BIOSOLIDS/PRETREATMENT SUCCESS STORY IN MERRIMACK, NEW HAMPSHIRE

The Merrimack Wastewater Treatment Facility, the first secondary wastewater treatment plant constructed along the Merrimack River, began operations in May 1970. The wastewater treatment plant was designed to treat wastewater from a large brewery, as well as other industrial, and commercial wastestreams. In the late seventies, Merrimack began a pilot program to compost its sludge. By March 1982, Merrimack ceased utilizing its incinerator and relied solely on composting to manage the tons of sludge the plant produces annually. In 1994, Merrimack constructed a 15 bay in-vessel composting facility to improve the marketability of its product. It is the largest compost facility of its type in northern New England.Concurrently, with the development of Merrimack's beneficial use of sludge strategy, the wastewater treatment plant developed and implemented a pretreatment program to control and monitor industrial discharges. Merrimack utilizes a results-oriented pretreatment program where metal and pollutant loadings in the facility's influent, effluent, and compost are monitored regularly. Merrimack also works proactively with the industry it serves to seek collaborative solutions to reduce pollutants from industry's discharge, and subsequently, the plants influent. For instance, several industries were utilizing a molybdenum-based chemical for corrosion control in their cooling towers. We recommended that they consider using an alternative. As a result, our molybdenum loadings were reduced in our treatment plant influent and compost. In fact, we have deferred establishing a local limit due to the relative low concentrations found in our plant influent.Merrimack has made a significant investment in establishing a successful composting program. First, we have worked with our industrial base to assure that our plant's influent is consistent with the strict environmental requirements that compost must meet. Second, we have made the capital investment to assure that our product is of the highest quality to meet market demands.