Developement of processes for nutrient removal from wastewater

This review focuses on techniques for achieving very low concentration of TN and TP in water.The 1970 Clean Water Act in the US and the Urban Waste Water Treatment Directive in Europe now provide the benchmark standards for TN and TP levels.Arden and Lockett discovered activated sludge in the 1910’s.Since then,many improvements have been made to the biological treatment process to provide various configurations that have the ability to deliver effluent concentrations between 6-8mg TN/L and 0.5-1.0mg TP/L,without external carbon addition.Typically,however,additional advanced nutrient removal technologies are used in tertiary treatment to meet more stringent effluent quality requirements.One advanced technology that has been successfully implemented in the US is denitrifying filters.For TP removal,tests showed that the BlueP RO and CoM ag systems both reliably met an effluent target as low as 0.04 mg TP/L.However,the establishment of stringent TN and TP effluent limits will dramatically increase the capital and operational costs of wastewater treatment plants.A more promising nutrient capturing process is based on the assimilation of nutrients(both N and P)during heterotrophic growth which uses a carbon source for energy.Laboratory trials of the single step process by Reach Green suggest that concentrations as low as 0.5 mg TN/L and 0.02mg TP/L are readily achievable.