Study On The Storage And Recycling Of Rainwater From The Campus’s Combined System

On current, global water resources is so grim, more and more researchers notethat university is a major water user which has high population density. Waterconservation, water recycling becomes the main content of water environment systemplanning on campus. The storm water, fountain water and mixed water shouldcompose the recycling system, for the purpose of water conservation and waterrecycling. Hunan University is located in Hunan province which has long rainfallseason and rich rain water, so the recovery and utilization of rain water resources willbecome an economical and practical way to develop water resources. It has practicalsignificance, urgency and certain feasibility to establishment a rainwater treatmentand reuse systems in the campus. In order to research the combined sewerage systemin the rainwater treatment and reuse system, the experiment studies on comparison oftraditional flocculation-sedimentation and MBR （membrane bio-reactor）. Theoptimum operating parameters of two processes can be determined in different waysby the study on reservoirs of different water treatment on campus with the traditionaltechnology and the membrane bioreactor experimental.In this experiment, we determined to collect the raw water from the pond, whichis located in Denggao Road and near the gate of the Mount Yuelu, to study andexplore the specific methods of treating the pond water.Test results show that theconsequences by PAC as a coagulant is better than the consequences by ferroussulfate as a coagulant; with the rise of pH, the effluent pollutant index （COD, BOD₅,TN, TP, NH3-N, turbidity）firstly decline sharp and then rise slowly, at pH7.5,flocculation and sedimentation achieve the best results, and the water quality meetthe requirements of urban recycling Miscellaneous Water Quality Standard（GB/T18920-2002）; As the coagulant dosage increases, the effluent pollutant index（COD, BOD₅, TN, TP, NH3-N, turbidity）firstly decline sharp and then rise slowly,when the PAC dosage is0.88mg/L, flocculation achieves the best results. In thisexperiment, the sewage treatment is affected by the temperature, the result is better insummer than in winter; when flocculation velocity gradient is60r/min, the pollutantsremoval efficiency of raw water is the best. The results of the raw water treatmentwith membrane bioreactor showed that: temperature in winter and summer has littleeffect on the test, and the removal effect is essentially the same; the optimumaeration time is7-10h, pollutants in the raw water （COD, BOD₅, TN, TP, NH3-N, turbidity）removal efficiency is highest and the water quality is good enough to meetthe requirements of urban recycling miscellaneous water quality standards; It has alsoachieved the best results, when the gas-water ratio is about60:1.The experimental studies have shown that: if the rainwater is stored, treated withmembrane bioreactor in the campus combined sewer system, and reused, tap waterresources will effectively be saved. It has great significance of cutting cost, and thepurpose of water conservation and water recycling can be achieved.