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• Drawbacks of leachate recirculation in fresh refuse landfill were NH 4 + accumulation. • Combined leachate recirculation and ex-situ SBR was effective to remove nitrogen. • Methanogenesis occurred easily in combined leachate recirculation and ex-situ SBR. We determined the effects of ex situ biological wastewater treatment on landfill stabilization under continuous circulation of leachate. Specifically, the waste composition and nitrogen in the leachate during leachate circulation (LC) alone was compared with that in a nitrified leachate circulation (NLC) system. An ex situ sequencing batch reactor (SBR) was applied in the NLC system to oxidize the ammonium to nitrite or nitrate, which was then circulated to landfill for denitrification to nitrogen gas. The chemical oxygen demand (COD) concentration in the leachate was low by NLC versus LC, because in the NLC system, ammonium was oxidized to nitrite/nitrate in the ex situ SBR, and aerobic decomposition and denitrification occurred simultaneously in the landfill, suggesting that the NLC system significantly improves the waste decomposition rate and accelerates landfill stabilization. Because denitrification in the landfill was activated in the NLC system and nitrite/nitrate was reduced to nitrogen gas, the proportion of nitrogen in the gas was higher compared with LC. LC, combined with an SBR, might have value in removing the nitrogen that is discharged from the leachate and in accelerating landfill stabilization, because landfill waste was used as the carbon source for denitrification. [ABSTRACT FROM AUTHOR]

Leachate recirculation for rapid landfill stabilization can result in the accumulation of high-strength ammonium. An on-site sequencing batch reactor (SBR) was therefore, applied to oxidize the ammonium to nitrite, which was then recirculated to the landfill for denitrification to nitrogen gas. At relatively higher ammonium levels, nitrite accumulated well in the SBR; the nitrite was denitrified stably in the landfill, despite an insufficient biodegradable carbon source in the leachate. As the leachate was recirculated, the methane and carbon dioxide contents produced from the landfill fluctuated, implying that the organic acids and hydrogen produced in the acid production phase acted as the carbon source for denitrification in the landfill. Leachate recirculation combined with ex-situ partial nitrification of the leachate may enhance the biodegradation process by: (a) removing the nitrogen that is contained with the leachate, and (b) accelerating landfill stabilization, because the biodegradation efficiency of landfill waste is increased by supplying sufficient moisture and its byproducts are used as the carbon source for denitrification. In addition, partial nitrification using an SBR has advantages for complete denitrification in the landfill, since the available carbon source is in short supply in aged landfills. [ABSTRACT FROM AUTHOR]

Abstract: Aerobic granules were developed in four identical sequencing batch reactors (SBRs) with synthetic wastewater to compare different strategies for the enhancement of granulation. The SBRs were operated by (a) increasing organic loading rate in R1; (b) reducing settling time in R2; (c) extending starvation period in R3; and (d) increasing shear force in R4. The results showed that four operational strategies were able to enhance aerobic granulation successfully in SBR, but that also showed different effect on the granulation process and characteristics of mature aerobic granules. The rapidest granulation was observed by using short settling time (R2) and the granules had higher extracellular polymeric substance (EPS) than other reactors. Extended starvation period (R3) and high shear force (R4) resulted in longer granulation period and the granules with higher integrity and smaller size. Higher organic loading rate (R1) resulted in the granules with larger size and higher K value. The maximum specific COD removal rates (q max) of the granules in all SBRs were at a similar level (0.13–0.16g COD/h-g VSS) but the granules in R1 and R2 had higher apparent half rate constant (K) of 18 and 16mg/L, than those in R3 and R4 (2.8 and 3.3mg/L). [Copyright &y& Elsevier]

The removal efficiency of sequencing batch reactor (SBR) system with synthetic industrial estate wastewater (SIEWW) containing Ni2+ or Pb2+ was increased with the increase of mixed liquor suspended solids (MLSS). But, the sludge volume index (SVI) of the system was increased up to higher than 100mL/g under MLSS of up to 4000mg/L. Also, the effluent NO3 − was decreased with the increase of MLSS. The heavy metals (Ni2+ or Pb2+), BOD5, COD and TKN removal efficiencies of SBR system with SIEWW containing 5mg/L heavy metal (Ni2+ or Pb2+) under MLSS of 3000mg/L were 83–85%, 96–97%, 95–96% and 83–94%, respectively. The increase of heavy metal (Ni2+ or Pb2+) concentrations of SIEWW from 5 to 50mg/L were not significantly effected to both COD and BOD5 removal efficiencies (they were reduced by only 4–5%), but they were strongly effected to both TKN and heavy metals removal efficiencies (they were reduced by 15 and 20–30%, respectively). Both Ni2+ and Pb2+ could repress the growth of both nitrification and denitrification bacteria. And Ni2+ was more effective than Pb2+ to reduce the heavy metals removal efficiency. The SBR system could be applied to treat the industrial estate wastewater (IEWW) containing both Pb2+ and Ni2+ even the heavy metals concentrations was up to 5mg/L, but the removal efficiency was quite low and excess bio-sludge did not produce. However, the system efficiency could be increased with the increase of BOD5 concentration of the wastewater. The Pb2+, Ni2+, COD, BOD5 and TKN removal efficiencies of the system with IEWW containing 500mg/L BOD5, 5mg/L Ni2+ and 5mg/L Pb2+ under HRT of 3 days were 85.68±0.31%, 87.03±0.21%, 86.0±0.5%, 94.04±0.4% and 90.5±0.9%, respectively. And the effluent SRT, SS and SVI of the system were 44.7±0.6 days, 150±6mg/L and 100mL/g, respectively. [Copyright &y& Elsevier]

