Haiyan Guo

Microalgae cultivation using an aquaculture wastewater as growth medium for biomass and biofuel production

Microalgae as a main feedstock has attracted much attention in recent years but is still not economically feasible due to high algal culture cost. The objective of this study was to develop a comprehensive eco-friendly technology for cultivating microalgae Platymonas subcordiformis using aquaculture wastewater as growth medium for biomass and biofuel production. Platymonas subcordiformis was grown in pretreated flounder aquaculture wastewaters taken from different stages. Each of wastewater contained different levels of nutrients. The biomass yield of microalgae and associated nitrogen and phosphorous removal were investigated. The results showed that algal cell density increased 8.9 times than the initial level. Platymonas subcordiformis removed nitrogen and phosphorus from wastewater with an average removal efficiency of 87%-95% for nitrogen and 98%-99% for phosphorus. It was feasible to couple the removal of nitrogen and phosphorus from wastewater to algal biomass and biofuel production. However, further studies are required to make this technologies economically viable for algae biofuel production.

Characteristics of nitrogen and phosphorus removal in a sequencing batch reactor

Laboratory scale experiments were conducted to study the characteristics of N and P removal under different influent organic carbon concentration in a sequencing batch reactor (SBR) with simple anaerobic/aerobic operating mode. Experimental results indicated that, under the operating condition of influent N concentration of 89 mg/L and P concentration of 15 mg/L, when the influent C/N ratio increased from 1.5 to 6.9 (influent C/P ratio from 9 to 41), total N and P removal efficiency improved from 50% and 46% to 78% and 96% respectively. Track studies of N, P and other operating parameters demonstrated that N removal of the SBR was realized through simultaneous nitrification and denitrification (SND) in the aeration phase and anoxic denitrificaiton in the filling phase, P removal was accomplished through conventional anaerobic P release and aerobic P taken-up process. Keeping dissolved oxygen (DO) concentration during the first two aeration hours as low as 0.1-0.6 mg/L is essential for the simultaneous occurrences of nitrification, denitrification and P-taken up.

Study on Treatment of Slaughterhouse Wastewater with Co-Coagulation Flotation and SBR Process

In this paper, the treatments of slaughterhouse wastewater with co-coagulation air-flotation and SRB process was studied. After co-coagulation flotation process, most COD of the influent was reduced and the biodegradability of wastewater was improved, the effluent COD concentration were in the range of 500 to 600 mg/L, NH 4 + -N concentration was about 70 mg/L. After the treatment of SBR, the effluent COD and NH 4 + -N concentration of SBR were further reduced to 65.8 and 13.3 mg/L, averaged COD, NH 4 + -N and SS removal efficiency attained to 80%, 90% and 60% respectively. Such effluent quality reached the national emission standard I (GB18918-2002).

Influence of Influent C/N Ratio and Aeration Rate on the Nitrogen Removal in an Airlift Combined Biofilm Reactor (ACBR)

A novel airlift combined biofilm reactor (ACBR) used for wastewater nitrogen removal was developed and the influence of influent C/N ratio and aeration rate on nitrification and denitrification was studied. The experimental results indicated that nitrifying efficiency declined with the increased influent C/N ratio. Increasing the aeration rate could improve the DO concentration in the aerobic zone and buffering zone and decrease the impact of organic carbon oxidization on nitrification. About 95% of COD and 80% of nitrogen removal were achieved when the influent C/N ratio was 2.7~5.3 and constant influent nitrogen loading rate 0.01 kgN/(m3.d).

Influence of Organic Loading on the Performance and Microbial Structure of the Airlift Combined Biofilm Reactor (ACBR)

A novel airlift combined biofilm reactor (ACBR) was developed and the influence of influent organic loading rate on the removal performance and microbial structure was studied. The experimental results indicated 80% nitrogen removal was achieved in the ACBR reactor under the influent organic loading of 0.28-0.53 kgCOD/(m 3 .d), when the organic loading was further increased, nitrification turned to the limiting step of nitrogen removal. Batch experiments and substrates distribution in the reactor indicated that the reactor was successfully stratified and nitrification and denitrification were mainly accomplished in the aerobic zone and anoxic zone. FISH experiments revealed that beta-subclass was one of the predominant group of bacteria within the biofilm community, Nitrosospira and Nitrospira were the main ammonia oxidizer and nitrite oxidizer respectively. The decreased nitrifier with the enhanced influent organic loading resulted in the deterioration of nitrification effect of the reactor.