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Hao X.,Beijing University of Civil Engineering and Architecture | Cai Z.,Beijing University of Civil Engineering and Architecture | Gan Y.,Beijing Drainage Group Co. BDG
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2011

Energy production from excess sludge derived from anaerobic digestion in biological wastewater treatment has been once again emphasized after the Copenhagen summit conference on global climate change. Disruption and/or hydrolysis of bacterial cells is a bottleneck limiting the efficiency of anaerobic digestion, but suitable pretreatment for excess sludge could enhance disruption and/or hydrolysis of bacterial cells and thus greatly enhance the potential green energy available from excess sludge. Today, there are many pretreatment technologies for excess sludge available. Many pretreatment technologies, such as ultrasonic and focused pulsed methods, have already been applied in engineering practice. Moreover, some technologies, such as thermal hydrolysis and alkaline pretreatment, and biological agents added to excess sludge are in research and development. In this article, pretreatment technologies are categorized as physical/mechanical, chemical, biological and combined pretreatment methods, and each method is described in detail including their theories, characteristics, R&D progress and prospects for application.

Zhang L.,Harbin Institute of Technology | Zhang S.,Beijing Drainage Group Co. BDG | Wang S.,Beijing University of Technology | Wu C.,Beijing University of Technology | And 4 more authors.
Chemosphere | Year: 2013

The production of volatile fatty acids (VFAs) from primary sludge and the subsequent application to improve biological nutrient removal has drawn much attention. In this study, a novel approach of using primary sludge as an additional carbon source was conducted in batch tests. The nitritation effluent was directly injected into the sludge fermentation reactor to achieve nitrogen removal. Complete denitrification could be realized in the combined reactor. Moreover, injecting nitrite not only promoted the sludge stabilization process, but also reduced the release of phosphate and ammonium during sludge stabilization. The novel process was further evaluated in a continuous system by treating sludge dewatering liquors. Under optimum conditions, 85% removal of ammonium and 75% of total nitrogen could be obtained using primary sludge, resulting in the suitable effluent for recycling into the inlet of the wastewater treatment plant. © 2013 Elsevier Ltd.

Zhang L.,Harbin Institute of Technology | Liu M.,Beijing Jiaotong University | Zhang S.,Beijing Drainage Group Co. BDG | Yang Y.,Harbin Institute of Technology | And 2 more authors.
Chemosphere | Year: 2015

A pilot-scale activated sludge bioreactor was filled with immobile carrier to treat high ammonium wastewater. Autotrophic nitrogen elimination occurred rapidly by inoculating nitrifying activated sludge and anammox biofilm. As the ammonium loading rate increased, nitrogen removal rate of 1.2kgNm-3d-1 was obtained with the removal efficiency of 80%. Activated sludge diameter distribution profiles presented two peak values, indicating simultaneous existence of flocculent and granular sludge. Red granular sludge was observed in the reactor. Furthermore, the results of morphological and molecular analysis showed that the characteristics of granular sludge were similar to that of biofilm, while much different from the flocculent sludge. It was assumed granular sludge was formed through the continuous growth and detachment of anammox biofilm. The mechanism of granular sludge formation was discussed and the procedure model was proposed. According to the experimental results, the integrated fixed-biofilm activated sludge reactor provided an alternative to nitrogen removal based on anammox. © 2015 Elsevier Ltd.

Zhang L.,Harbin Institute of Technology | Zhang S.,Beijing Drainage Group Co. BDG | Gan Y.,Beijing Drainage Group Co. BDG | Peng Y.,Harbin Institute of Technology | Peng Y.,Beijing University of Technology
Chemosphere | Year: 2012

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 5-7. d. 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 NH4+/NO2- 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. © 2012 Elsevier Ltd.

Zhang L.,Harbin Institute of Technology | Zhang S.J.,Beijing Drainage Group Co. BDG | Zhou J.,Beijing Drainage Group Co. BDG | Wang S.Y.,Beijing Drainage Group Co. BDG | And 3 more authors.
Water Science and Technology | Year: 2010

A novel system was used for nitrogen removal from reject water. This system includes one anoxic/oxic reactor for nitrification and a special reactor for denitrification in which primary sludge was added intermittently as electron donor. In denitrification reactor, sludge fermentation and denitrification reaction took place simultaneously and promoted each other. It was found that effluent recycle could improve nitrogen removal efficiency due to reclaiming of alkalinity. Under steady state conditions, the average solid retention time (SRT) in denitrification reactor was 12-15 d, a total nitrogen loading rate was 0.2 kg N/(m3 day) and TN removal efficiency was more than 90% without extra carbon source addition. Primary sludge was degraded so that volatile suspended solid (VSS) decreased by 50%. Further investigation showed that ORP could be taken as a control parameter for sludge addition. © IWA Publishing 2010.

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