| Reclaimed water,as the second water source of a city,will undoubtedly have important influence on protecting the environment and economic development.The shortage of freshwater resources is one of the main factors that restricted the economic and social sustainable development of Qingdao.In order to alleviate the pressure of the water supply,solve lack of reclaimed water utilization and further enhance the ulitization ratio of recycled water problem,it is very necessary that investigates and analyzes the water quality on the effluent of the main wastewater treatment plants in Qingdao and researches further advanced treatment process optimization of the effluent qualityThis paper takes five large city wastewater treatment plants in Qingdao as the research object.Facing the insufficient reclaimed water reuse rate,water quality identification and its regeneration utilization potential evaluation were taken after twostage water quality investigation on the effluent of the five wastewater treatment plants,and the restrictive indicators ahout the recycling of the effluent was also analyzed.Besides,sodium hypochlorite and potassium permanganate oxidation manganese technology was studied in order to solve the water problems of manganese exceeding of the effluent of A wastewater treatment plant that limited its effluent to recycling for flushing,car washing water.The research mainly includes as follows:(A)The reclaimed water recycling potential survey analysis of typical wastewater treatment plants in Qingdao.They were done by two-stage water quality investigation and the analysis of the restrictive water quality indicators.(B)The feasibility analysis of chemical oxidation manganese removal technology.To axoid the problems causing by the manganese exceeding,that limited its effluent cannot be reused for flushing,car washing and industrial water.The feasibility analysis of sodium hypochlorite and potassium permanganate oxidation manganese technology was investigated and main factors were determined.(A)The reclaimed water recycling potential survey analysis results are as follows:when the water temperature was higher,under the condition of existing water quality,the reffluent of B,C,E sewage treatment plant could be used directly back to city miscellaneous water and landscape environment water.Because of excessive manganese,the effluent of A sewage treatment plant couldn’t be directly used for flushing,car washing water,and because of excessive ammonia nitrogen.The effluent of D sewage treatment plant wasn’t directly suitable for urban miscellaneous water.As a result of chloride exceeding standard,the effluent of the sewage treatment plant was not directly suitable for recycling to industrial water.For total nitrogen levels,the effluent of A,D sewage treatment plant couldn’t be directly used for landscape water.When water temperature was low,the water quality of the effluent sewage treatment plant was declined.The exceed standard of hardness,sulfate,manganese and TDS furtherly restricted the effluent of the city sewage treatment plant applying to the urban greening,flushing,car washing and so on.As a result of chloride and manganese sulfate,hardness and TDS exceeding standard,the effluent was not directly suitable for recycling to industrial water.The effluent of A,D sewage treatment plant couldn’t be directly used for landscape water.The biological toxicity analysis results shows that the effluent’s acute toxicity of A,B,C,sewage treatment plant were high toxic,poisoning,poisonous,stimulation and low toxicity.The genetic toxicity test results show that the all sewage treatment plants were moderate pollution.(B)The feasibility analysis results of chemical oxidation manganese removal technology are as follows:The higher the temperature and p H,the faster the reaction rate of the sodium hypochlorite manganese removal.The active chlorine dosing quantity relation with the change of initial manganese concentration in A wastewater treatment plants were respectively the Y=6.3306 ㏑(x)+24.377.Filtering after reaction for 90 minuts,the manganese concentration in water could be dropped below 0.1mg/L If choosing the way by dosing PAC coagulant to achieve the purpose of manganese removal rather than filter,the optimizing dosage were 17mg/L.Rapid mixing time was 20 seconds,and speed was 100 rpm.Slow mixing time was 9.77 minuts and speed was 40 rpm.Settling time was respectively 10 minuts.The effect of temperature on potassium permanganate method of manganese removal was less,but the p H was more.The potassium permanganate dosing quantity relation with the change of initial manganese concentration in A wastewater treatment plants were respectively the Y=6.3306 ㏑(x)+24.377.Filtering after reaction for 30 minuts,the manganese concentration in water could be dropped below 0.1mg/L.If choosing the way by dosing PAC coagulant to achieve the purpose of manganese removal rather than filter,the optimizing dosage were 45mg/L.The coagulation mixing conditions was the same.Settling time was respectively 30 minuts. |
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