environmental controls
WASTEWATER TREATMENT
BY THOMAS J. WEBER
WASTEWATER MANAGEMENT INC., CLEVELAND;
WMI-INC.COM/HOMEPAGE.JHTML
Today, some 15,000 companies in the United States perform electroplating andmetal finishing operations. These firms discharge their spent process wastewaterseither directly to rivers and streams, or indirectly to Publicly OwnedTreatment Works (POTWs). Metal finishing, by far, comprises more individualwastewater discharges than any other industrial category. Typically, pollutantscontained in metal finishing process waters are potentially hazardous, therefore,to comply with Clean Water Act requirements, the wastewaters must be treated,or contamination otherwise removed, before being discharged to waterways orPOTWs. Regulations, in general, require oxidation of cyanides, reduction ofhexavalent chromium, removal of heavy metals, and pH control.Understandably, for companies discharging wastewater directly to waterways(direct discharges), regulations promulgated through the years requireattainment of the more stringent concentration-based limitations for toxicwastewater constituents necessary for protection of aquatic life. These streamstandards were developed from Federal Water Quality Criteria and limit instreampollutant concentrations to levels that will not adversely affect drinkingwater quality and aquatic life. Since the mid 70s, state agencies have continuedto drive direct discharge limitations downward to levels well below waterquality-based stream standards, using antidegration, antibacksliding, andexisting effluent quality (EEQ) policies, and the number of direct dischargershas dropped precipitously. Implementation of biological-based criteria throughbiomonitoring and bioassay testing will continue to force direct dischargingfacility closures and relocation to POTWs.As the overwhelming majority of metal finishing companies are dischargingto POTWs, wastewater treatment systems for these firms are installed for compliancewith federal pretreatment standards, or...........
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مرجع : شرکت جلاپردازان پرشیا
