In this research, the economic and technical method of power plant wastewater treatment and removal of heavy metal (specially in Sahand wastewater) has been studied. The result indicate
quality and quantity of that wastewater in power plant depend on the type of fuel, combustion units capacity, their operation and material used in this structure. Common point in wastewater is that any of them is not permanent and all of them are periodic.
In this research ,PH changes and flocculation and coagulation are being used to study the removing of heavy metals. Therefore, with similar artificial wastewater characteristics for preheating air and chemical washing boiler wastewater of Sahand power plant wastewater prepared. It should be mentioned that there are heavy metals only, in preheating air and chemical acidic washing boiler wastewater. Hence removal percent of heavy metal in mentioned wastewater and in the other wastewaters is studied to define the acidity neutralization.
In poisoned air preheating wastewater and acidic washing boiler wastewater treatment, following the method of precipitation of heavy metals in basic PH, at first pH of two wastewaters is raised to 8,9,10 with addition of caustic soda. In this step removal percentage of heavy metals measured in atomic absorption method, illustrates in air preheating wastewater with PH =9 and in acidic washing boiler wastewater with PH =8 the most removal percentage of heavy metals obtained.
In air preheating wastewater and with PH =9, removal percentage of Fe, V, Ni, Cu respectively is equal to 99.88%, 93.54%, 99.77%, 95.73% and in acidic washing boiler wastewater with PH =8 the removal quantity of Fe obtained 99.65%.
Hence, in order to obtain more removal percentage of heavy metals and reaching to Iran environment standard, treatment was continued with flocculation and coagulation method by using Ferric chloride, Ferric sulfate and Alum in 4 concentrations 25, 50, 75, 100.
In air preheating wastewater, after atomic absorption test on these samples and evaluation of
results, it was obvious that the most removal percentage was obtained by adding of alum with concentration of 25 mg/lit. In this condition the removal percentage of Fe, V, Ni, Cu respectively is equal to 99.98%, 99.99%, 99.97%, and 99.89%.
In acidic washing boiler wastewater the most removal percentage was obtained by adding Alum with concentration of 50 mg/lit. In this condition the removal percentage of Fe was equal to 99.98
Acidic amount in basic wastewater treatment was measured and for neutralization step, sulfuric acid was added to wastewater. In preparation boiler surface wastewater, aeration method was being used in order to removal Ammonia. Ammonia quantity in Wastewater can be recognized from its order. But after aeration in 0.5 hour, the quantity is decreased and the odor is no more recognizable. After finishing aeration for neutralization step, sulfuric acid was added to wastewater.