Water Online

JUL 2017

Water Innovations gives Water and Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

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By Mark Reinsel I ndustrial wastewater treatment for inorganics can be as simple as settling or filtration and as complex as multistage chemical precipitation or ion exchange processes. Technologies continue to evolve; the following methodology is recommended for selecting the best technology for each application, and several proven technologies have been shown to be effective for the water quality parameters most commonly regulated. Typical parameters requiring treatment in industrial wastewater include suspended solids, dissolved metals, nitrate, ammonia, arsenic, and sulfate. This article will be a high-level examination of the treatment options available for inorganic contaminants. The same basic steps can be followed in selecting a process for most industrial wastewater treatment applications: 1. Evaluating and confirming the design criteria; 2. Reviewing potential treatment technologies to address those criteria; 3. Developing one or more process flow sheets; 4. Estimating capital and operating costs for one or more options; and 5. Performing bench and/or pilot tests. Design criteria include average and maximum anticipated flow rates, influent concentrations, and effluent concentrations (discharge permit limits). Concentrations may be unknown early in the design process but can be estimated through modeling or by examining similar sites. It is important at this point to analyze for both total and dissolved contaminants. Treatment Limits A logical starting point is to examine the regulations that determine (or are interpreted to determine) an industrial facility's discharge limits. These limits then form the basis for all of the water treatment work that follows. Effluent limits allow the environmental professional to specify treatment goals and process design criteria. Regulatory limits come from four main programs: 1. For point source discharges to surface water, National Pollutant Discharge Elimination System (NPDES) permits or the state equivalent; 2. For groundwater discharges, the appropriate state program; 3. Underground injection control program (U.S. EPA or state); and 4. Nonpoint source controls such as total maximum daily loads (TMDLs) or best management practices (BMPs). In the most common program, NPDES permits are generally required for discharge of pollutants from any point source into "waters of the U.S." An NPDES permit is essentially a license or contract for discharge of specified amounts of pollutants into a water body under specified conditions. Exceeding those specified amounts or conditions may bring legal and/or financial penalties. A point source is any discernible confined and discrete conveyance from which pollutants are or may be discharged. Examples include pipes, ditches, leachate collection systems, and publicly owned treatment works (POTWs). The term "waters of the U.S." (or State) covers a broad range of surface waters and may include hydrologically connected groundwater. This subject has been the source of numerous court cases. 10 wateronline.com n Water Innovations Industrial Wastewater Treatment Options With a plethora of contaminants deriving from a multitude of sources and a variety of treatment solutions to choose from, the topic of industrial wastewater can get complex fast. This overview provides clarity. A logical starting point is to examine the regulations that determine (or are interpreted to determine) an industrial facility's discharge limits. For Inorganic Contaminants

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