Study On The Treatment Of Polluted Landscape Lake Water

The polluted landscape lake water,because of its poor liquidity and other characteristics,as its self-purification ability is limited,when the pollution load is greater than the self-purification capacity,the water quality will become poorer,and cause the deterioration of the whole environment of the lake.In addition,there are many problems might be caused,such as eutrophication,organic matter accumulation and the growth of algae could lower the transparency of lakes,thereby destroying the landscape.In this study,Biological Aerated Filter(BAF)-Double Layer Filter was used to treat the polluted lake water in Guangzhou.Small-scale experiment shown that: the best operating conditions was: C/N=5,filtration rate=4m/h,air-water ratio=1:1.On this condition,for the ceramics-BAF-Double Layer Filter unit,the removal rate of CODcr,NH3-N,TN,Turbidity and Chl-a was 52.9%,89.0%,83.4%,76.4%,76.1% respectively.For the oyster shell-BAFDouble Layer Filter equipment,the removal rate of CODcr,NH3-N,TN,Turbidity and Chl-a was 47.1%,81.1%,76.0%,75.7%,76.5% respectively.In addition,the oyster shell unit was not stable,comparing to the ceramics one.In practical application,ceramsite filler is still recommended.In order to further save the operation cost,in this experiment,through the large amount of DO produced by algal during the day time,the BAF process could stop aeration in the day and restart it at night.When the fitration rate=8m/h,packing layer height=2m,air-water ratio=0,the process could stop aeration for the maximum of 10 hours,at the same time,saving the energy of the blower about 40%.To solve the problem of the algal in the lake,this research developed a terrestrial plant-made reagent to control the algal by using the Syzygium cumini fresh leaves and defoliation.The result showed that,within 15 d,the inhibition rate of M.aeruginosa could reach 98%,which was a good result.In order to further study the mechanism of algal inhibiting,the researcher used phyto-PAM,flow cytometry,3-dimensional fluorescence spectra to test the process of inhibition.Result showed that the reagent made by Syzygium cumini could strongly inhibit the Fv/Fm,YII,? and rETR during 1~4d,then gradually recovered;The result of flow cytometry showed that,in the early stage of the experiment,the inhibiting effect tend to be ‘algistatic';in the later,the extract could detroy part of the membrane of the algae,which presented the mechanism of the extract on algae growth control was ‘algicidal';The extract could strongly inhibited the esterase activity of the algal cells within1~5d,the maximum inhibition rate was over 90%,which lower the metabolic activity of the algal;The 3-dimensional fluorescence spectra showed that,there were two kinds of substance in solution: microbial metabolic by-products and humic acid.The allelochemicals might exist in this part of the humic acid compounds;Intensity of humic acid gradually became weak in the later,might lead to degration of allelochemicals,which might be the reason why the extract couldn't inhibit the algal for a long time.So in practical use,might need to add this reagent to the water more than one time.In order to treat the polluted lake water,a BAF-Contact Oxidation Tank system was built near the lake.The system could purify 6750 t polluted water per day.The optimum operation condition was:fitration rate=4m/h,air-water ratio=1:1.On this condition,the system continously ran for a whole year,the quality of the lake water could reach Class IV standards,Chl-a declined 10 ?g/L compared to last year the same month.The water transparency up to 0.40 ~ 0.58 m,the whole ecological environment of the lake recovered well.