Diamond Chrome Plating is an industrial chrome plating facility that plates components for aircraft, military and industrial customers at a plant located in Howell, Mich. In 2007, the Michigan Department of Environmental Quality issued a permit that required storm water from the facility be monitored, controlled and treated if necessary. During the monitoring phase, elevated levels of total chromium, hexavalent chromium, cadmium and zinc were found.
What was needed was a cost-effective, easy-to-install, easy-to-maintain treatment system that would bring Diamond Chrome into compliance with the permit issued by the state of Michigan. The facility turned to American Peat Technology (APT) and its peat-based APTsorb ion exchange media to comply with the state permit.
APT had performed experimental work to evaluate the ability of APTsorb to remove trace metals from water in laboratory and small-scale field tests. APT’s data indicated that the media had a high affinity for trace metals. Staff at Diamond Chrome Plating conducted additional tests on site and decided to use APTsorb for full-scale treatment of the facility’s storm water.
The treatment system included two holding tanks and seven parallel treatment tanks. Storm water was initially collected in a 4,000-gal interceptor tank. As water accumulated, it was pumped to the treatment tanks at 150 gal per minute. As the storm water was pumped to the tanks, a small metering pump injected a ferrous sulfate solution to reduce chromium +6 to chromium +3. The water then entered a header that distributed the flow equally between the seven treatment tanks. Each 1,500-gal tank contained roughly 750 gal of APTsorb. A total of 12,000 lb of APTsorb was used in the system.
The APTsorb was particularly effective in removing total chromium and cadmium, with average removal efficiencies of 98.7 and 93.2%, respectively. Hexavalent chromium concentrations were generally below the detection limit of 5 ug/L. The hexavalent chromium and cadmium were below the permit limits. Treatment was successful for almost three years; concentrations began to increase in May 2011 and the media was replaced on Aug. 5, 2011.
The treatment system at Diamond Chrome operated successfully for three years with no flow problems and essentially no maintenance. The cost for the complete system was approximately $85,000 and was installed by Diamond Chrome staff. The APTsorb for this system cost about $15,000, which is equivalent to $5,000 per year.
When the removal capacity of the material had been exhausted, the material was easily removed from the treatment tanks with a vacuum truck and taken to a sanitary landfill. The disposal cost was $900 per ton. The cost of disposal for a wet sludge was significantly higher than for a drained and dry solid. However, the ease of removal and disposal outweighed the additional cost.
