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In Portsmouth, R.I., developers are moving full speed ahead at Freedom Bay, a residential development of luxury townhouses serving the burgeoning over-55 population. It is one of many such communities springing up across the country. Freedom Bay's approach to wastewater treatment, on the other hand, is not so common.
This planned development sits at the edge of protected wetlands that boast walking and hiking trails as well as nature preserves. The site of a former church and small school, the land previously featured an onsite water treatment plant. The developers who purchased the land almost 15 years ago retained the permit on the dormant facility, believing it might be needed one day. Portsmouth does not have public sewers, and there was no option to tie into the neighboring town's sewer system.
As plans began to take shape for Freedom Bay, the developers decided to reopen the onsite water treatment plant using updated technology. The Rhode Island Department of Environmental Protection (RIDEP) reviewed the initial plans for the new facility.
The RIDEP maintains very strict requirements for discharging effluent. The Freedom Bay site did not have soils that were suited for treated effluent disposal due to high water tables and slow percolation rates. There was an option to discharge the treated effluent in a stream that ultimately feeds into Narragansett Bay. Most municipalities that discharge into open bodies of water can take advantage of dilution credits. However, the stream in question runs dry for a portion of the year, leaving Freedom Bay with a permit containing very strict dissolved metal limits.
Jeff Marshall of Applied Water Management knew that to obtain the permits necessary to keep this project moving forward, the plant would need to incorporate membrane bioreactor (MBR) technology, in addition to the traditional activated sludge biological treatment processes. MBR would also work well with the reverse osmosis and ion exchange systems to remove all the dissolved metals as required by the permit.
MBR technology is growing in popularity because of its ability to meet the strict effluent quality guidelines dictated by various regulatory bodies. This biological treatment system utilizes a population of microorganisms to reduce the biological oxygen demand, total suspended solids and nitrogen.
Once the plant was permitted, the Freedom Bay project was given the green light to move forward. Part of the plan was to incorporate Kaeser Omega blower technology.
"We have historically used Kaeser Com-paK Plus units and recognize their value-added on a project like this one," Marshall said.
Just like in a traditional activated sludge plant, Kaeser's blowers serve to aerate the bacteria and organisms that are part of the biological process. In addition to providing aeration, these blowers also provide air to scour the membranes. At Freedom Bay, there are six Kaeser DB 130 Com-paK Plus tri-lobe blower units. Their space-saving design and extremely low pulsations have allowed them to be installed in piped parallel arrangements directly in the main building.
The effluent produced at Freedom Bay using Applied Water Management's complete system is actually cleaner than the water coming out of most household taps. With Phase I well underway, one more phase is planned to fill a lack of retirement housing in the area.