污水處理外文翻譯--在一個(gè)a2o-mbr反應(yīng)器中實(shí)現(xiàn)污泥的脫氮除磷技術(shù)（英文）

1、Nutrient removal in an A2O-MBR reactor with sludge reductionJ. Rajesh Banu, Do Khac Uan, Ick-Tae Yeom *Department of Civil and Environmental Engineering, SungKyunKwan University, 300, Chunchun-dong, Jangan-gu, Suwon-Si 4

2、40-746, Republic of Koreaa r t i c l e i n f oArticle history:Received 20 July 2008Received in revised form 11 December 2008Accepted 15 December 2008Available online 25 February 2009Keywords:A2O reactorMBRNutrient remova

3、lTMPa b s t r a c tIn the present study, an advanced sewage treatment process has been developed by incorporating excesssludge reduction and phosphorous recovery in an A2O-MBR process. The A2O-MBR reactor was operatedat

4、a flux of 17 LMH over a period of 210 days. The designed flux was increased stepwise over a period oftwo weeks. The reactor was operated at two different MLSS range. Thermo chemical digestion of sludgewas carried out at

5、a fixed pH (11) and temperature (75 ?C) for 25% COD solubilisation. The released phos-phorous was recovered by precipitation process and the organics was sent back to anoxic tank. Thesludge digestion did not have any imp

6、act on COD and TP removal efficiency of the reactor. During the210 days of reactor operation, the MBR maintained relatively constant transmembrane pressure. Theresults based on the study indicated that the proposed proce

7、ss configuration has potential to reducethe excess sludge production as well as it didn’t detoriated the treated water quality.? 2008 Elsevier Ltd. All rights reserved.1. IntroductionExcess sludge reduction and nutrients

8、 removal are the two important problems associated with wastewater treatment plant. MBR process has been known as a process with relatively high de- cay rate and less sludge production due to much longer sludge age in th

9、e reactor (Wen et al., 2004). Sludge production in MBR is re- duced by 28–68%, depending on the sludge age used (Xia et al., 2008). However, minimizing the sludge production by increasing sludge age is limited due to the

10、 potential adverse effect of high MLSS concentrations on membrane (Yoon et al., 2004). This prob- lem can be solved by introducing sludge disintegration technique in MBR (Young et al., 2007). Sludge disintegration techni

11、ques have been reported to enhance the biodegradability of excess sludge (Vlyssides and Karlis, 2004). In overall, the basis for sludge reduc- tion processes is effective combination of the methods for sludge disintegrat

12、ion and biodegradation of treated sludge. Advances in sludge disintegration techniques offer a few promising options including ultrasound (Guo et al., 2008), pulse power (Choi et al., 2006), ozone (Weemaes et al., 2000),

13、 thermal (Kim et al., 2003), alkaline (Li et al., 2008) acid (Kim et al., 2003) and thermo chemical (Vlyssides and Karlis, 2004). Among the various disintegration techniques, thermo chemical was reported to be simple and

14、 cost effective (Weemaes and Verstraete, 1998). In thermal-chemical hydrolysis, alkali sodium hydroxide was found to be the most effective agent in inducing cell lysis (Rocher et al., 1999). Conventionally, the nutrient

15、removal was carried out in an A2O process. It has advantage of achieving, nutrient removal along withorganic compound oxidation in a single sludge configuration using linked reactors in series (Tchobanoglous et al., 2003

16、). The phospho- rous removal happens by subjecting phosphorous accumulating organisms (PAO) bacteria under aerobic and anaerobic conditions (Akin and Ugurlu, 2004). These operating procedures enhance pre- dominance PAO,

17、which are able to uptake phosphorous in excess. During the sludge pretreatment processes the bound phosphorous was solubilised and it increases the phosphorous concentration in the effluent stream (Nishimura, 2001). So,

18、it is necessary to remove the solubilised phosphorus before it enters into main stream. Be- sides, there is a growing demand for the sustainable phosphorous resources in the industrialized world. In many developed coun-

19、tries, researches are currently underway to recover the phospho- rous bound in the sludge’s of enhanced biological phosphorus removal system (EBPR). The released phosphorous can be recov- ered in usable products using ca

20、lcium salts precipitation method. Keeping this fact in mind, in the present study, a new advanced wastewater treatment process is developed by integrating three processes, which are: (a) thermo chemical pretreatment in M

21、BR for excess sludge reduction (b) A2O process for biological nutrient removal (c) P recovery through calcium salt precipitation. The experimental data obtained were then used to evaluate the perfor- mance of this integr

22、ated system.2. Methods2.1. WastewaterThe synthetic domestic wastewater was used as the experimen- tal influent. It was basically composed of a mixed carbon source, macro nutrients (N and P), an alkalinity control (NaHCO3

23、) and a microelement solution. The composition contained (L?1) 210 mg0960-8524/$ - see front matter ? 2008 Elsevier Ltd. All rights reserved.doi:10.1016/j.biortech.2008.12.054* Corresponding author. Tel.: +82 031 299 669

