Development Of An On-line Continuous Automatic Filter And Its Application In Monitoring Of Waters

With the process of industrialization,water systems in China are generally polluted to certain levels.The eutrophication of lakes and reservoirs is particularly prominent.Therefore,monitoring the changes of nutrients and chlorophyll concentration in water is of great significance for the protection of water environment health.The conventional monitoring methods usually need a long time to complete and are impossible to reflect water quality in real time.A automatic analyzer and in-situ analyzer of nutrients and chlorophyll can realize the on-line monitoring,however,when on-line analyzers are applied in waters with high turbidity,filters providing continuous filtered water must be provided.The existing manual filters cannot continuously and automatically treat the water samples.The reported filters that can automatically replace filter or membrane are still in the laboratory testing stage and have not been applied in field.In order to overcome the deficiencies of the existing filtration methods,a new type of on-line continuous automatic filter has been developed in this study.The working parameters were optimized.It was hyphenated with nutrient analyzers and applied to the shipboard underway and on-site long-term monitoring of nutrients in Jiulong river estuary,Furong lake and Jiangdong reservoir.Based on the proposed filter,an on-line chlorophyll filtration-elution system was developed and combined with a chlorophyll analyzer to build a chlorophyll on-line filtration-elution-determination system for continuous determination of chlorophyll in waters.The main research contents and results are as follows:(1)An on-line continuous automatic filter was designed,and parts of the filter were prepared.The automatic filter was assembled and its performance was tested.The filter had the following characteristics:1)The structure was compact,the processing was simple and the cost was low.2)The filtering result was satisfied and the operation was stable.3)The filter could be hyphenated with nutrient analyzers for on-line monitoring in field.(2)The on-line continuous automatic filter was hyphenated with turbidity/nutrient analyzer to monitor the turbidity and nutrients in Fujian Jiulong river estuary,Furong lake in Xiangan campus of Xiamen University and Jiulongjiang Jiangdong reservoir,using shipboard underway method or on-site long-time observation method.The results showed that the estuary turbidity varied from 18 to 224 NTU during the monitoring at the Jiulong river estuary,and the turbidity after filtering with the filter decreased to about 1 NTU.During an on-site long-time monitoring of Furong lake and Jiangdong reservoir,the turbidity of original water of Furong lake,130 NTU,and that of Jiangdong reservoir,15 NTU,were all decreased to about 1 NTU in the filtered water.Field experiments showed that the filter was suitable to treat various waters with different turbidities,and the filtering results were satisfied for nutrient analyzers.(3)Based on the developed automatic filter,an on-line filtration-elution-determination system for chlorophyll was established and used to rapidly and continuously measure chlorophyll concentration in water.The experimental results showed that the system could quickly elute the chlorophyll collected on the membrane,and the elution efficiency of chlorophyll was 40%-60%,with an average value of 48%.As a result,0.5 was selected as a correction factor.With the chlorophyll concentration and the correction factor,a semi-quantitative or even quantitative analysis of chlorophyll in water could be realized,and the information phytoplankton biomass in the water could be provided in real time for supporting the evaluation of eutrophication.