Water Treatment

Background

Foth, in conjunction with its construction joint venture partner, provided a groundwater collection and treatment facility at a former manufactured gas plant (MGP) site. The groundwater is heavily impacted by dense non-aqueous phase liquids (DNAPL), polycyclic aromatic hydrocarbon (PAHs), naphthalene, benzene, toluene ethylbenzene, and xylene (BTEX), and gas and diesel range organic (GRO/DRO) compounds.

Approach

The water treatment system consists of equalization, chemical de-emulsification, dissolved air flotation (DAF), multi-media filtration, organo clay adsorption, granular activated carbon (GAC) treatment and bag filtration. Sludge dewatering utilizes a plate and frame filter press. An ancillary system recovers free product (DNAPL) for offsite disposal.

The groundwater collection system includes 45 collection wells, a soil bentonite slurry wall and shoreline sheet pile wall. The majority of the groundwater collection system is in an area that will be restored to a public waterfront park. Startup and commissioning was on a tight timeframe because the subsequent related dredging phase was dependent on its completion.

The water treatment facility is nestled between a downtown business district, lakefront recreation area and residential neighborhood. The building and land architectural designs were developed to compliment the surrounding land uses and aesthetics.

Results

The system has been in operation since June 2016 and has consistently met extremely low discharge limits (total PAHs = 0.10 µg/L) required for direct discharge to a high quality surface water (Lake Superior).