24、9.E-mail addresses: rajeshces@gmail.com (J. Rajesh Banu), yeom@skku.edu(I.-T. Yeom).Bioresource Technology 100 (2009) 3820–3824Contents lists available at ScienceDirectBioresource Technologyjournal homepage: www.elsevier

25、.com/locate/biortechHowever, it has been reported that, in wastewater treatment pro- cesses including disintegration-induced sludge degradation, the effluent water quality is slightly detoriated due to the release of non

26、degradable substances such as soluble microbial products (Ya- sui and Shibata, 1994; Sakai et al., 1997; Yoon et al., 2004). During the study period, sCOD concentration in the aerobic basin of MBR was in the range of 18–

27、38 mg/L and corresponding organic concen- tration in the effluent was varied from 4 to 12 mg/L. From this data it can be concluded that the membrane separation played an important role in providing the excellent and stab

28、le effluent quality. Phosphorus is the primary nutrient responsible for algal bloom and it is necessary to reduce the concentration of phosphorus in treated wastewater to prevent the algal bloom. Fortunately its growth c

29、an be inhibited at the levels of TP well below 1 mg/L (Mer- vat and Logan, 1996). Fig. 2 depicts TP removal efficiency of the A2O-MBR system during the period of study. It is clearly evident from the figure that the TP r

30、emoval efficiency of A/O system was remains unaffected after the introduction of sludge reduction. However working on sludge reduction practice such as ozonation on activated sludge ‘‘Nishimura, 2001” has observed that t

31、he solu- bilised phosphorous when returned into the system increases phosphorous concentration in the effluent stream. In the present study, the solubilised phosphorous was recovered in the form of calcium phosphate befo

32、re it enters into main stream. So, the possi- bility of phosphorus increase in the effluent due to sludge reduc- tion practices has been eliminated. The influent TP concentration was in the range of 5.5 mg/L. During the

33、first four weeks of opera- tion the TP removal efficiency of the system was not efficient as the TP concentration in the effluent exceeds over 2.5 mg/L. The lower TP removal efficiency during the initial period was due t

34、o the slow growing nature of PAO organisms and other operational factors such as anaerobic condition and internal recycling. After the initial period, the TP removal efficiency in the effluent starts to increase with inc

35、rease in period of operation. TP removal in A2O process is mainly through PAO organisms. These organisms are slow grow- ing in nature and susceptible to various physicochemical factors (Carlos et al., 2008). During the s

36、tudy period TP removal efficiencyof the system remains unaffected and was in the range of 74–82%. From the results it can be concluded that PAO organisms were not affected by thermo chemical pretreatment and TP in the ef

37、fluent was found to be less than 1 mg/L throughout the study period.Fig. 3 presents data on phosphorus profile of the sludge during the thermo chemical digestion. In the process of thermo chemical digestion, the bound ph

38、osphorous in the biosolids was solubilised and released into the solution. The phosphorous solubilisation was found to be in the range of 45–50%. The alkali increases the pH of the digested mixed liquor and was in the ra

39、nge of 9.2–9.8. This high pH range was favorable for phosphorous removal using cal- cium salt. It is known from the literature that low phosphate resid- uals can be obtained with calcium addition at pH values close to pH

40、 9 (Sedlak, 1991). The phosphorous removal in the supernatant was carried out using lime at a mole ratio of 2.1:1. During precip- itation process 90–95% of the solubilised phosphorous was recov- ered from the supernatant

41、. Another advantage of thermo chemical digestion-lime combination is that the added alkali serves as a neutralizing agent to buffer the pH drop due to sludge digestion and nitrification. In EBPR processes, the phosphorou

42、s re- moval is by means of luxury uptake of P in aerobic basin. The re- moved phosphorous gets incorporated inside the biomass and it raises phosphorous percentage of the sludge. At certain period of time this phenomena

43、would decrease phosphorous uptake by microorganisms and it decreases phosphorous removal efficiency. It can be overcome by either wasting the sludge or by side stream removal of phosphorous in the digested sludge. In cas

44、e of run II and III, the first option was minimized due to the sludge reduction practices. The second option was more realistic, but mere increase in the amount of sludge subjected to digestion by increasing the sludge r

45、ecycle Q over 1.5% Q is not economically feasible (Young et al., 2007). So, it was decided to fix the recycle Q (1.5%) and in- crease the amount of biosolids subjected to thermo chemical digestion. This can be achieved b

46、y adjusting MLSS concentration of the system. From the figure it is evident that, at run III the phos- phorous percentage in the mixed liquor was found to be stabilized around 3.5%. Whereas in the case of run II, the TP%

47、 in the sludge01234567817 32 47 62 77 92 107 122 137 152 167 182 197Period (days)Total Phosphorous (mg/L)0102030405060708090100TP removal (%)Influent Effluent TP removal (%)Fig. 2. TP removal profile during the study per

48、iod.10305070901101 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Period (weeks)TP (mg/L) and TP removal (%)0246810TP in sludge (%) and pHTP solubilisation chemical TP removal (%)TP in sludge (%) pH after d