Treatment Of Black And Odorous Water Through Optimal Combination Of Four In-situ Remediation Technologies

In recent years,the level of urbanization in China has been continuously improved,and the phenomenon of black and odor in urban bodies has become more serious,which has affected the city’s image and people’s healthy life.Therefore,treatment of black and odorous water has been highly valued by all sectors of society.This paper took simulated black and odorous water as the treatment object,investigated the oxygenation technology,microbial inoculant technology,biological carrier technology and plant floating bed technology to treat black and odorous water,and determined the best operating conditions for single treatment technologies.Based on oxygenation technology,supplemented by microbial inoculant technology,bio-carrier technology and plant floating bed technology,the purification effectiveness of single technologies was studied.Analytic hierarchy process（AHP）was used to establish a comprehensive evaluation index system for constructing a black and odorous water purification model,and selecting the best technical combination scheme,which was finally applied to an U-shaped simulated river pilot.The main content and results are as follows:（1）Treatment effectiveness of single technology on black and odorous water.The optimal strategy for oxygenation is in continuous mode,with the intensity of 0.08 L/min.The optimal dosage for microbial inoculant is 3 mL,with the of 1/10,000.The best type of bio-carrier is basalt fiber bio-carrier,with the laying density of 10 bundles/m².The optimal type of plant floating bed is the Iris pseudacorus plant floating bed,with the laying density of 10 plants/m².Among the technologies,oxygenation in continuous mode achieved the best effectiveness at the intensity of 0.08 L/min.（2）Treatment effectiveness of combined technologies on black and odorous water.The combination of oxygenation+basalt fiber bio-carrier,oxygenation+microbial inoculants+basalt fiber bio-carrier and oxygenation+microbial inoculants+basalt fiber bio-carrier+Iris pseudacorus plant floating bed were preferentially selected for involving two,three and four technologies.For four-technology combination,chemical oxygen demand（COD）,ammonia nitrogen（NH₃-N）and total phosphorus（TP）removal efficiencies were 68.9%,99.1%and82.2%in the summer test,and 68.5%,99.2%,and 86.8%in winter test.Compared with the test group of two-technology and three-technology combinations,the time required to reach stable COD,ammonia nitrogen and total phosphorus removal efficiencies in the four-technology was shortened by at least 0,2 and 4 days in the summer test;and 6,2 and 0days in winter test.（3）Strategic optimization of technology combination for black and odorous water remediation.AHP is used to establish a comprehensive evaluation index system for black and odorous water treatment technology,which determine the weight of economic indexes,pollutant purification effectiveness and landscape beautification and other sub-targets in the total and carry out non-quantitative treatment on the evaluation indexes.By means of comprehensive evaluation,the optimal scheme for treating the black and odorous water was selected as the combination of oxygenation+microbial agent+basalt fiber biological carrier+Iris pseudacorus plant floating bed technology.The optimal cost-effective solution was the combination of oxygenation+basalt fiber biological carrier technology.（4）Pilot test for U-shaped simulated river channel.The four-technology combination of oxygenation+microbial inoculants+basalt fiber bio-carrier+Iris pseudacorus plant floating bed were applied to the U-shaped simulated channel,and the water quality change of the U-shaped simulated channel was predicted by the fitting equation of pollutant removal efficiency.The results show that the initial concentration of COD,ammonia nitrogen,and total phosphorus in the water of the U-shaped simulated river channel changed from 91.4 mg/L,29.1 mg/L,and 1.7 mg/L to 22.32 mg/L,0.3 mg/L and 0.1 mg/L,with removal efficiencies reaching 74.6%,98.8%and 94.3%.The water quality indicators of each pollutant met the surface water environmental quality class III water standard.This shows that the four-technology combination has a good treatment effectiveness.The simulated results agreed well to fitting equation,demonstrating that the fitting equation can better predict the pollutant removal efficiency in U-shaped simulated rivers.