Community Structure of Bacteria and Archaea Associated with Geotextile Filters in Anaerobic Bioreactor Landfills

Landfills are an example of an environment that contains highly complex communities of microorganisms. To evaluate the microbial community structure, four stainless steel pilot-scale bioreactor landfills with single- and double-layered geotextile fabric were used. Two reactors (R-1 and R-2) contained municipal solid waste (MSW) and sewage sludge, while the other two reactors (R-3 and R-4) contained only MSW. A single layer of geotextile fabric (R2GT3 and R3GT3) was inserted in the drainage layers of the two reactors (R-2 and R-3), while a double layer of geotextile fabric (R4GT2 and R4GT1) was inserted in one of the reactors (R-4). Scanning electron microscopy demonstrated that biomass developed on the geotextile fabrics after 540 days of bioreactor operation. The metagenomics analyses of the geotextile samples by 16S rRNA gene sequencing indicated that the geotextile bacterial communities were dominated by the phyla Firmicutes, Bacteroidetes, and Thermotogeae, while Proteobacteria were detected as the rarest bacterial phylum in all the geotextile samples. Treponema, Caldicoprobacter, and Clostridium were the most dominant anaerobic and fermentative bacterial genera associated with the geotextile fabric in the bioreactors. Euryarchaeota was the predominant archaean phylum detected in all the geotextile samples. In the archaeal communities, Methanosarcina, and Vadin CA11 were identified as the predominant genera. The diversity of microorganisms in landfill bioreactors is addressed to reveal opportunities for landfill process modifications and associated operational optimization. Thus, this study provides insights into the population dynamics of microorganisms in geotextile fabrics used in bioreactor landfills.

Analyzing the Reuse Potentials of Landfilled Solid Wastes for Farm Water Treatment and Reuse

The increasing solid waste management problems in developing countries necessitated landfill mining to determine the reuse potentials of landfilled solid waste materials. In this study, characterization of landfilled solid waste obtained from a closed landfill site in Malaysia was conducted to ascertain its reuse potentials for biodegradation in wastewater treatment. The results revealed adequate neutral pH, Moisture Content of 34 %, Organic Content of 10.4 % and Bacterial Population in terms of Total Coliform of 8.3 × 105 CFU/100 mL, which are ideal conditions for biodegradation while porosity n of 51%, allow free flow of water during treatment. The SEM showed irregular shapes and pore spaces and a BET surface area of 3.376 m 2 g-1 which enables adsorption of pollutants on its surface, air diffusion and re-aeration. Furthermore, the waste material was used as media for biodegradation in a lab-scale bioreactor at a hydraulic loading of 4 L m-3 d-1 and inflow rate of 0.1 L min-1. The results showed maximum removal rates of 95, 97, 86, 70, 70, and 98% for COD, BOD, TSS, TDS, NH3-N, and TP respectively. Utilization of this technology as bioreactor landfills will solve landfill congestion and also provide cheap wastewater treatment option.

Numerical Model of Leachate Recirculation in Bioreactor Landfills with High Kitchen Waste Content

Surface spraying, horizontal trenches, and vertical wells are the most common leachate recirculation system used at landfills in engineering practice. In order to quantify the efficiency of the three aforementioned recirculation systems, a hydro–biochem–mechanical-coupled model was developed in the present work, which can describe hydrodynamic and biochemical behaviors in food-waste-rich landfills. A typical landfill cell was modeled in COMSOL. The results indicate that leachate recirculation can accelerate the decomposition of municipal solid waste (MSW) with food-rich waste content, relieving acidification, improving gas generation efficiency, and consequently, increasing the early settlement in landfills.

Stabilization of paper waste in bioreactor landfills using soybean peroxidase enzyme

One obvious way to reduce the amount of paper waste being discarded, and to conserve the forest resources, is to recycle more of the waste paper. But most common waste management technique for solid waste is the use of landfills. This study was aimed at decomposing the waste in aerobic condition before the anaerobic condition using soybean peroxidase enzyme (SBP). One bioreactor cell without enzyme was compared with two bioreactor cells, which contained different concentration of soybean peroxidase enzyme with hydrogen peroxide (H₂O₂). The rate of reaction was analyzed by performing COD, BOD₅, NH₃, TS and pH tests as well as monitoring the settlement. The findings showed that the bioreactors with enzyme had faster decomposition rate than the control one. Final COD concentration in control one was 62.6% higher than the bioreactor having higher concentrations of enzyme. Similarly, final BOD₅ concentration in control one was 70.7% higher than the bioreactor having higher concentration of enzyme. Furthermore, the results were compared with the previous study, the bioreactors having municipal solid waste (MSW) with biosolids. The results showed that the strength of leachate quality was much better in bioreactors having paper waste with enzyme than the bioreactor having MSW with biosolids. The COD reduction rate in case of enzyme was about more than double than the bioreactor having biosolids. Similarly, BOD₅ reduction rate in case of enzyme was 1.6 times higher than the biosolids and TS reduction rate was about 1.4 times higher than the bioreactor having biosolids.

