Analysis of structure changes of microbial community in medium biofilm by ERIC-PCR fingerprinting

A new technique, with medium biofilms and hydrophytes as main components, with microbes, plankton, hydrophytes and aquatic animals as basic ecological elements, was adopted to deal with eutrophication water in Shanghai. A pilot-scale test was carried on, with influent as 6 m³/d, 7 ponds parallelly connected, and with continuous influent and effluent. Water qualities were analyzed and ERIC-PCR fingerprinting method was used to study the natures of biofilm microbes. The results show that, the device has obvious affection on eutrophication water pollution removal, COD, TN, NH₄⁺ -N and TP removal efficiencies are respectively 20.7% ∼48.5%, 20.1% ∼49.7%, 39.8% ∼ 66.2% and 60.0% ∼ 73.9% higher than those of control experiment. Water plants contribute for N and P absorption and removal, the three ponds with plants have higher TN and TP removal efficiency than the tree ones without hydrophytes, the enhanced TN removal efficiencies are 30.1%, 24.9% and 17.6% respectively. ERIC-PCR fingerprinting indicate that the three ponds with water plants have more similar microbial community structure to each other than no hydrophyte ponds, and that mean pairwise similarity coefficient values are 71.8%, 86.9% and 91.0% respectively on 2nd, 15th and 30th day, and at the same time the population diversity indexes rang from 1.89 to 2.22, 2.17 to 2.43 and 2.28 to 2.68, respectively. The above discussions conclude that the systemic population diversity indexes and structure similarity increase, biofilm microbes have gradually abundant population and stable structure, which are in accord with pollution removal efficiencies.