Shi Wenxin

Contaminants removal characteristics between floc sludge and aerobic granular sludge in domestic sewage treatment at low temperature

Low temperature may result in low metabolic capability of microorganisms in the treatment units, and then cause the lower removal efficiency for contaminants removal. Therefore, the treatment of domestic sewage at 6°C was studied between floc sludge and aerobic granular sludge. Due to the compact interior structure of aerobic granular sludge, it can provide a proper temperature and dissolved oxygen (DO) for denitrifying bacteria and phosphorus accumulating organisms (PAOs), consequently, the NH4+-N and TN removal efficiency were higher than those of floc sludge, which were 81.06% and 68.31%. Except chemical phosphorus removal by extracellular polymeric substances (EPS), biological phosphorus removal ability of aerobic granular sludge also increased, however, TP removal efficiency was only 32.50%. The temperature dependency of nitrification, denitrification and phosphorus removal were lower for aerobic granular sludge than usually found for floc sludge. However, the activity of phosphorus accumulating organisms (PAOs) was low at 6°C, which indicates PAOs may not be fit for in such circumstance. Aerobic granular sludge technique exhibits outstanding advantages in treating domestic sewage at low temperature, exploring psychrotrophs and rapid cultivating aerobic granular sludge may make the trend for pollution control to face the challenges between the resource crisis and eutrophication.

Effect of Continuous Direct Recycling of Combined Residual Streams on Water Quality at the Pilot Scale in Different Seasons

AbstractThe overall objective of this study is to conduct pilot-scale experiments to examine the effects of the direct continuous recycling of combined residual streams (CRS) of clarifier sludge (C...

Selection of drinking water treatment process to effectively remove precursors of disinfection byproducts

Dissolved organic matter (DOM) in drinking water sources is the main precursors of disinfection by-products (DBPs). To control the formation of DPBs, most of the dissolved organic matter should be removed during the drinking water treatment process. The removal rates of DOM in different water treatment processes are quite different based on the molecular weight distribution of DOM. To understand how DOM will be removed in different treatment processes and further affects the formation of the DPBs, five kinds of water treatment processes, which includes conventional process, pre-oxidation by O3 or KMnO4, and advanced treatment by O3 - granular activated carbon, are designed and applied in this study. Disinfection by-products formation potential (DPBFP) of the treated water by different treatment processes were detected by gas chromatography. Results show that the treatment process combined pre-O3, conventional process and O3-GAC is the optimum combination to remove precursors of disinfection by-products. More than 71% of trihalomethanes and haloacetic acids can be removed by this kind of combined treatment process.

Control of halogenated disinfection by-products precursors by different drinking water treatment process

To control the halogenated disinfection by-products (DBPs), this study analysed the the removal efficiency of DBPFP in pretreatment process, conventional process, advanced process and disinfection process of water supply treatment respectively. The results showed that ozone and potassium permanganate have certain removal efficiency for DBPFP, which could improve the coagulation at the same time, consequently strengthened the sequential removal efficiency of DBPFP by conventional process; Advanced treatment process have relatively higher removal efficiency of THMFP and HAA5FP, which will be further improved by the pretreatment. Compared with the conventional treatment process, the THMs and HAA5 produced by pre-O3+convention+O3-GAC reduced by more than 56% and 73% respectively. While they were 70% and 45% compared to the free chlorine disinfection technology.