Research On The Eutrophication Of The Membrane Landscape Wetlands Complex System In Injury Phase

Scarcity and uneven distribution of water resources are unable to meet the rapidly growing population and the economic development in some countries and regions, and the wholeworld faces the water shortage crisis. The artificial wetlands and MBR wastewater treatment process playing a key role in wastewater reusing, which can alleviate the water crisis and improve the water utilization efficiency.This paper was based on a practical engineering case.The effluent quality indexes were monitored in normal operation and MBR membrane damage period, respectively. During the normal operation stage, the respective TN and TP concentrations are more than 30 mg/L and 1.70 mg/L, while the other water quality indexes meet the standard. During the MBR membrane damage period, the downstream water turns turbid. The algal density and SS values in the detention pond showed a good correlation with each other. According to the principal component analysis, increased TN, TP and nitrate concentrations in the MBR effluent was the main reason for the increased SS in the stream detention pond.Floating plants, benthic animals, filter-feeding silver carp and combination experiment researches were used to solve the eutrophication situation in the detention pond. Under 30%～40% coverage, the Lemna minor L, Hydrocharis dubia (Bl.) Backer, Nymphoides peltatum (Gmel.) O. Kuntze have certain absorption of N and P, and reduced part of CODcr, among which, Hydrocharis dubia (Bl.) Backer worked best, with a CODCr removal rate of up to 14.4%. When the respective densities are 0.9 g/L for Cipangopaludina chinensis Gray and 2.68 g/L for Anodonta woodiana, a combination of the two animals could remove up to 29.0% of SS, and the turbidity was reduced to 13.2 NTU. Hypophthalmichthys molitrix has a better purification effect on eutrophication status. When the density was 25.4-46.7g/m3, the inhibition effect on phytoplankton is obvious. But when the stocking density increased to above 46.7 g/m3, the eutrophication situation didn’t improve. The mixture of Hydrocharis dubia (B1.) Backer, Hypophthalmichthys molitrix, Cipangopaludina chinensis and Gray Anodonta woodiana can extend the purification effect of eutrophication. When the coverage of Hydrocharis dubia (B1.) Backer was 30%-40%, the addition of Hypophthalmichthys molitrix, Cipangopaludina chinensis and Gray Anodonta woodiana, The purification lasted for about six weeks, which was three times longer than other experiments.Finally, it is recommended to improve the MBR membrane cleaning methods; replace the larger drum aeration fan; timely prune, replant and salvage the plants in the creek; add balckfish, floating plants, silver carp, benthic animals and submerged plants to inhibit the algae overgrowth in the retention pond.