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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process, while denitrification is anaerobic. Suspended growth is best used for relatively low contaminant concentrations. In a suspended-growth system such as activated sludge processes (also aerated lagoons and aerobic digesters), wastewater surrounds the free-floating micro-organisms, gathering into biological flocs. The settled flocs containing bacteria can be recycled for further treatment. Suspended-growth systems typically operate poorly when encountering highly variable waste streams. Suspended-growth systems also require more energy, more equipment maintenance, and are more complex to operate because they involve more equipment than attached-growth systems. However, attached-growth systems typically require more land, may have odor issues associated with media clogging, and may be unable to treat high wastewater flows. Consequently, urban wastewater facilities often opt for suspended-growth processes, while attached-growth processes are common in small- to medium-size operations. Bench or pilot testing will usually determine whether the selected technologies can meet the discharge limits and may be required or "suggested" by the regulating agencies. These tests can also provide valuable information for estimating full-scale capital and operating costs. Treatment evaluations can range from jar tests performed in a day (Figure 4) to column tests lasting weeks or months. Emerging Contaminants Of Concern Potential emerging inorganic contaminants of concern (COCs) include: • Methylmercury, which is one of the EPA's National Recommended Water Quality Criteria. • Radon. A maximum contaminant level (MCL) is being developed by the EPA. • Cobalt, molybdenum, strontium, tellurium, and vanadium. All are included in the EPA's Contaminant Candidate List (CCL) 3. • Sulfate, aluminum, chloride, iron, manganese, and TDS. These all currently have secondary drinking water standards. • Electrical conductivity and sodium adsorption ratio (SAR). These parameters are of concern in coalfield-produced water. Emerging Technologies Emerging technologies for inorganic contaminants include: 1. Biochemical reactors for removal of sulfate, TDS, and dissolved metals. 2. Enhanced solar evaporation. 3. Innovative nitrate removal technologies. 4. Innovative arsenic removal technologies. Summary Physical, chemical, or biological processes can be used to remove inorganic contaminants from industrial wastewater. Common parameters requiring treatment include suspended solids, dissolved metals, nitrate, ammonia, arsenic, sulfate, and TDS. Prior to selecting a process and designing a water treatment plant, potential treatment technologies should be investigated and bench and/or pilot tests performed. Recommended technologies for inorganic contaminants commonly found in industrial wastewaters are: • Suspended solids: clarification and/or filtration; • Dissolved metals: hydroxide precipitation, sulfide precipitation, or ion exchange; • Nitrate: attached growth biological processes (denitrification) in almost all cases; • Ammonia: attached growth biological (nitrification), natural zeolites, or breakpoint chlorination; • Arsenic: iron addition/filtration, iron adsorption, or ion exchange; • Sulfate and TDS: attached growth biological or nanofiltration. Enhanced solar evaporation is an option for zero liquid discharge. For more information, contact Mark Reinsel at http:// apexengineering.us. n wateronline.com n Water Innovations 13 INORGANICCONTAMINANTS Mark Reinsel, Ph.D., PE, is president of Apex Engineering, PLLC. A process engineer with more than 30 years of experience in consulting, industry, and academia, Mark's recent work has focused on treating mining and other industrial wastewaters through chemical, physical, and biological methods. About The Author Figure 4. Jar testing Figure 3. Attached-growth media system

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