Yaobo Fan

MINIMIZATION OF EXCESS SLUDGE PRODUCTION FOR BIOLOGICAL WASTEWATER TREATMENT

Excess sludge treatment and disposal currently represents a rising challenge for wastewater treatment plants (WWTPs) due to economic, environmental and regulation factors. There is therefore considerable impetus to explore and develop strategies and technologies for reducing excess sludge production in biological wastewater treatment processes. This paper reviews current strategies for reducing sludge production based on these mechanisms: lysis-cryptic growth, uncoupling metabolism, maintenance metabolism, and predation on bacteria. The strategies for sludge reduction should be evaluated and chosen for practical application using costs analysis and assessment of environmental impact. High costs still limit technologies of sludge ozonation-cryptic growth and membrane bioreactor from spreading application in full-scale WWTPs. Bioacclimation and harmful to environment are major bottlenecks for chemical uncoupler in practical application. Sludge reduction induced by oligochaetes may present a cost-effective way for WWTPs if unstable worm growth is solved. Employing any strategy for reducing sludge production may have an impact on microbial community in biological wastewater treatment processes. This impact may influence the sludge characteristics and the quality of effluent.

Composting and compost application in China

The current situation of municipal solid waste (MSW) and sewage sludge production (in terms of volume as well as composition) in China is introduced. Composting and compost application in China are reviewed. In China, the production of municipal solid waste and sewage sludge is changing rapidly along with economic development. Composting is mainly applied for treating MSW, about 20% of the total amount of MSW being disposed. MSW composting is mainly co-composted with night soil or sewage sludge. Compost is used in agriculture, forestry and horticulture. Compost application is the key factor influencing the composting development in China. To promote composting and compost application in China, a state-wide survey on the production, composition and physical and chemical properties of MSW and sewage sludge should be carried out. More effort should be made to develop low cost and high efficient composting technologies according to Chinas conditions. The environmental impact of compost application should also be given more attention.

Sewage treatment by a low energy membrane bioreactor.

A new membrane bioreactor (MBR) was developed for treatment of municipal wastewater. The MBR was mainly made up of an activated sludge reactor and a transverse flow membrane module, with an innovative configuration being in application between them. As a result, the transverse flow membrane module and low recirculation flow rate created advantages, such as lower energy consumption and more resistance to membrane fouling. The total energy consumption in the whole system was tested as 1.97+/-0.74 kWh/m(3) (permeate) while using periodical backwash with treated water and backflush with mixed liquor daily, being in the same level as a submerged membrane bioreactor, reported to be 2.4 kWh/m(3) (permeate). Energy consumption analysis in the system shows that the membrane module was more energy consuming than the other four parts listed as pump, aeration, pipe system and return sludge velocity lose, which consumed 37.66-52.20% of the total energy. The effluent from this system could be considered as qualified for greywater reuse in China, showing its potential application in the future.

A cost analysis of sewage sludge composting for small and mid-scale municipal wastewater treatment plants

Abstract The costs of building and operating windrow, aerated static pile (ASP), and horizontal agitated solids bed (HASB) sewage sludge composting facilities for small and mid-scale municipal wastewater treatment plants are analyzed. The capital costs and total annual costs of the composting facilities analyzed range from US

Optimization of MBR hydrodynamics for cake layer fouling control through CFD simulation and RSM design

164 200 to US

Study of a membrane bioreactor with glass fiber flat grille modules and the modules' optimization based on the local critical flux theory.

349 000 and from US

CFD simulation and optimization of membrane scouring and nitrogen removal for an airlift external circulation membrane bioreactor

100 000 to US

Modifying glass fiber surface with grafting acrylamide by UV-grafting copolymerization for preparation of glass fiber reinforced PVDF composite membrane

295 700, respectively. On a per-input-dry-Mg basis, composting costs range from US

Preparation and characterization of PVDF-glass fiber composite membrane reinforced by interfacial UV-grafting copolymerization.

55.31 to US

Influence of carbon sources on nutrient removal in A(2)/O-MBRs: Availability assessment of internal carbon source.

173.66/dry Mg handled depending on the type of system and the moisture content of sewage sludge. Moisture content of sewage sludge is the key factor of capital costs and operating costs for different composting facilities. The lower the moisture content of sewage sludge, the less the capital and operating costs for different composting facilities. A windrow composting facility is cheaper to build and operate than ASP and HASB composting facilities. The dominant components of capital costs for windrow are land acquisition and surfacing, and that for ASP and HASB is equipment. Bulking agents and labor are the key factors of operating costs for sludge composting facilities. The availability of land and the costs of bulking agent will significantly limit the spreading of windrow system in small and mid-scale municipal wastewater treatment plants; however, it is suitable for spreading ASP and HASB sewage sludge composting systems for small and mid-scale municipal wastewater treatment plants in China.