Treatment of leachate generated from bioreactor landfills

Leachate generated from Municipal landfill sites is usually contaminated with organic compounds as well as inorganic pollutants. Leachate needs treatment before being entered to any receiving water body. It is desirable that the leachate should be treated on-site efficiently and cost effectively, particularly for small and remote landfills. The existing processes used for the treatment of leachate often exhibit problems related to treatment time, size, and cost. This study focuses on the development of a low cost treatment method to resolve the existing problems related to on-site leachate treatment and handling. The developed method involved the treatment of given leachate in an anaerobic lagoon with Fenton's reagents followed by aerobic lagoon. The leachate used for the treatment was generated from four solid waste bioreactor landfill models (anaerobic and aerobic) that have high moisture content and high organic concentration of solid waste. The effect of pH control and the different concentrations of Ferrous Sulphate (FeSO₄) and Hydrogen peroxide (H₂O₂) on anaerobic and aerobic lagoons performance were examined in the treatment process. It has been observed that the Fenton's reagents with the ratio of 1:1 have a great influence on COD reduction. The maximum COD reductions with pH in the ranges of 6-7 and 3-4 along with Fenton's reagents have been observed to be 6% (39130 mg/l to 36450 mg/l) and 32% (39130 mg/l to 26430 mg/l) respectively. The overall COD concentration reduction using the proposed treatment was observed to be 50% during the whole treatment process.

Decomposition of High Organic and Moisture Content Municipal Solid Waste in Bioreactor Landfills

With the increase in waste recycling, municipal solid waste (MSW) with high organic and moisture contents are found in various landfills worldwide. If this kind of waste were put into anaerobic condition directly, the pH values will decrease sharply, which will seriously affect the biodegradation of the wastes. This study is aimed to investigate the decomposition of the type of MSW in aerobic condition before the anaerobic biodegradation. In the study, the effects of air addition and biosolids addition on the biodegradation of MSW with high organic and moisture contents were examined. Moreover, the flushing technology was compared with the leachate recirculation technology. Six simulated bioreactor landfills were set up. After about 100 days' operation, it was observed that (1) the mass reduction rate in the aerobic-anaerobic bioreactor was approximately five times of that in the anaerobic bioreactor, the leachate quality was much better than that in the anaerobic bioreactor based on the final COD, BOD 5, TS, and NH 3 concentrations. (2) biosolids have strong buffering effects and the addition of biosolids accelerated the anaerobic biodegradation progress to a great extent. Therefore, it was concluded that initially degrading MSW under aerobic condition before anaerobic degradation with biosolids addition is the optimum strategy for the decomposition of MSW with high organic and moisture contents.

Stabilization of paper waste in bioreactor landfills using soybean peroxidase enzyme

One obvious way to reduce the amount of paper waste being discarded, and to conserve the forest resources, is to recycle more of the waste paper. But most common waste management technique for solid waste is the use of landfills. This study was aimed at decomposing the waste in aerobic condition before the anaerobic condition using soybean peroxidase enzyme (SBP). One bioreactor cell without enzyme was compared with two bioreactor cells, which contained different concentration of soybean peroxidase enzyme with hydrogen peroxide (H₂O₂). The rate of reaction was analyzed by performing COD, BOD₅, NH₃, TS and pH tests as well as monitoring the settlement. The findings showed that the bioreactors with enzyme had faster decomposition rate than the control one. Final COD concentration in control one was 62.6% higher than the bioreactor having higher concentrations of enzyme. Similarly, final BOD₅ concentration in control one was 70.7% higher than the bioreactor having higher concentration of enzyme. Furthermore, the results were compared with the previous study, the bioreactors having municipal solid waste (MSW) with biosolids. The results showed that the strength of leachate quality was much better in bioreactors having paper waste with enzyme than the bioreactor having MSW with biosolids. The COD reduction rate in case of enzyme was about more than double than the bioreactor having biosolids. Similarly, BOD₅ reduction rate in case of enzyme was 1.6 times higher than the biosolids and TS reduction rate was about 1.4 times higher than the bioreactor having biosolids.