Removal Effect Of Strengthened Ecological Floating Beds On The Nitrogen And Phosphorus Of Urban Sewage

Nowadays,many rivers' water quality is worse than grade V,which seriously affects their ecological health.In order to improve water environment of Luxi River,the ecological water engineering project of which was set the goal that the water quality index of nitrogen and phosphorus of Luxi River should achieve grade ? as the long-term goals.Artificial floating bed is one of the important river restoration technologies that can take into account both ecological landscape and water purification function,but the purification efficiency of traditional floating bed needs to be improved.In this paper,we combined the matrix,animal and combined plant floating bed to establish strengthened floating beds.The water quality of the inferior five types was set as(ammonia nitrogen: 7.50±2.00mg/L,total nitrogen: 8.50±2.00mg/L,total phosphorus: 0.55±0.10 mg/L).The purifying effect and mechanism were investigated experimentally.(1)According to the literature investigation,the plant combinations of floating beds were obtained by combining the purification effect of plants and the screening of local dominant species: Myriophyllum aquaticum-Canna glauca L.-Hydrilla verticillata and cyperus alternifolius-Myriophyllum aquaticum-Hydrilla verticillata.(2)A matrix screening model was established,and the zeolite adsorption performance of green zeolite,vermiculite and gravel were selected.The experimental results show that the performance value of green zeolite is the best matrix for nitrogen and phosphorus adsorption performance,and roseite-green zeolite is the second.After the plants-matrix test,the combination of green zeolite and plants group included canna is the best.(3)Four aquatic animals with universal distribution and strong water purification capacity were selected for adaptation research.Aquatic animals were screened according to the survival rate and dissolved amount of each experimental group.Snails have the strongest adaptability to the water that worse than grade V,and the Hyriopsis cumingii is the second,which are selected for the floating bed test in the inferior five types of the water environment.(4)The CSFB group had the best removal effect of nitrogen and phosphorus.Its total nitrogen removal rate was 47.76%-93.69%.The summer effluent could reach the water standard of grade III,and the effluent concentration was 0.43mg/L;the total phosphorus removal rate was 47.82.%-83.83%,and its effluent concentration is 0.11-0.3mg/L.The summer effluent reached the water standard of grade III,and reached grade?in winter;the ammonia nitrogen removal rate was 46.11%-94.00%,and the summer effluent reached the grade III.And its effluent concentration is 0.41mg/L.(5)The green zeolite matrix can stably enhance the water purification effect of the floating bed.The phosphorus removal rate of the test group containing matrix is higher than 64% in summer and reached grade IV in winter.(6)The self-purification of water bodies is mainly achieved by precipitation,adsorption and microbial degradation in water.The removal of nitrogen and phosphorus is mainly based on self-purification of water bodies,and secondly,the contribution rate of purification of plants and benthic animals is relatively small,however,it can improve the purification ability efficiently.(7)The addition of animals and plants can improve microbial abundance and community diversity.Among the floating bed microorganisms,the Proteobacteria are the most abundant.In addition,it may also affect the abundance of denitrifying bacteria.The denitrifying bacteria enriched in the floating bed matrix are mostly heterotrophic denitrifying bacteria,among which Flavobactrium,Pseudomonas and Bacillus in the TN removal process plays a major role.