mg/L (96.9-99.4%), respectively, in 18 months running. In summary, the present studies suggest that increased leachate contaminant biodegradation ability of aged refuse could be used directly to create an engineering approach to treat leachate with operational and economic advantages.     

异养硝化⁃好氧反硝化复合菌剂在垃圾渗滤液处理中的应用

垃圾渗滤液中往往含有高浓度的有机物、氨氮等污染物。异养硝化-好氧反硝化型微生物能在脱氮的同时去除部分有机物,但目前对于相关混合菌剂直接应用于垃圾渗滤液处理的研究较少。从垃圾渗滤液中筛选出6株异养硝化-好氧反硝化菌株并组配成复合菌剂F6,探究菌剂在垃圾渗滤液中的脱氮效果。分别以单一菌株和复合菌剂F6为投放原料;以不同碳氮比、活性炭浓度、转速以及微量元素浓度为影响因素,研究复合菌剂对于垃圾渗滤液中氨氮(NH{}_{\mathrm{4}}^{+}-N)、总氮(total nitrogen, TN)、化学需氧量(chemical oxygen demand, COD)的去除性能。结果表明,提高碳氮比和微量元素浓度能够促进复合菌剂F6的降解效果;当接种量为10%、碳氮比为15%时,F6对NH{}_{\mathrm{4}}^{+}-N、TN、COD的去除率分别为74.69%、89.23%和83.50%,与不添加活性炭的处理相比,分别提高了约18.46%、20.97%和7.98%。复合异养硝化-好氧反硝化菌剂F6对高氨氮垃圾渗滤液去除NH{}_{\mathrm{4}}^{+}-N、TN、COD等方面具有良好的应用前景。     

Characterization and Phylogenetic Diversity of Carboxymethyl Cellulase Producing <Emphasis Type="Italic">Bacillus</Emphasis> Species from a Landfill Ecosystem

Total population of cellulose degrading bacteria was studied in a landfill ecosystem as a part of microbial diversity study. Samples were obtained from 3 and 5 feet depth of a local landfill being operated for past 10 years. Among many isolates, 22 bacterial strains were selected based on their capability to decompose carboxymethyl cellulose (CMC). These isolates were cultivated on agar medium with CMC as the carbon source. All isolates were Gram positive, endospore forming and alkalophilic bacteria with optimum growth pH 9–10. They were grouped based on the phenotypic and chemotaxonomic characters and representative strains of different groups along with high carboxymethyl cellulase (CMCase) producing strains were included for further characterization. Analysis of 16S rRNA gene indicated that these strains belong to different species of the genus Bacillus. Maximum CMCase activity of 4.8 U/ml at 50°C was obtained by strain LFC15. Results in the present study indicated the potential of waste land ecosystems such as landfill are potential source for isolation of industrially important microorganisms.     

Heterotrophic nitrification–aerobic denitrification by novel isolated bacteria

Three novel strains capable of heterotrophic nitrification–aerobic denitrification were isolated from the landfill leachate treatment system. Based on their phenotypic and phylogenetic characteristics, the isolates were identified as Agrobacterium sp. LAD9, Achromobacter sp. GAD3 and Comamonas sp. GAD4, respectively. Batch tests were carried out to evaluate the growth and the ammonia removal patterns. The maximum growth rates as determined from the growth curve were 0.286, 0.228, and 0.433 h⁻¹ for LAD9, GAD3 and GAD4, respectively. The maximum aerobic nitrification–denitrification rate was achieved by the strain GAD4 of 0.381 mmol/l h, followed by LAD9 of 0.374 mmol/l h and GAD3 of 0.346 mmol/l h. Moreover, hydroxylamine oxidase and periplasmic nitrate reductase were successfully expressed in all the isolates. The relationship between the enzyme activities and the aerobic nitrification–denitrification rates revealed that hydroxylamine oxidation may be the rate-limiting step in the heterotrophic nitrification–aerobic denitrification process. The study results are of great significance to the wastewater treatment systems where simultaneous removal of carbon and nitrogen is desired.     

Removal of sulphate, COD and Cr(VI) in simulated and real wastewater by sulphate reducing bacteria enrichment in small bioreactor and FTIR study

The present study was conducted to investigate the chromium(VI), COD and sulphate removal efficiency from aqueous solution and treatment of real effluent (CETP) in a small scale bioreactor using sulphate reducing bacteria consortium. Effect of different hydraulic retention times (HRTs), initial metal concentrations, various carbon sources and temperatures were studied on removal of chromium(VI), COD and sulphate. Maximum chromium(VI) and sulphate removal was found to be 96.0% and 82.0%, respectively, at initial concentration of 50 mg l⁻¹ using lactate as carbon source. However, highest COD removal was 36.2% in medium containing fructose as the carbon source and electron donor. NADH dependent chromate reductase activity was not observed which indicated the anaerobic consortium. Initially consortium medium with a strong negative oxidation reduction potential indicated the reducing activity. The FTIR spectrum of the sulphate reducing bacteria consortium clearly shows the existence of the sulphate ions and signifies that sulfate reducing bacteria have used sulfate during the growth phase.     

