Study On Removal Technology Of Pyrethroid Pesticides And Algae In Water

As the urbanization speed is becoming faster and faster, Agricultural intensification and farmers ’ living standards become increasingly higher, surface drinking water sources’ pollution load is increasing, too. Water pollutants are vary, for example: the pesticide applicated for farmland which around the sources will get into the water with precipitation; the N, and P concentration exceeded in waterwill led to water eutrophication and cause algae large breeding eaasily; industrial wastewater produced from factory nearby may get into drinking water through soil or precipitation, making water suffered the pollusion from metal toxicity material, aldehyde, ketone, and phenol; the water may contain many pathogens,such as virus, germs, and parasites, which will pose a hazard to health.Southwest mountainous area is remote andfew industrial waste water can get into drinking water sources, the contamination mainly comes from agricultural non-point source pollution, especially the pesticides and algae. Due to the economic backwardness of many rural areas from Southwest mountainous areas, water treatment plant infrastructure is not perfect, routine coagulation, sedimentation and filtration processes cannot make fundamental improvement in water quality and many areas can only use the micro-polluted water as drinking water or for other purposes. Therefore, this paper examines the removal effect of the algae and pesticide by the technology of enhanced coagulation, providing technical support for the construction and operation of southwest mountainous areas’ water treatment plant.The content of this paper includes the following three main aspects: 1)the small pilot experiment of the pyrethroid pesticides removal by enhanced coagulation; 2) the small pilot experiment of the algae removal by enhanced coagulation 3))the pilot scale experiment of the water sources’ algae removal.The findings of the enhanced coagulation process to removing pyrethroid pesticide experiments show that when only add coagulant to deal deltamethrin water samples,the PAC is the best coagulant, the 18mg/L is the optimal dosage,the optimum PH range is 6~9 and the maximum value of the deltamethrin removal is approximately 64.5%. The effect of removing deltamethrin by PAM to PAC coagulation is better than that of sodium silicate.The optimum dosage of removing the deltamethrin by oxidation KMnO4 is 0.6mg/L, the optimum PH range is 4~7 and the best oxide time is 25 min.After applicated optimal coagulation-oxidation in optimal condition to treat deltamethrin water samples,the maximun removal of deltamethrin reached 82.4%.When only add coagulant to treat fenpropathrin water sample, the best efficiency of removing fenproathrin is by using ferric chloride.When the optimal dosage is 20mg/L, the optimum PH is 8, the maximum removal of removing fenpropathrin is about 56.6%. The dissolution effect of fenpropathrin is close to zero by using coagulating sedimentation method to remove the fenpropathrin in the first seven days.The activated carbon in wood power for fenpropathrin has a good adsorption removal when the PH is 6~9,the best dosage of activated carbon to removing fenpropathrin is 40mg/L, the optimum adsorption time is 60 min. Langmuir model can better describe the temperature process of fenpropathrin adsorption on activated carbon.After first five days of activated carbon adsorption to removing fenpropathrin,the desorption efficiency is zero.,The fenpropathrin removal rate stabilized at 90% when using the above test to determine the optimum parameters of coagulation and activated carbon adsorption to remove fenpropathrin, and using optimal conditions of coagulation and activated carbon adsorption.The small pilot study of the enhanced coagulation process to removing algae shows that,when dosing the algae water samples with separate dosing coagulant, the PAC is the best for removing turbidity and chlorophyll-a,and the best dosage is 40 mg / L and 35 mg / L. When the pH is between 7-9, the PAC is the best for removing turbidity and chlorophyll-a. From the practical and economical point of view, the coagulation of kaolin is better than diatomite’s and the best dosage is 30 mg / L. The Chlorophyll-a removal rate increases by 1.2% to about 97.7% when compared to the water sample only coagulated and coagulated after dosing KMnO4.After adding water samples with KMnO4, turbidity removal efficiency dose not change significantly.The best dosage of KMnO4 is 1.5mg / L, the optimum oxidation time is 40 min.Pilot test results show that when only add coagulant to removing chlorophyll-a, turbidity, ammonia, total nitrogen, TOC, the best coagulant is PAC, its optimum dosage is 30 mg / L. The best coagulant is diatomite and the optimal dosage is 30 mg / L. Removal of coagulant effect, The effect of KMnO4 in removing chlorophyll-a, turbidity, TOC is better than that of bleach,and bleach is better in removing NH4+-N and TN than that of KMnO4. A month’s running of the pilot test equipment shows that biological contact oxidation pond, flocculation and sedimentation tank, no valve filter, activated carbon adsorption pool can help to remove chlorophyll-a, turbidity, NH4+-N, TN, TOC and the final water is less than "GB 5749-2006 drinking water health standards" for these types of indicators limits, meeting drinking water requirements. By each index variation along the test of the biological contact oxidation pond,the support layer is the best one to removal of ammonia, then is turbidity. But the TN and TOC removal is not good. a of Chlorophyll-a increased after the treating of supporting layer. Shale suspension filter layer’s removal of chlorophyll-a, turbidity and TN is better and the removal efficiency is relatively poor for NH4+-N and TOC.