title: Alkaline fermentation of waste activated sludge stimulated by saponin: volatile fatty acid production, mechanisms and pilot-scale application.
abstract: Volatile fatty acid (VFA) production stimulated by saponin (SP), an environmentally friendly bio-surfactant, was investigated during sludge alkaline fermentation in laboratory studies and pilot applications. The combined use of SP and pH 9 condition significantly enhanced VFA production to approximately 425 mg COD/g VSS, which was 4.7-fold of raw sludge and 1.5-fold of sole pH 10 adjustment (the optimum pH for alkaline fermentation). Further results indicated that SP & pH 9 condition provided sufficient substrates for acidification and decreased the consumption of VFAs through methanogenesis. Moreover, SP accompanied by moderate alkaline condition (i.e. pH 9) showed weaker inhibitory effects on key enzyme activities and metabolic potential of acidification microorganisms than sole pH 10 adjustment. On this basis, a pilot-scale system involving anaerobic fermentation and anaerobic-anoxic-aerobic step-feed bioreaction tanks was established to study the potential of VFAs as supplementary carbon sources for wastewater treatment. The influent of the pilot system was sanitary wastewater characterized by low C/N ratios from a scenic rural area. After flocculation and nutrient precipitation, the fermentation supernatant was mixed with the influent at a volume ratio of 1:30. With this approach, nitrogen and phosphorus concentrations in effluent fulfilled the first-A wastewater discharge standard in China.
authors.affiliation: College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Ministry of Education Key Laboratory of Yangtze River Water Environment, Collaborative Innovation Center of Advanced Technology and Equipment for Water Pollution Control, Collaborative Innovation Center for Regional Environmental Quality, Tongji University, Room 101, Mingjing Building, 1239 Siping Road, Shanghai 200092, China E-mail: liujia@tongji.edu.cn.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Huang
authors.affiliation: College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Ministry of Education Key Laboratory of Yangtze River Water Environment, Collaborative Innovation Center of Advanced Technology and Equipment for Water Pollution Control, Collaborative Innovation Center for Regional Environmental Quality, Tongji University, Room 101, Mingjing Building, 1239 Siping Road, Shanghai 200092, China E-mail: liujia@tongji.edu.cn.
authors.forename: Tianshuai
authors.initials: T
authors.lastname: Mu
authors.affiliation: College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Ministry of Education Key Laboratory of Yangtze River Water Environment, Collaborative Innovation Center of Advanced Technology and Equipment for Water Pollution Control, Collaborative Innovation Center for Regional Environmental Quality, Tongji University, Room 101, Mingjing Building, 1239 Siping Road, Shanghai 200092, China E-mail: liujia@tongji.edu.cn.
authors.forename: Changming
authors.initials: C
authors.lastname: Shen
authors.affiliation: College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Ministry of Education Key Laboratory of Yangtze River Water Environment, Collaborative Innovation Center of Advanced Technology and Equipment for Water Pollution Control, Collaborative Innovation Center for Regional Environmental Quality, Tongji University, Room 101, Mingjing Building, 1239 Siping Road, Shanghai 200092, China E-mail: liujia@tongji.edu.cn.
authors.forename: Lijun
authors.initials: L
authors.lastname: Lu
authors.affiliation: College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Ministry of Education Key Laboratory of Yangtze River Water Environment, Collaborative Innovation Center of Advanced Technology and Equipment for Water Pollution Control, Collaborative Innovation Center for Regional Environmental Quality, Tongji University, Room 101, Mingjing Building, 1239 Siping Road, Shanghai 200092, China E-mail: liujia@tongji.edu.cn.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
mesh_terms: D019149:Bioreactors; D002244:Carbon / Q000378:metabolism; D002681:China; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000378:metabolism; D010758:Phosphorus; D010865:Pilot Projects; D012503:Saponins / Q000378:metabolism*; D012722:Sewage; D018505:Waste Management / Q000379:methods*; D062065:Wastewater
chemical_list: D002244:Carbon; D005232:Fatty Acids, Volatile; D009584:Nitrogen; D010758:Phosphorus; D012503:Saponins; D012722:Sewage; D062065:Wastewater