ECO-AQUACULTURE, SUSTAINABLE DEVELOPMENT AND PUBLIC HEALTH Does residual H 2 O 2 result in inhibitory effect on enhanced anaerobic digestion of sludge pretreated by microwave-H 2 O 2 pretreatment process? Jibao Liu 1 & Ruilai Jia 1 & Yawei Wang 1 & Yuansong Wei 1 & Junya Zhang 1 & Rui Wang 1 & Xing Cai 2 Received: 24 June 2015 /Accepted: 26 October 2015 /Published online: 5 November 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract This study investigated the effects of residual H 2 O 2 on hydrolysis-acidification and methanogenesis stages of an- aerobic digestion after microwave-H 2 O 2 (MW-H 2 O 2 ) pre- treatment of waste activated sludge (WAS). Results showed that high sludge solubilization at 35–45 % was achieved after pretreatment, while large amounts of residual H 2 O 2 remained and refractory compounds were thus generated with high dos- age of H 2 O 2 (0.6 g H 2 O 2 /g total solids (TS), 1.0 g H 2 O 2 /g TS) pretreatment. The residual H 2 O 2 not only inhibited hydrolysis-acidification stage mildly, such as hydrolase activ- ity, but also had acute toxic effect on methanogens, resulting in long lag phase, low methane yield rate, and no increase of cumulative methane production during the 30-day BMP tests. When the low dosage of H 2 O 2 at 0.2 g H 2 O 2 /g TS was used in MW-H 2 O 2 pretreatment, sludge anaerobic digestion was sig- nificantly enhanced. The cumulative methane production in- creased by 29.02 %, but still with a lag phase of 1.0 day. With removing the residual H 2 O 2 by catalase, the initial lag phase of hydrolysis-acidification stage decreased from 1.0 to 0.5 day. Keywords Microwave . Hydrogen peroxide . Sludge . Anaerobic digestion . Inhibition . Enzyme activity Introduction With the extensive operation of wastewater treatment facili- ties, huge amounts of sewage sludge are generated annually. In China, over 6.25 million tons of dry sludge was generated in 2013 and increases with the annual growth rate of 13 % (Yang et al. 2015). However, more than 80 % of dewatered sludge is not treated properly (Liu et al. 2013). According to the Action Plan for Water Pollution Prevention and Control (The State Council of the people’ s Republic of China 2015) issued by the State Council of China in April 2015, the sewage sludge treatment rate will increase to 90 % by 2020 and the existing sludge disposal facilities should be upgraded to fulfill discharge standard by 2017. Sewage sludge treatment and disposal has become an extremely urgent challenge in China. On the other hand, sewage sludge is nutrient and energy-rich material, which can be used as fertilizer, as well as the source for energy recovery. Anaerobic digestion is a common technology for sewage sludge treatment. Biogas from the sewage sludge anaerobic digesters can be used in combined heat and power system for energy recovery. In the USA, about 48 % of total wastewater flow is treated with anaerobic digestion (Shen et al. 2015). In Europe, anaerobic digestion is the most commonly used regarding sludge stabi- lization in the countries such as Spain, UK, Italy, and Finland (Kelessidis and Stasinakis 2012). However, there are still some barriers for the application of sludge anaerobic digestion combined with biogas utilization in wastewater treatment plants (WWTPs). In China, for the little attention paid to sew- age sludge treatment in the past decades, less than 3 % of WWTPs are equipped with sludge anaerobic digestion, and Responsible editor: Angeles Blanco Electronic supplementary material The online version of this article (doi:10.1007/s11356-015-5704-z) contains supplementary material, which is available to authorized users. * Yuansong Wei yswei@rcees.ac.cn 1 State Key Joint Laboratory of Environmental Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 2 Shenyang Academy of Environmental Science, Shenyang 110016, China Environ Sci Pollut Res (2017) 24:9016–9025 DOI 10.1007/s11356-015-5704-z