Research On The Wastewater Treatment And Reuse Technology In The Service Public Buildings

The current situation of water scarcity and pollution in China is very serious.Wastewater reusing is one of the most effective ways to solve the water resource crisis and meet the increasingly stringent water environment requirements.Construction wastewater treatment and reuse has strong regional characteristic,flexibility and development prospects.Because of excessive organic matter and ammonia nitrogen pollution,which are harmful to the environment,service public buildings such as hotels,restaurants,business centers and office buildings will be punished by the environmental protection department.Although some service public buildings have installed wastewater treatment facilities,they are not in normal use due to the difficulties in adapting to the fluctuation of influent water quantity,the poor water quality of effluent water and the high operating cost.Therefore,it is of great significance to study the wastewater treatment and reuse technology of service public buildings to solve the problems.In this paper,two sets of laboratory-scale air floatation-MBR device and A/O-MBR device were used to treat restaurant wastewater and domestic wastewater discharged from service public buildings.The results indicated that the effluent water quality indexes such as COD_Cr,BOD₅,animal and vegetable oils,NH₄⁺-N,TN and TP can meet the requirements of"Wastewater quality standards for discharge to municipal sewers".The dominant bacteria at the phylum level in domestic wastewater treatment system was Proteobacteria,which contained many kinds of functional bacteria for degrading organic matter and removing nitrogen pollutants and it could also synthesize and secrete EPS which had a positive phase with membrane pollution.Therefore,it was suitable to use the combined cleaning method of surfactant+sodium hydroxide and sodium hydroxide followed by hydrochloric acid to sovle the membrane pollution problem of air floatation-MBR system and A/O-MBR system respectively.Experiments show that the membrane flux can be restored more than 80%.By comparing the effluent water quality with the water quality standard of the recycling water,the results showed that the chromaticity and BOD5 indexes can not met the requirements for non-potable use,which can be solved by adding ozone modular treatment technology and the dosage should be controlled between 2 and 4 mg/L.The TP indexes can not met the requirements for landscape environmental water use,which can be solved by adding simultaneous chemical phosphorus removal?Ferrous sulfate?modular treatment technology.In order to reduce the conductivity,Cl^-concentration,it can be solved by adding reverse osmosis modular treatment technology,which could reduce the impact of corrosion and scaling on the system.By integrating MBR combined technology?air floatation-MBR technology and A/O-MBR technology?with the above advanced treatment modularization technology,the multiple reuse requirements of service public buildings could be met.The traditional water supply project and wastewater reuse water supply project were analyzed by using the"cost-effectiveness"method and establishing economic analysis model.When the cost ratio is more than 1,the wastewater reuse water supply project is more economical.On the contrary,when the cost ratio is less than 1,the wastewater reuse water supply project is not as good as the traditional water supply project.Based on the analysis of a case of wastewater treatment and reuse in service public building in North China,the air flotation-A/O-MBR-ozone activated carbon modular treatment technology was adopted combined with the above research results.The results showed that the effect of complex wastewater treatment was good,the effluent water quality indexes such as chromaticity,turbidity,BOD₅,NH₄⁺-N,total coliform flora met the standand"Water quality standard for non-potable urban use"and"Water quality standard for scenic environment use".The results of removal efficiency of antibiotics resistance gene showed that MBR treatment unit had a good effect on eliminating ARGs.The recycling wastewater was mainly reused for building toilet flushing,virescence reuse and irrigation,and landscape fountain water,etc.After the project went into operation,the operation cost was 3.27 yuan/m³and the average water-saving amount was 420 m³/d,which could save 955,000 yuan/year.With the increasingly prominent problems of environment and water resources,not only economic benefits have been produced,but also the unified development of environmental benefits and social benefits has been realized.