Many communities have obsolete infrastructure that represents an underutilized asset, often posing an environmental or safety hazard to the community. Terracon recently assisted one such community with a former municipal solid waste incinerator removal to allow repurposing of the building. Challenges on this project included the presence of hazardous ash impacting porous and non-porous surfaces, significantly limiting the recycling and reuse options for the non-porous (steel) components of the incinerator. To eliminate the exposure hazards and maximize the recycling potential to help control overall project costs, Terracon developed a cleaning and monitoring plan that allowed a large volume of the steel and other non-porous components to be recycled safely and effectively.
Terracon was contacted by a demolition contractor with whom we had completed previous demolition and cleaning projects at former incinerator sites. Our team developed a cleaning and management plan that was approved by the Minnesota Pollution Control Agency that allowed recycling of large volumes of metal materials. Terracon completed supplemental assessment for asbestos and cleaning validation to document the effectiveness of the cleaning process.
Cleaning was completed using high pressure washing, with wash water collected within the incinerator building. Terracon provided visual clearance of cleaned materials prior to off-site shipment for recycling. After cleaning was completed, the wash water and accumulated sediment required management and disposal.
Similar projects had utilized settling and/or bag filtration to remove heavy metal laden particulate from the wash water to below discharge limits of the local publicly owned treatment works (POTW). Initial settling and bag filtration tests on the water showed that zinc and cadmium concentrations were well above the applicable discharge limits of the POTW. Terracon’s industrial wastewater group was contacted to assess the situation and determine if treatment was feasible, bringing our experience with pre-treatment of heavy metal laden wastewater in industrial settings to bear on this field application.
A round of jar tests was conducted to determine if the metals were dissolved, chelated, or present as a fine particulate. The metals were determined to be dissolved but not chelated. A pH of 10.5 was selected for the initial treatment, which is between the minimum solubility pH point for zinc and cadmium, and would provide for precipitation of metals from the wash water. The pH was then adjusted prior to discharge in accordance with POTW requirements.
Significant safety considerations were discussed and mitigated due to the handling of strong acids and bases in the temporary system under bad weather conditions. Terracon conducted the on-site treatment in temperatures below zero degrees F. Initially, the pH of the water was adjusted to 10.5 with caustic using an air wand for mixing. The solution was allowed to settle and was pumped into a temporary batch treatment system. Two plastic, 1,000 gallon tanks were used to neutralize the water prior to discharge.
The water met metals and pH limits of the POTW and the treated batches were discharged to the sanitary sewer system. This treatment process was significantly less costly than other management options considered. The project was completed on schedule and on budget. Following the project, the demolition contractor’s supervisor made a point to call the Terracon department manager and thank him for the professional, efficient, and friendly service that had been provided on-site under difficult conditions.
Terracon is a provider of environmental, facilities, geotechnical, and materials testing services. This project is an example of the collaboration of multiple practice areas within the environmental service line to help our clients meet their regulatory, business, and community needs.
Mike Johnson, P.E., (Chemical Engineering) is an environmental department manager in our Minneapolis office. Mike has more than 25 years of experience in the industrial wastewater/environmental consulting industry. Mike leads our industrial services group which works on wastewater pre-treatment, air permitting, storm water management, remedial design, and regulatory compliance for clients across the country.
Ken Olson, P.G., Principal and Manager of the Minneapolis office has been providing environmental consulting services for more than 35 years. He has managed or supervised many hundreds of projects ranging from Phase I and Phase II investigations to CERCLA remedial investigations/feasibility studies/response action implementation.