Capability of pulse cycle corridor anaerobic reactor treating composted algae water

As a typical high organic concentration wastewater, composted algae water from the Taihu Lake could be treated with anaerobic biological treatment technology for clean energy biogas. During this process, Cyanobacteria are easy to float and crust in the reactor, thus affecting the efficiency of the gas production and reducing the processing effect of the reactor. Therefore, the design of an efficient anaerobic reactor suitable to the characteristics of cyanobacteria was the main task of the study.We designed a new type of anaerobic reactor, the pulse cycle corridor anaerobic reactor, and considered the performance of processing composted algae water from the Taihu Lake. Simultaneously, sequencing batch experiments on the methanation dynamics of the enriched granular sludge through the stable operation of the reactor was adopted to provide theoretical support on further promotion of treating cyanobacteria. Main contents and results were as follows:With an inoculated aerobic activated sludge from municipal sewage treatment plant, the reactor started up at chemical oxygen demand (COD) concentration of 2000 mg/L, hydraulic retention time (HRT) of 5 d and temperature of (30-35)℃ for 30 d; the pulse cycle corridor anaerobic reactor achieved a stable state. The COD removal efficiency was above 60%, and biogas productivities of unit volume was 0.08 L/(L•d) at this level. When volumetric loading rate increased stage by stage from 0.8 kg/(m3•d) to 3.5 kg/(m3•d), the reactor could perform steadily with a COD removal efficiency as high as 80%. Meanwhile, biogas productivities of unit volume was 1.2 L/(L•d). The reactor had some advantages of quick start-up speed, tending to forming the particulate the sludge and enduring pulse load by shortening the pulse time, increasing the number of cycle of cyanobacteria in the reactor, extending the flowing time of cyanobacteria in the reactor channel, overcoming the phenomenon of cyanobacteria floating, and raising the probability of contact between the cyanobacteria and the sludge.The removal rate of microcystins (TMC-LR, EMC-LR) was over 90%, which indicated that the reactor had a good removal effect on microcystins of the composted cyanobacteria. The main reason for microcystins removal was the effective intercept of cyanobacteria by a large number of cultivated anaerobic granular sludge and the enrichment of numerous indigenous bacteria in the reactor.The methanation kinetics of composted algae water substrated with the granular sludge from the pulse cycle corridor anaerobic reactor was investigated. The maximum specific degradation rate, half saturation constant, and yield coefficient were 1.253 mg/(mg•d), 11 770 mg/L, and 0.256 mL /mg, respectively. Observed by a scanning electron microscope (SEM), the granular sludge was found in the stabilization stage with coupled growing micro-organisms, including methanosarcina, filamentous bacteria, and rod-shaped bacteria. Proteinase, coenzyme F420 and TTC-dehydrogenase activity of granular sludge from pulse cycle corridor anaerobic reactor had been in high level during the duration of the experiment.Results indicated that the pulse cycle corridor anaerobic reactor could effectively deal with the algae-laden water from the Taihu Lake. It provided important value for the biogas fermentation of algae.