Research On The Mid-water Reuse For Dalian Beihai Thermoelectricity Generation Company

Mid-water which can be reused within some range mainly includes the civil and municipal wastewater which has been treated, reaching some standard which is between that for drinking water and wastewater. That is why we call it mid-water. In recent years, the mid-water development and mid-water recycling have been developing rapidly, which is very popular in America, Japan, India and Britain. All these countries adopt effective technology for mid-water recycling according to the situations of their countries, making the technology of mid-water recycling become more and more perfect. The processing method for mid-water recycling adopts different processing units on the basis of components of pollutants, mid-water use and requested water quality in order to meet the standard, which mainly includes elementary treatment, secondary treatment, sand filtration, chemical clarification activated carbon adsorption, reverse osmosis or other methods of removing ion, disinfection.In this experiment, mid-water from Chunliu Wastewater Treatment Plant was sent to a moving-bed bioreactor to wipe off organic substance and nitrogen and phosphor nutritive salt through biological oxidation degradation. Moving-bed bioreactor is kind of effective bioreactor with high volume load and degradation ratio for organics. Water from MB got into sedimentation pool through gravity with polymer aluminium in order to wipe off the ageing biologic membrane. Then water was taken out to fiber filtration to eliminate the bigger suspended substances with a pump, and water from fiber filtration went into activated carbon adsorption pool to eliminate the smaller suspended materials and rudimental organics further. Treated water from activated carbon adsorption tower entered the reverse osmosis system through a filter to remove salt and rudimental organics.The experiment lasted for about 300 days intermittently. The SDI for pre-treated water is less than four, which is in line with the requirement of Reverse Osmosis; conductivity of water from RO was controlled under 50us/cm while desalting ratio is about 92%; the attenuation of membrane flux was within the limits stipulated by the design handbook. Furthermore, because of the use of traditional filter, there was no special demand for advanced experimental instrument. But it was still in a position to ensure produced water to reach the standard of cooling water for boiler stipulated by Dalian Beihai Thermoelectricity Company.