Ashfield, MA Solar-Aquatic® Wastewater Treatment Plant
Type: Policy
Status: Established in 1996
Source File: http://www.mwpca.org/ashfield.htm
Description:
This is the first municipal Solar-Aquatic® Wastewater Treatment Plant in the Commonwealth. The AWWTP serves the village of Ashfield in the Berkshire hills, about midway between Northampton and Greenfield on Route 116. There are currently about 165 household equivalents connected. Out design flow is 25,000 gpd, some of which is seasonal. The process is advanced tertiary treatment. Our permit levels include 30 mg/l BOD, 30 Mg/l TSS and 10 mg/l total nitrogen.
Our implementation of the Solar-Aquatic® process consists of about 10,500 square feet of greenhouse space, plus an administrative building. Municipal sewage flows in through a bar-rack and sodium bicarbonate is added to supplement the naturally low alkalinity. After an average retention time of less than a day in a preliminary conditioning tank, the flow is metered to a splitter and into six rows of solar tanks, eight tanks in each row. Each tank is about 1,000 gallons, and is constructed as a pond with transparent walls. A variety of emergent plants grow in these tanks, along with snails, fish, and numerous microorganisms. A bubbler in each tank keeps the room odor free and the animals healthy. After solar tank treatment, the flow moves to a clarifier where settleable solids are recycled or wasted. To date, we have produced about 0.25% waste sludge at 1.8% solids, which is trucked offsite for disposal.
The flow continues through a sand filter and then to a constructed wetland, or the "Marsh Greenhouse" for denitrification. The marsh is 5000 square feet of 4-1/2 feet deep crushed stone through which the water flows with a two to three day retention time. The addition of methanol encourages bacterial growth which effects denitrification to below 1 ppm. Final disinfection is by ultra-violet irradiation. The flow is measured and then goes to a leaching field through a dosing chamber.
As an extra option, we have arranged the marsh in true jungle fashion, with banana trees, flowers, a parrot flying free, numerous turtles, fountains and even a daily monsoon, complete with sound effects. It is not your average wastewater treatment plant.