Decolorization of synthetic melanoidins-containing wastewater by a bacterial consortium

The presence of melanoidins in molasses wastewater leads to water pollution both due to its dark brown color and its COD contents. In this study, a bacterial consortium isolated from waterfall sediment was tested for its decolorization. The identification of culturable bacteria by 16S rDNA based approach showed that the consortium composed of Klebsiella oxytoca, Serratia mercescens, Citrobacter sp. and unknown bacterium. In the context of academic study, prevention on the difficulties of providing effluent as well as its variations in compositions, several synthetic media prepared with respect to color and COD contents based on analysis of molasses wastewater, i.e., Viandox sauce (13.5% v/v), caramel (30% w/v), beet molasses wastewater (41.5% v/v) and sugarcane molasses wastewater (20% v/v) were used for decolorization using consortium with color removal 9.5, 1.13, 8.02 and 17.5%, respectively, within 2 days. However, Viandox sauce was retained for further study. The effect of initial pH and Viandox concentration on decolorization and growth of bacterial consortium were further determined. The highest decolorization of 18.3% was achieved at pH 4 after 2 day of incubation. Experiments on fresh or used medium and used or fresh bacterial cells, led to conclusion that the limitation of decolorization was due to nutritional deficiency. The effect of aeration on decolorization was also carried out in 2 L laboratory-scale suspended cell bioreactor. The maximum decolorization was 19.3% with aeration at KLa = 2.5836 h⁻¹ (0.1 vvm).     

Cascade bioreactor with submerged biofilm for aerobic treatment of Tunisian landfill leachate

A bioreactor cascade with a submerged biofilm is proposed to treat young landfill leachate of jbel chakir landfill site south west from capital Tunis, Tunisia. The prototype was run under different organic loading charges varying from 0.6 to 16.3 kg TOC m⁻³ day⁻¹. Without initial pH adjustment total organic carbon (TOC) removal rate varied between 65% and 97%. The total reduction of COD reached 92% at a hydraulic retention time of 36 h. However, the removal of total kjeldahl nitrogen for loading charges of 0.5 kg N m⁻³ day⁻¹ reached 75%. The adjustment of pH to 7.5 improved nitrogen removal to a rate of 85% for loading charge of 1 kg N m⁻³ day⁻¹. The main bacterial groups responsible for a simultaneous removal of organic carbon and nitrogen belonged to Bacillus, Actinomyces, Pseudomonas and Burkholderia genera. These selected isolates showed a great capacity of degradation at different leachate concentrations of total organic carbon.     

Impact of leachate recirculation and recirculation volume on stabilization of municipal solid wastes in simulated anaerobic bioreactors

The effects of leachate recirculation and the recirculation rate on the anaerobic treatment of domestic solid waste was investigated in three simulated landfill anaerobic bioreactors. A single pass reactor was operated without leachate recirculation while the other two reactors were operated with leachate recirculation. The leachate recirculation rate was 9 l/day (13% of the reactor volume) in Reactor₉, while the recirculation rate was 21 l/day (30% of the reactor volume), in Reactor₂₁. pH, chemical oxygen demand (COD), volatile fatty acids (VFA), ammonium–nitrogen (NH₄–N) total and methane gas measurements in leachate samples were regularly monitored. After 220 days of anaerobic incubation, it was observed that the pH, COD, VFA concentrations, methane gas productions and methane percentages in Reactor₉ were better than the single pass reactor and Reactor₂₁. When the leachate recirculation rate was increased to three times a decrease in pH, and an increase in VFA and COD concentrations were observed in Reactor₂₁. The COD values were measured as 47 000, 39 000 and 52 000 mg/l while the VFA concentrations were 15 000, 13 000 and 21 000 mg/l, respectively, in single pass, Reactor₉ and Reactor₂₁ after 220 days of anaerobic incubation. The values of pH were 5.89, 6.44 and 6.16, respectively, after anaerobic incubation. The mean methane percentages of single pass reactor, Reactor₉ and Reactor₂₁ were 30, 50 and 40%, respectively, after 50 days of incubation. Leachate recirculation reduced the waste stabilization time and was effective in enhancing methane gas production and improving leachate. However, leachate recirculation was not effective in removing ammonia from the leachate. The amounts of COD recovered by methane were 62.9, 162.3 and 94.6 g for single pass, Reactor₉ and Reactor₂₁, respectively, at the end of 220 days of anaerobic incubation.     

