Nitrification in sequencing batch reactors with and without glucose addition at 11°C

Co-Treatment of Landfill Leachate and Liquid Fractions of Anaerobic Digestate in an Industrial-Scale Membrane Bioreactor System

The management of the liquid fraction of digestate produced from the anaerobic digestion of biodegradable municipal solid waste is a difficult affair, as its land application is limited due to high ammonium concentrations and the municipal waste that water treatment plants struggle to treat due to high pollutant loads. The amount of leachate and the pollutant load in the leachate produced by landfills usually decreases with the time, which increases the capacity of landfill leachate treatment plants (LLTPs) to treat additional wastewater. In order to solve the above two challenges, the co-treatment of landfill leachate and the liquid fraction of anaerobic digestate in an industrial-scale LLTP was investigated along with the long-term impacts of the liquid fraction of anaerobic digestate on biocoenosis and its impact on LLTP operational expenses. The co-treatment of landfill leachate and liquid fraction of anaerobic digestate was compared to conventional leachate treatment in an industrial-scale LLTP, which included the use of two parallel lanes (Lane-1 and Lane-2). The average nitrogen removal efficiencies in Lane-1 (co-treatment) were 93.4%, 95%, and 92%, respectively, for C/N ratios of 8.7, 8.9, and 9.4. The average nitrogen removal efficiency in Lane-2 (conventional landfill leachate treatment), meanwhile, was 88%, with a C/N ratio of 6.5. The LLTP’s average chemical oxygen demand (COD) removal efficiencies were 63.5%, 81%, and 78% during phases one, two, and three, respectively. As the volume ratios of the liquid fraction of anaerobic digestate increased, selective oxygen uptake rate experiments demonstrated the dominance of heterotrophic bacteria over ammonium and nitrite-oxidising organisms. The inclusion of the liquid fraction of anaerobic digestate during co-treatment did not cause a significant increase in operational resources, i.e., oxygen, the external carbon source, activated carbon, and energy.

Tuning of activated sludge in winter based on respirogram profiles under standard and site temperatures

Respirograms of activated sludge OUR^T_x and OUR²⁰_x were measured under site (T) and standard (20°C) temperatures, respectively, and the predicted standard temperature respirogram OUR²⁰_x,cal was also calculated using the Arrhenius equation. These respirogram profiles reveal more information than effluent quality. A decrease of OUR²⁰_x is a critical alarm signal for the loss of pollutant removal capacity, and a sudden increase of the predicted value OUR²⁰_x,cal is an alarm signal for the unrecoverable deterioration of biomass. The sign of OUR²⁰_x-OUR²⁰_x,cal can be used for selection of tuning strategies. For example, a negative value of OUR²⁰_x-OUR²⁰_x,cal indicates that doubling biomass is difficult, thus strategies such as extending the reaction time with limited available biomass is preferred. The findings in this study elucidated the respiration profile of activated sludge under changes of temperature and can be effectively used for the stable operation of Wastewater Treatment Plants under cold temperatures and seasonal variations.

Nitrogen removal from slaughterhouse wastewater through partial nitrification followed by denitrification in intermittently aerated sequencing batch reactors at 11 degreeC

This study is aimed to examine the removal of nitrogen from high strength slaughterhouse wastewater at 11 degreeC via partial nitrification followed by denitrification (PND), using the intermittently aerated sequencing batch reactor (IASBR) technology. The slaughterhouse wastewater contained chemical oxygen demand (COD) of 6068 mg/L, total nitrogen (TN) of 571 mg/L, total phosphorus (TP) of 51 mg/L and suspended solids of 1.8 g/L, on average. The laboratory-scale IASBR reactors had a working volume of 8 L and was operated at an average organic loading rate of 0.61 g COD/(L-d). At the cycle duration of 12 h, COD was efficiently removed under three aeration rates of 0.4, 0.6 and 0.8 L air/min. Among the three aeration rates, the optimum aeration rate was 0.6 L air/min with removals of COD, TN, and TP of 98%, 98%, and 96%, respectively. The treated wastewater met the Irish emission standards. The microbial community analysis by fluorescence in situ hybridization shows 12 +/- 0.4% of ammonium oxidizing bacteria, and 7.2 - 0.4% of nitrite oxidizing bacteria in the general bacteria (EUB) in the activated sludge at the aeration rate of 0.6 L air/min, leading to efficient partial nitrification. PND effectively removed nitrogen from slaughterhouse wastewater at 11degreeC, but PND efficiency was dependent on the aeration rate applied. PND efficiencies were up to 75.8%, 70.1% and only 25.4% at the aeration rates of 0.4, 0.6, and 0.8 L air/min.

Bio-augmentation to rapid realize partial nitrification of real sewage

The feasibility of bio-augmentation processes in promoting start-up of partial nitrification of sewage was investigated in this study. Initially, partial nitrification was well-established in an anoxic/oxic reactor treating high-strength ammonia wastewater. Then the influent was replaced by real sewage instantly or gradually. In both cases, nitrite pathway could be maintained for 5-7d. However, it was eventually destroyed due to the inevitable over-aeration. In another strategy, sewage was treated in the adsorption/biodegradation reactor. The nitrite pathway was obviously promoted by addition of the previous activated sludge from high ammonia wastewater treatment. Nitrite accumulation efficiency of sewage was quickly increased from 26% to 86% and maintained at a high level for 2 months. Moreover, the effluent has a favorable ratio of NH(4)(+)/NO(2)(-) for feeding anammox process. The experimental results indicated that appropriate bio-augmentation strategies could significantly improve the build-up partial nitrification of sewage in the pretreatment of anammox.