Simulation of a membrane bioreactor pilot treating old landfill leachates with activated sludge model no. 1 and no. 3

Dynamic modeling of a full-scale membrane bioreactor performance for landfill leachate treatment

Leachate treatment is crucial in landfill management. As landfill ages, inert constituents and ammonia nitrogen concentration in leachate increases, which results in a decrease in biological treatability. In this study, a full-scale MBR treating leachate was dynamically modeled using ASM1. The investigated landfill has been serving for more than 25 years; thus, a decrease in biodegradable organic content and an increase in nitrogen content of the leachate is expected in the years ahead. The calibrated model predicted MLSS, effluent COD, and effluent TN concentrations with high accuracy. Following the calibration study, it was found that soluble inert COD and soluble inert organic nitrogen fractions were the primary reasons of high COD and TKN concentrations in the effluent, respectively. The validated model of the full-scale MBR system treating leachate can be a useful tool to understand the limitations of the system. Soluble inert constituents of the leachate that pass through the membrane necessiate additional treatment processes for discharge into surface water bodies.

Exploring dynamic membrane as an alternative for conventional membrane for the treatment of old landfill leachate

This study compares the performance of a lab-scale pre-anoxic and post-aerobic submerged dynamic membrane bioreactor (DMBR) with similar studies on conventional membrane bioreactors (MBRs) for the treatment of old landfill leachate (LFL) while presenting a strategy to achieve stable DMBR operation. The results suggested that DMBR performed similar, or in some cases, better than MBRs. Like conventional MBRs treating LFL, DMBR can also accommodate large variations in operating parameters including influent feed composition and loading rates and thus, it can guarantee long term stable bioreactor operation (total nitrogen removal up to 98%) with acceptable effluent quality (Turbidity < 10 NTU). The results also demonstrated that gradual increment in influent LFL concentration was found to be effective for a stable DMBR operation however, it significantly deteriorated dynamic membrane (DM) filtration performance (p < 10E-7), resulting in higher fouling rate and deteriorated effluent quality. Nonetheless, poor DM performance and higher fouling rate were effectively controlled by using lower mesh porosity (52 μm instead of 200 μm) and increase in DM effective filtration area.

Assessment of dynamic membrane filtration for biological treatment of old landfill leachate

This study investigated the behaviour of dynamic membrane (DM) filtration for the treatment of stabilised landfill leachate in a bench-scale pre-anoxic and aerobic submerged dynamic membrane bioreactor (DMBR). Four meshes with different openings (10, 52, 85 and 200 μm) were tested to support the development of DM. Differences were observed among the meshes in supporting the development of the cake layer constituting the DM. The treatment of landfill leachate had an impact on sludge characteristics resulting in deteriorated filtration performance of the DM. Effluent turbidity was often higher than 100 NTU for larger mesh pore size (85 and 200 μm). Low effluent turbidity was achieved with meshes with 10 and 52 μm (13 ± 2 and 26 ± 4 NTU, respectively) although at membrane fluxes lower than 10 L m^{- 2} h^-1. The bioreactor exhibited a moderate organics removal of 50-60% and an ammonia oxidation between 80 and 90%. Incomplete nitrification was observed due to increased concentrations of free ammonia and free nitrous acid, with nitrite effluent concentrations up to 1062 mgNO₂^--N L^-1. Due to the large presence of refractory organic matter in landfill leachate, denitrification was limited resulting in a total nitrogen removal of approximately 20%.

Pilot aerobic membrane bioreactor and nanofiltration for municipal landfill leachate treatment

The purpose of this article is to evaluate the integration of the air stripping, membrane bioreactor (MBR) and nanofiltration (NF) processes for the treatment of landfill leachate (LFL). Pretreatment by air stripping, without adjustment of pH, removed 65% of N-NH3 present in LFL. After pretreatment, the effluent was treated in MBR obtaining 44% of COD removal, and part of the N-NH3 was converted to nitrite and nitrate, which was later removed in the post-treatment. Nanofiltration was shown to be an effective process to improve the removal of organic compounds, the high toxicity present in LFL and nitrite and nitrate generated in the MBR. The system (air stripping + MBR + nanofiltration) obtained great efficiency of removal in most parameters analyzed, with overall removal of COD, ammonia, color and toxicity approximately 88, 95, 100 and 100%, respectively. By this route, treated landfill leachate may be reused at the landfill as water for dust arrestment and also as earth work on construction sites.

Treatment of nanofiltration concentrates of mature landfill leachate by a coupled process of coagulation and internal micro-electrolysis adding hydrogen peroxide

In this study, a coupled process of coagulation and aerated internal micro-electrolysis (IME) with the in situ addition of hydrogen peroxide (H2O2) was investigated for the treatment of nanofiltration (NF) concentrate from mature landfill leachate. The acceptable operating conditions were determined as follows: initial pH 4, polymeric aluminium chloride dosage of 525 mg-Al2O3/L in the coagulation process, H2O2 dosage of 0.75 mM and an hydraulic retention time of 2 h in an aerated IME reactor. As a result, the removal efficiencies for chemical oxygen demand (COD), total organic carbon, UV254 and colour were 79.2%, 79.6%, 81.8% and 90.8%, respectively. In addition, the ratio of biochemical oxygen demand (BOD5)/COD in the final effluent increased from 0.03 to 0.31, and that of E2/E4 from 12.4 to 38.5, respectively. The results indicate that the combined process is an effective and economical way to remove organic matters and to improve the biodegradability of the NF concentrate. Coagulation process reduces the adverse impact of high-molecular-weight organic matters such as humic acids, on the aerated IME process. A proper addition of H2O2 in the aerated IME can promote the corrosion of solid iron (Fe2+/Fe3+) and cause a likely domino effect in the enhancement of removal efficiencies.

Sensitivity analyses and simulations of a full-scale experimental membrane bioreactor system using the activated sludge model No. 3 (ASM3)

An ASM3-based model was implemented in the numerical software MATHEMATICA where sensitivity analyses and simulations of a membrane bioreactor (MBR) system were carried out. These results were compared with those obtained using the commercial simulator WEST. Predicted values did not show significant variations between both software and simulations showed that the most influential operational conditions were influent flow rate and concentrations and bioreactor volumes. On the other hand, sensitivity analyses were carried out with both software programs for the same five outputs: COD, ammonium and nitrate concentrations in the effluent, total suspended solids concentration and oxygen uptake rate in the aerobic bioreactor. Similar results were in general obtained in both cases and according to these analyses, the most significant inputs over the model predictions were growth and storage heterotrophic biomass yields and decay coefficient. Other parameters related to the hydrolysis process or to the autotrophic biomass also significantly influenced model outputs.

Biomass characterization by dielectric monitoring of viability and oxygen uptake rate measurements in a novel membrane bioreactor

The application of permittivity and oxygen uptake rate (OUR) as biological process control parameters in a wastewater treatment system was evaluated. Experiments were carried out in a novel airlift oxidation ditch membrane bioreactor under different organic loading rates (OLR). Permittivity as representative of activated sludge viability was measured by a capacitive on-line sensor. OUR was also measured as a representative for respirometric activity. Results showed that the biomass concentration increases with OLR and all biomass related measurements and simulators such as MLSS, permittivity, OUR, ASM1 and ASM3 almost follow the same increasing trends. The viability of biomass decreased when the OLR was reduced from 5 to 4 kg COD m(-3)d(-1). During decreasing of OLR, biomass related parameters generally decreased but not in a similar manner. Also, protein concentration in the system during OLR decreasing changed inversely with the activated sludge viability.