Experimental Study On The Long-term Storage Technology Of Rainwater In Sea Island

In recent years,our government has carried out the island expansion project.However,at present,the fresh water supply in islands basically depends on long-distance delivery from the near mainland,which is of high cost and restricted by climatic conditions,it can not guarantee enugh supply of water on the island.Fortunately,the island is abundant in rainfall,and the quality of natural rainwater is very good,which has high potential utilization value.Utilizing rainwater provides an alternative method of solving this problem.But the dry season and wet season are very clear in sea island,most of the rain fall in wet season,so storing rainwater in wet season by storage pool become an effective measure to realize this.However,the deterioration of water caused by various exterior factors in the long-term storage process brings great inconvenience to the utilization of rainwater.Finding simple and easy-to-operate method to preserve rainwater is one of the most urgent subjects at present.In this paper,island rainfall is the main research object,contrasted by rainwater from an urban area,based on this,we carried out our research.With the reference of the quality standard of earth surface water circumstance and the national sanitary standard of drinking water,we monitored the change of rainwater quality in the long-term storage process,and explored the change law of water quality under several different physical and chemical methods.Whatsmore,the effect of potential pollutants on the water quality was studied by taking chlorpyrifos as an example.The experiment period was three months.The effects of the long-term preservation of rain water under different physical methods were studied.In this study,we used three ways,aeration only,agitation only and aeration + agitation.And the results of the experiment showed that water in the pool with aeration had gone bad badly,with bacteria booming,total nitrogen and total organic carbon rose and even exceeded the standard limit.However,the deterioration of the water quality in aeration poolsg is obviously slowed down after air preconditioning device aiming at the possible pollutans in the lab was added in the middle of the aeration pump and the pool,which meas lots of bacteria and other pollutans in the air were produced into the pools through aeration and caused the pollution.So the sanitory quality of the air should be effectively guaranteed in practical appliance.But in a whole,the addition of the physical measures made the quality of the water slightly worse when the water was clean,in which process only bacteria grew and exceed the limit while other indexs kept good.And the order of the deterioration degree is: aeration ? aeration +agitation > agitation.But for the poor-quality water from urban district in Harbin,the physical measures had shown good results.The water kept rich in oxygen,the organic substances and other pollutants in high concentration declined quickly,and this trend continued.After running under these physical measures for a week,ammonia nitrogen,total nitrogen and total organic carbon decreased a lot with highest decline of 32%?29% and 50%,which were much better than the control group.The modification degree of these measures was listed as agitation + aeration > agitation > aeration > none.These results shows physical measures has great significnace on dirty rainwater.Whatsmore,agitation become the priority especially for those sites with poor technique and low economy due to it will not introduce external pollutants easily and has a low operating and management cost,stable character.It also shows that the sanitary condition around the pool is very important to the quality of the water body.The site experiment on island also proved above conclusions.The water taken from the rainwater storage pool was fine.After ten days of storage,the permanganate index,total nitrogen and the conductivity of the water under agitation decreased,while those of the aeration pool increased.As for the clean natural rainwater,we also studied the influence of chemical method.Sodium hypochlorite was used as disinfectant.For the clean water,its initial quality is basically within the national hygiene standard of drinking water.In the process of long storage,the most likely to worsen and exceed standard was the microbe number.Mainly based on the total number of bacteria and residual chlorine.We explored the connection between the degradation of residual chlorine and the growth pf microbe,the period of disinfection and effect of the chloros on p H.We repeated the experiment in the field and find the degradation period in the filed was much shorter than that in the lab,which showed that the period of disinfection is closely related to the environment,including initial quality of water and temperarure,etc.So it will depend on the practical conditions when it comes to live appliance.Finally,the effect of the entry of potential pollutants in the island was investigated,chlorpyrifos was take as an example.We added the special pollutants by three times of the limited concentration in GB5749-2006.Then monitored and analyzed the water quality for three months.We found that the addition of chlorpyrifos made total organic carbon slightly higher,but the growth of bacteria was inhibited to an extent and the water quality kept stable.During storage,only a slight decrease of chlorpyrifos concentration was observed due to pre-stage sedimentation.