Handbook of Environmental Engineering

12Wastewater Engineering

Say Kee Ong

Department of Civil, Construction, and Environmental Engineering, Iowa State University, Ames, IA, USA

12.1 Introduction

There are more than 15 400 municipal wastewater treatment plants in the United States treating more than 32 billion gallons per day of municipal and industrial wastewaters (US EPA, 2012). To minimize environmental impact and to protect human health, these municipal and industrial wastewaters must be treated to remove various chemical constituents and toxic/hazardous compounds before they are released to the environment. As required by the Clean Water Act (1987), municipal wastewater treatment plants are required to obtain a National Pollutant Discharge Elimination System (NPDES) permit to discharge treated effluent to a receiving body of water. Effluent limits in an NPDES permit are determined using technology‐based effluent limits, i.e. based on available technology to control the pollutants, and water quality‐based effluent limits, i.e. based on limits that are protective of the water quality standards of the receiving water (US EPA, 2010). Typical pollutant limitations for municipal wastewater treatment plants include biochemical oxygen demand (BOD), nutrients such as nitrogen (ammonia and total nitrogen) and phosphorus, total coliforms, and suspended solids (SS) (US EPA, 2004). Similarly, industries discharging treated wastewater directly to a receiving body of water are required to obtain an NPDES permit. The effluent ...