NEB’s headquarters in Ipswich, MA was designed to minimize its environmental impact. As part of the plan to build a more environmentally sound facility, NEB chose an innovative method to treat wastewater, rather than use conventional sewerage. All of NEB’s wastewater is treated on-site using a Solar Aquatics® Wastewater Treatment System that is capable of treating up to 27,500 gallons per day. Housed in a beautiful greenhouse abound with tropical plants, the system utilizes and accelerates the processes found in streams and wetlands to purify the water to tertiary standards.

Tropical plants growing inside the greenhouse of the Solar Aquatics Wastewater Treatment have a key role in the water treatment process.

The water treatment process combines proven wastewater treatment practices with the biological components of ecologies found in nature. Water first enters an in-ground blending tank, where it is aerated and bioaugmented with microorganisms that have been recycled from the clarification process described below. The aerobic biological breakdown of organic matter begins here; compounds such as fats, starches and proteins are converted to carbon dioxide and simpler matter that can be utilized by organisms downstream.

The water continues into the greenhouse where it enters several six foot tall translucent tanks. These tanks host a variety of vegetation which provide a habitat for bacteria, zooplankton, snails, and other organisms, while algae grow on the tank walls. This ecosystem works in unison to metabolize nutrients and further break down and remove wastes. Autotrophic bacteria nitrify ammonia by oxidizing it into nitrate while algae and plants directly metabolize nitrate, ammonia and soluble orthophosphates. The bacteria are consumed by rotifers while snails, zooplankton, and worms begin the process of sludge digestion.

Next is the clarification process, where the suspended biological solids are allowed to settle. The biologically rich sediment that forms in the clarifier is recycled back to bioaugment the incoming wastewater stream in the blending tank. Water leaving the clarifier is clear in appearance but still contains microbes and certain nutrients (including nitrates). After clarification, any remaining solids are removed by a sand filter.

Following filtration, water enters the self-contained subsurface flow wetlands, where denitrification is achieved in anoxic conditions. Nitrate is reduced by facultative heterotrophic bacteria to nitrogen gas, hydroxide, and water in the presence of an electron donor. Certain pathogenic bacteria are destroyed by the action of wetland plants and further nutrient removal is achieved. To keep the wetland biology flourishing, approximately 50 percent of the water that flows to the end is returned back to the beginning of the wetland for bioaugmentation.

The final treatment step is disinfection. Ultraviolet light is used to kill or denature bacteria and viruses safely without the use of chemicals such as chlorine. The tertiary quality water meets stringent requirements, making it clean enough for water reuse or groundwater recharge. NEB discharges this high quality water for the purpose of groundwater recharge; a great option given its locality to the Ipswich River*.

* The Ipswich River, with 45 tributaries, has a 155 square mile watershed and was named one of the 10 most endangered rivers in America due to repeated low-flow and no-flow periods.

(Article by Andrew Posner, JTED, Inc.)