Study of Capability of Zebra Mussel (Dreissena polymorpha) in Reduction of Nitrate and Phosphate in Urban Waste Water (Open System)

Document Type : Original Articles


1 Department of Environment, Faculty of Environment and Energy, Science & Research Campus, Islamic Azad University

2 Department of Environment Faculty of Natural Research, Tehran University


Dreissenapolymorpha (Zebra mussel) is a fresh water mollusk and native species of Caspian Sea area. These shells belong to filter feeder class and are able to filter a great volume of water. In this research, due to a wide range of materials available in urban wastewater efficiency of Dreissena polymorpha is studied to reduce concentration of Nitrate and Phosphate. The shell masses in 20, 40 and 60 g were put test for filtration tests and indirect absorption of nitrate and phosphate from artificial wastewater. These tests were performed in open system and were repeated 3-10 times depending on variance range.The results showed that there is a positive correlation between the weight of shell masses and the filtration rate of Nitrate and Phosphate in open system (R2 =0.99) and there is a negative correlation between concentration of Nitrate and Phosphate at the wastewater entry on one side and the filtration rate of nitrate and phosphate on the other side (R2=0.97) (t=2.132, P<0.023). It was found that when the weight of shell masses increase (from 20 to 40 to 60 g), the amount of Nitrate absorption is 0.08-0.2 mg.l-1 while Phosphate is absorbed 0.02-0.04 mg.l-1 in the open system. In this research it was found that Chlorella and Scenedesmus algae are able to reduce concentration of Nitrate (of at least 0.03 to 1.73 mg.l-1) and the Phosphate solved in waste water (of at least 0.42 to 4.48 mg.l-1).