title: [Enhancement of anaerobic digestion of excess sludge by acid-alkali pretreatment].
abstract: In order to enhance the efficiency of anaerobic digestion of excess sludge, acid-alkali pretreatment method was studied. Three different pretreatment methods (alkali alone,acid-alkali, alkali-acid) were compared to investigate their impacts on hydrolysis and acidification of activated sludge. In addition, their influences on methane-producing in subsequent anaerobic digestion process were also studied. The results showed that the soluble chemical oxygen demand (SCOD) of alkaline treatment alone was about 16% higher than the combining of acid and alkali treatment, SCOD concentration increased to 5406.1 mg x L(-1) after 8 d pretreatment. After treated by acid (pH 4.0, 4 d) and alkali (pH 10.0, 4 d), the acetic acid production and its content in short-chain fatty acids (SCFAs) were higher than other pretreatment methods. And the acetic acid production (as COD/VSS) could reach 74.4 mg x g(-1), accounting for 60.5% of SCFAs. After acid-alkali pretreatment, the C: N ratio of the sludge mixed liquor was about 25, and the C: P ratio was between 35-40, which was more favorable than C: N and C: P ratio of alkali alone and alkali-acid to subsequent anaerobic digestion. The control experiments showed that, after acid-alkali pretreatment, anaerobic digestion cumulative methane yield (CH4/VSS(in)) reached to 136.1 mL x g(-1) at 15 d, which was about 2.5-, 1.6-, and 1.7-fold of the blank (unpretreated), alkali alone pretreatment and alkali-acid pretreatment, respectively. After acid-alkali pretreatment for 8 d and anaerobic digestion for 15 d, the removal efficiency of VSS was about 60.9%, and the sludge reduction effect was better than other pretreatments. It is obvious that the acid-alkali pretreatment method was more favorable to anaerobic digestion and sludge reduction.
authors.affiliation: College of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006, China. yuangh716@163.com
authors.forename: Guang-Huan
authors.initials: GH
authors.lastname: Yuan
authors.forename: Xing-Qiu
authors.initials: XQ
authors.lastname: Zhou
authors.forename: Jian-Dong
authors.initials: JD
authors.lastname: Wu
mesh_terms: D000143:Acids / Q000737:chemistry; D000468:Alkalies / Q000737:chemistry; D000693:Anaerobiosis; D057919:Biological Oxygen Demand Analysis / Q000706:statistics & numerical data; D019149:Bioreactors / Q000382:microbiology; D008697:Methane / Q000032:analysis; D012037:Refuse Disposal / Q000379:methods*; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D000143:Acids; D000468:Alkalies; D012722:Sewage; D008697:Methane