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Land application for multiple sewage plants

by Tom Chillemi

Applying treated wastewater to land would require an irrigation area of between 31 and 62 acres for a treatment plant with a capacity of 180,000 gallons per day (GPD), according to the executive summary of a study for the Hampton Roads Sanitation District (HRSD).

HRSD’s “land application” study is for a 180,000 GPD treatment plant.

Middlesex County has applied for a discharge permit for a 39,900 GPD treatment plant to serve the Middlesex Courthouse area and parts of Saluda.

As proposed, the Saluda treatment plant would discharge treated effluent into Urbanna Creek, and this is opposed by many citizens.

Recently, there have been discussions of connecting HRSD’s treatment plant in Urbanna and the treatment plant at the Middle Peninsula Regional Security Center (MPRSC) in Saluda with the proposed Saluda plant. The maximum daily flow is 100,000 GPD from the Urbanna plant, and 25,000 GPD from the jail.

If effluent were applied to a harvested forage crop such as hay, about 31 acres would be needed to take up a maximum of 1.5 inches of irrigation water per week, states the study. A forest area would need 62 acres to absorb the same 1.5 inches of water.

Another limiting factor is the number of pounds of nitrogen that can be taken up by plants per acre each year. The forage crop area could consume 529 pounds of nitrogen per acre each year. The forest would consume 225 pounds of nitrogen per acre annually.

State laws that go into effect in 2011 require removing more nutrients, such as nitrogen, from wastewater that is discharged into a body of water. Nutrient removal is very expensive and the Urbanna plant would need more than $3 million in improvements to meet the new requirements.

Nutrients that remain in wastewater feed algae in the receiving body of water and cause “algae blooms,” which restrict the amount of sunlight reaching the bottom. When the algae die, the decomposition uses up more oxygen in the water to the detriment of marine life.

In a land application system, nutrients are a fertilizer to be absorbed by the plants, which are also irrigated by the wastewater. The wastewater would be disinfected before spraying.

Because nutrients do not have to be removed when using land application, there is a cost savings as far as treatment is concerned. However, more land is needed.

Land area required for buffers and other features, such as storage lagoons, is not included in the primary irrigated area requirement.

Middlesex County has purchased about 30 acres a quarter mile east of the courthouse on which it proposes to build the conventional treatment plant.

The county has twice asked the State Water Control Board to postpone action on its treatment plant permit to give HRSD time to complete its land application study.

HRSD has no land application treatment plants at this time.

A private land application treatment plant in Remlik, about 3 miles west of Urbanna, has been operating for about 20 years and has a permit to treat 36,000 gallons per day.

posted 08.12.2009

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