Abstract: The application of the Anammox process has been usually focused on the treatment of wastewater with temperatures around 30°C in order to operate under optimum conditions. In this work, the feasibility of the application of the Anammox process at lower temperatures has been tested. First, the short-term effects of temperature on the Anammox biomass were studied using batch tests. An activation energy of 63kJmol−1 was calculated and the maximum activity was found at 35–40°C. Activity tests done at 45°C showed an irreversible loss of the activity due to the biomass lysis. A SBR was operated at different temperatures (from 30 to 15°C) to determine the long-term effects. The system was successfully operated at 18°C but when temperature was decreased to 15°C, nitrite started to accumulate and the system lost its stability. Adaptation of biomass to low temperatures was observed when the specific activities obtained during first batch tests are compared to those obtained during the operation of the SBR. [Copyright &y& Elsevier]

Abstract: Biological treatment system especially, sequencing batch reactor (SBR) system could not be applied to treat the raw electroplating wastewater (EPWW) due to the low organic matter concentration of 10±3mg-BOD5/L and toxic of high cyanide concentration of 23.0±2.2mg-CN/L. However, EPWW could be used as the nitrogen source for the bio-sludge of SBR system. And 10% of EPWW (the final cyanide concentration of 2.3±0.2mg/L) was most suitable to supplement into the wastewater as the nitrogen source. SBR system showed the highest COD, BOD5, TKN and cyanide removal efficiencies of 79±2%, 85±3%, 49.0±2.1% and 97.7±0.7%, respectively with 4-times diluted Thai-rice noodle wastewater (TRNWW) containing 10% EPWW and 138mg/L NH4Cl (BOD5: TN of 100:10) at SRT of 72±13 days (under organic and cyanide loadings of 0.40kg-BOD5/m3 d and 0.0023kg-CN/m3 d, respectively). However, the effluent ammonia was still high of 22.6±0.4mg-N/L while the effluent nitrate and nitrite was only 9.9±0.4 and 1.2±0.9mg-N/L, respectively. And SVI and effluent SS of the system were higher than 95 and 75mg/L, respectively. [Copyright &y& Elsevier]

Two types of operation means “SBR reactor alone (control reactor)” and “adding zeolite powder into SBR reactor (test reactor)” were used to treat municipal wastewater. The test results revealed that zeolite powder addition could improve the activity of the activated sludge. It was investigated the specific oxygen utilization rate (SOUR) of the tested zeolite sludge were about double times that of the control activated sludge, and the nitrification rate and settling property of zeolite-activated sludge were both improved. Due to the combination of zeolite adsorption for NH4 +-N and enhanced simultaneous nitrification and de-nitrification (SND), a higher nitrogen removal was observed in test reactor compared to the control reactor, and the addition of zeolite powder is helpful to inhabit sludge bulking. In addition, through long-term parallel shock load test, it was found that the zeolite powder addition could enhance the ability of activated sludge in resisting the shock load of organics and ammonium. Compared to the control activated sludge, zeolite powder added activated sludge could remove COD, NH4 +-N, TN and TP significantly in a shorter cycle time. At the same operational time period, the test SBR could treat wastewater quantity 1. 22 times that treated in control SBR. [Copyright &y& Elsevier]

Leather tannery effluents are a source of severe environmental impacts. In particular, the unhairing stage, belonging to beamhouse processes, generates a significantly toxic, alkaline wastewater with high concentrations of organic matter, sulphides, suspended solids and salts. The objective of this work was to evaluate the biodegradability and toxicity of diluted unhairing wastewater after being treated by an activated sludge (AS) system. The biomass activity of the AS was also evaluated.The AS system was fed for 180 days with diluted unhairing effluent. The operation strategy increased the organic load rate (OLR) from 0.23 to 2.98 g COD/l per day while the HRT was variable until operation day 113, when the HRT was near 1.1 days. Results show that when the organic load rate was lower than 2 g COD/l per day, the biological oxygen demand (BOD5) efficiency was 99%, whereas the chemical oxygen demand (COD) was around 80%. The reactor operation was stable until 2 g COD/l per day. For higher values, the system was less efficient (COD and BOD5 removal rate lower than 40%) and the relation of food/micro-organisms (F/M) was higher than 0.15.Biomass evaluations through oxygen utilisation coefficients show that the specific oxygen uptake rate (SOUR) decreased from 1.11 to 0.083 g O2/g MLVSS per day, in the same way the endogenous oxygen coefficient decreased from 0.77 to 0.058 per day. The reduction of biomass activity (measured as oxygen respiration) could be attributable to the inorganic compound content (ammonia and chloride) in the unhairing effluent. Also, the bioassays with Daphnia magna and Daphnia pulex showed that with these compounds, only between 24 and 31% of the toxicity of the aerobic-treated effluent can be removed. On the other hand, ultrafiltration (UF) analysis indicated that a COD fraction is recalcitrant to the aerobic treatment, principally those above 10,000 Da (around 55% of total unhairing influent COD). [Copyright &y& Elsevier]