Experimental Study On The Municipal Wastewater Treatment By Integrated Physical-chemical Technology

At present, most of the existing and newly-built urban sewage treatments in our country use the technology of secondary biological treatment, with the problems of energy-consumption and money-consumption. Besides, the process is difficult to meet the increasingly stringent emission standard. In order to reach the emission standard by means of the traditional technique method, further "tertiary sewage treatment" such as coagulation precipitate and filtering should be needed, which also increased construction investment and running costs of the system. Based on this situation, this study discussed the effectiveness and feasibility of urban sewage treatment with complete physical-chemical method in our country.The main purpose of this paper is to study the treatment effect using physical-chemical method. The common used chemical flocculants, adsorbents, and natural and modified mineral materials with comprehensive physical-chemical treatment effect were selected as the experimental materials. Screening of optimal reagent and material, as well as the factors and treatment effects of coagulation-precipitate, MAP chemical precipitation, adsorption and ion exchange process were studied via batch test and dynamic model test, in order to provide theoretical support of design and operation in actual project.The results showed that the most appropriate raw water quality for enhanced coagulation-sedimentation method was CODCr below 300 mg/L. Suspended and colloid pollutants in sewage were the main removed substances. During the experiment, removal efficiency of CODCr and TP were more than 75% and 90%, respectively. Among them, the best enhanced coagulation-sedimentation effect occurred at using the combination potion consisting of with PFS (70mg/L) and heat modified bentonite (10mg/L).MAP chemical precipitation achieved 65-75% of ammonia-nitrogen removal efficiency. And the removal efficiency of CODCr, ammonia-nitrogen and TP using MAP-coagulation coupling sediment technology can reached 74.7-79.7%,73.4-79.7%,87.4-92.1%, respectively. Zeolite modified by NaCl possessed a good adsorption effect to ammonia nitrogen, which achieved a removal efficiency of 55-65% to ammonia-nitrogen in urban sewage.The complete physical-chemical method combined by MAP chemical added with coagulation-sedimentation coupling model and filtration-adsorption technology for urban sewage possessed a highly efficiency of removing CODCr, ammonia-nitrogen, SS and TP from sewage, with an average removal efficiency of 83%, 90%, 96% and 92%, respectively. The pH of effluent was below 8.0. Each index of effluent reached the primary standard level A of discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002). Moreover, the infrastructure investment of this technique is merely half of the existing wastewater treatment technique, with comprehensive running costs of only 0.28-0.39 yuan/m3.In sum, the complete physical-chemical method is an efficient treatment method for pollutants in urban sewage. When the inlet concentration of CODCr was less than 300 mg/L, the effluent can reached primary standard level A, with a dramatically reduced infrastructure investment and running costs. Since the municipal sewage of large area in China belongs to the category of low concentration, the method discussed in this article possesses a broad application prospect.