Reduction of phenolics content and COD in olive oil mill wastewaters by indigenous yeasts and fungi

Olive oil mill wastewaters (OOMW) cause a recurrent environmental pollution problem. The large concentration of phenolic compounds in the organic fraction of OOMW is principally responsible for the phytotoxicity and microbial growth inhibitory effects of the effluent. Candida boidinii, Geotrichum candidum, a Penicillium sp. and Aspergillus niger HA37 were isolated from OOMW. When cultivated directly on an undiluted OOMW-based medium containing 82 g l⁻¹ COD, these strains removed only 4–8% of chemical oxygen demand (COD) and phenolics. In contrast, reduction values attaining respectively 40–73% for phenolics and 45–78% for COD removal in the undiluted OOMW-based medium were obtained when using the strains gradually acclimated to high concentration of OOMW by successive stepwise transfer from media containing COD of 20.5 up to 82 g l⁻¹. Possibly, a sufficient production level of degradation and/or detoxification enzymes has to be attained to overcome the toxic effects of the phenolic fraction of concentrated OOMW. The present investigation calls attention to the necessity of acclimation for certain fungal and yeasts strains potentially useful for treating highly polluted effluents.     

Photoelectrochemical treatment of landfill leachate in a continuous flow reactor

Leachate from a municipal landfill site, which has been treated by biological process, was treated by photoelectrochemical oxidation in a pilot scale flow reactor, using DSA anode and UV light irradiation. At a current density of 67.1 mA/cm² and 2.5 h reaction time, the removal rates achieved were for 74.1% COD, 41.6% for TOC, and 94.5% for ammonium in the electrolysis process with UV light irradiation. In comparison, the removal rates of COD, TOC, and ammonium were decreased in the individual electrolysis process, respectively. The increase induced by the UV light irradiation was analyzed. The removal rates increased with the increase of current densities in the photoelectrochemical process. Combined with UV–vis spectra and gas chromatography–mass spectroscopy analysis, it is believed that the organic contaminants were efficiently mineralized into small molecular acids. At the meantime, the concentrations of metal ions in the landfill leachate were largely reduced.     

Development of a microbial consortium for dairy wastewater treatment

The wastewater from the dairy industries usually contains high concentrations of contaminants and, since the volume generated is also high, the total contaminant load is very significant. Among the available options for treatment, biological degradation looks like the most promising one. Furthermore, the supplementation of the native microbial populations with external microorganisms with high specific degradation rates (bio-augmentation) has demonstrated to improve the performance of treatment. The main objective of this research was to select a combination of bacteria to improve the aerobic treatment of dairy processing wastewater. For this purpose, eleven fat/protein-degrading microorganisms belonging to the genera Bacillus, Serratia, Lactococcus, Enterococcus, Stenotrophomonas, Klebsiella and Escherichia, were evaluated as potential degrading bacteria using a Plackett-Burman design. Assays were carried out to select the strains that most significantly influenced the degradation of wastewater and biomass yield, in terms of COD removal. A simulated dairy industry effluent was used as culture medium. Four strains were selected as potential members of the microbial consortium: Lactococcus garvieae, Bacillus thuringiensis, Escherichia coli and Stenotrophomonas sp. The optimal operation temperature and pH range of the selected consortium were 32°C and 6 ～ 8, respectively. The degradation percentages reached with the selected consortium were 80.67 and 83.44% at 24 and 48 h, respectively. The selected consortium significantly improved the degradation of the dairy wastewater, and the degradation degree achieved by this consortium was higher than by using the strains individually.     

In situ simultaneous organics and nitrogen removal from recycled landfill leachate using an anaerobic-aerobic process

An anaerobic-aerobic process including a fresh refuse landfill reactor as denitrifying reactor, a well-decomposed refuse reactor as methanogenesis reactor and an aerobic activated sludge reactor as nitrifying reactor was operated by leachate recirculation to remove organic and nitrogen simultaneously. The results indicated that denitrification and methanogenesis were carried out successfully in the fresh refuse and well-decomposed landfill reactors, respectively, while the nitrification of NH(4)(+)-N was performed in the aerobic reactor. The maximum organic removal rate was 1.78 kg COD/m(3)d in the well-decomposed refuse landfill reactor while the NH(4)(+)-N removal rate was 0.18 kg NH(4)(+)-N/m(3)d in the aerobic reactor. The biogas from fresh refuse reactors and well-decomposed refuse landfill reactors were consisted of mainly carbon dioxide and methane, respectively. The volume fraction of N(2) increased with the increase of NO(3)(-)-N concentration and decreased with the drop of NO(3)(-)-N concentration. The denitrifying bacteria mustered mainly in middle layer and the denitrifying bacteria population had a good correlation with NO(3)(-)-N concentration.