Research On The Algae Removal By Combined Chemicals In Eutrophic Water

Recently, eutrophication in surface water is more and more serious in China.Algal blooms pose serious risks for human and animal health, aquatic-ecosystemsustainability and economic vitality. Based on the preliminary investigation results ofalgae species on four waterbodies with different functions in Xiamen, a newefficiency, low toxicity and low cost combined chemical was developed. It wasapplied for emergency control of algal blooms. The acute toxicity and themechanisms of algal inhibition were analyzed. Meanwhile the effects ofenvironmental factors on the algaecide and the economic benefit were studied. Andthe removal efficiency of algae by copper sulfate complex was assessed.The minimum dosage of nano zinc oxide, aluminum compound, coppercompound, ferric compound and potassium permanganate were separately10mg/L、30mg/L,0.2mg/L,5.17mg/L and1mg/L when removal efficiency of algae was50%in eutrophic Lake Bailu. The removal efficiency of Diatom and Cyanophytawere high by copper compound. While the removal efficiency of Chlorophyta washighest among three algae species treated by ferric compound. The removalefficiency of different algae by potassium permanganate followed the order:Diotam>Cyanophyta>Chlorophyta.Four algaecides with different formula had been screened out. Copper compoundcombined with aluminum compound was more effectively on algae removal. Whilealuminum compound combined with potassium permanganate and three chemicalsmixed were less effectively.The optimal weight proportion of copper compound and aluminum compoundwas0.2:15. It was pointed out that the optimal combined chemical could removalalgae, turbidity and phosphorus simultaneously. The removal efficiency of differentalgae followed the order: Diotam>Cyanophyta>Chlorophyta. The removal efficiencyof algae was higher than80%in ten days when combined chemical was applied asalgaecide. The water temperature and pH value had influence on removing Chlorophyta. The removal efficency of algae was free form CODMncontent of rawwater.The mechanisms of algae inhibition were that combined chemical can passthrough the cell wall and change membrane permeability and lead oxygen radicalenter to inhibiting or killing algae by SOD, MDA and protein concentration changed.The acute toxicity of combined chemical was assessed with luminescent bacteriatoxicity test. The water was low toxicity after treated by combined chemical with thedosage less than30.4mg/L. The cost by dosing combined chemical was0.011～0.018Yuan/d·m~3.The removal efficiency of imported copper sulfate complex was assessed byfield test for174days. Algal blooms was effectively put under control after theapplication, with concentration of chlorophyll a falling from298.98μg/L to40.71μg/L and the turbidity from14.45NTU to5.70NTU. Various organs of Tilapia sp.followed the order: liver (512.50mg/kg)>gill (17.00mg/kg)>muscle in copperenrichment ability.