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CONVERSION OF A SMALL PACKAGE TREATMENT PLANT TO VEGETATED SUBMERGED-BED WETLAND SYSTEM
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 701P0104, . (doi: 10.13031/2013.15767)Authors: G.M. Powell, K.R Mankin
Keywords: constructed wetland, onsite wastewater treatment, rock-plant filter, submerged flow wetland, vegetated submerged bed, wastewater treatment
A package plant with a river discharge treated wastewater from a seasonal change
house/restroom facility at a Corps of Engineer's swimming beach in Kansas. This type of
treatment system was commonly used for small recreational areas. The treatment system
consisted of a small activated-sludge package plant with a duplex pump station and force main to
deliver effluent to the river below the dam outlet. Since it became operational in 1970, facility
management personnel experienced increasing operational difficulty, maintenance and repair
time, monitoring needs, and expenses for operation and repair. Long term, low maintenance and
low cost, solutions were desired. The package treatment system was converted to a septic tank.
A vegetated submerged-bed (VSB) wetland and chamber soil absorption system were added.
The conversion was made during May 1995 just prior to opening the swimming beach area. The
US Army, Corps of Engineers facility maintenance personnel completed the conversion in about
two weeks with weather delays and only minor difficulties.
Throughout nine seasons, the onsite system has operated with minor problems and minimal
expense. The facility manager is quite pleased with the results of this conversion. Monitoring of
the inlet and outlet flows of the VSB cell has confirmed excellent treatment performance by the
wetland component. A multi-parameter data logger was used to continuously evaluate system
performance before, during, and following the busy Independence Day holiday period. The
septic tank produced effluent concentrations as high as 40 mg/L NH4-N and 200 mg/L NO3-N
over the monitoring period, while effluent from the VSB cell never exceeded 4 mg/L NH4-N and
3 mg/L NO3-N. The conversion of small existing package plants to well engineered and well
constructed onsite wastewater systems appear to make good economic, environmental, and
management sense. Likewise, construction of new facilities using this technology also appears
to be a wise decision.