A Study On The Plan Of Water-saving Ecological Village In Lanzhou New Area And The Reclaimed Water Reuse Technology

As the fifth state-level area approved by the State Council, Lanzhou New Area is locatedin the northwest of China, an area where water shortage is serious. Therefore, it isindispensable to build the water-saving ecological village which, as the main part of a city,has certain social and economic benefits for the construction of Lanzhou New Area, andwhich also serves as a leading role for the construction of the water-saving ecological villagein Northwest China, and as a result, it has a realistic significance to alleviate the pressure ofurban water.From the perspective of the status quo and present problems of Lanzhou New Area, andthe experience of water-saving ecological district planning both at home and abroad, thisthesis offers a reasonable construction planning for the water-saving village in Lanzhou NewArea, that is, to plan the water-saving village according to the ecological, systematic,economic and sustainable principle. Firstly we should increase the water-saving awarenessamong residents in the neighborhood, use water-saving appliances, and strengthen the effortsto supervise the whole water system. Secondly, we should use the MBR process for waterreuse, process miscellaneous drainage, and then use it back to flush the toilet, landscape, andwash the car, etc. to maximize water resources; rainwater should be collected into the lake asthe artificial lake supplemental water and the source of reuse water; moreover we shouldprovide protection for the landscape water body in the residential area and adoptcorresponding measures to prevent water from deterioration. In order to maintain the balanceof the village’s whole water system and build the water-saving ecological village, we shouldimprove the management and ensure maintenance, formulate corresponding laws andregulations, and promote the residents’ awareness of water saving. In this way we can buildthe ecologically civilized, environment friendly new water-saving district.After analyzing the domestic and foreign references and experience, this researchdecides to take the MBR process as the core technology of water reuse, investigates thevillage sewage treatment effects of each process through the experimental study on aSubmerged MBR process, A/O-MBR process and the improved BCOR-MBR process, andanalyzes the processing result. COD, ammonia nitrogen, total nitrogen, total phosphorusremoval rate of a Submerged MBR process were,92.07%,99%,22.69%,22.20%respectively;the average effluent concentration is that turbidity is all less than0.26NTU, ammonianitrogen≤2.56mg/L, COD25mg/L≤49.58mg/L, total nitrogen≤49.58mg/L, totalphosphorus≤3.32mg/L, and water indicators meet the standard of the Urban Mixed WaterQuality（GBT18920-2002）. We add anoxic zone on the integrated MBR, adopting the A/O-MBR process, and weset the hydraulic retention time of2.8h in anoxic zone, dissolved oxygen lower than0.2mg/L;hydraulic retention time in aerobic zone is6h, dissolved oxygen in aerobic zone is usuallybetween3to5mg/L. In the whole operation cycle, effluent turbidity remains low, averageeffluent water is0.24NTU, and the water quality is better, which proves the membrane playsan effectively intercepting role. Comparing to a submerged MBR, COD removal efficiencywas close to it, the average removal rate being93.78%, and the system runs stably with stronganti-impact force; ammonia nitrogen removal rate also maintains a high level, more than98%;effluent ammonia nitrogen were always less than2mg/L. The reason is that we regularlyremoved mud which has a great impact on it because the nitrifying bacteria generation cycleis long. The removal efficiency of the total nitrogen and phosphorus has improvedsignificantly, the original average of total nitrogen from22.69%to40.44%, the originalaverage of total phosphorus from26.20%of41.39%.The BCOR-MBR process（Biological Contact Oxidation Rector-MBR）will be used forthe treatment of village water reuse, and the polyurethane foam which has large porosity andspecific surface, a cube with the side length of20to25mm, is used for packing; the density islighter than water, floating on the surface of water, putting it inside the spherical hollowplastic ball; packing filling volume accounts for about50%of the entire reactor. Theoperating conditions adopted the best parameters validated by a submerged MBR process;water indicators: average removal rate of COD is94.24%, and the late effluent COD is lowerthan15mg/L; the removal rate of ammonia nitrogen is as high as99.25%, effluent ammonianitrogen under1.9mg/L; TN the water average is44.58mg/L, the effluent average rate36.24%; average total phosphorus removal rate is43.58%; the average the water is2.4mg/L.Membrane fouling is the inevitable problem of the MBR process, and we try to mitigatemembrane fouling by analyzing the reasons of membrane pollution. Membrane foulingcontrol methods include the low voltage operation, aeration, backwash, membrane cleaning.Membrane cleaning methods include spirit blunt, gas water backwash, drug cleaning,ultrasonic cleaning, etc. Membrane cleaning tests have been carried out during the experiment,we adopt the chemical cleaning method, removing the diaphragm and colloidal substances onthe surface of the organic matter, reducing membrane pollution, recovering of membrane flux.