Archive for April, 2010

Constructed wetlands for sewage treatment

April 25, 2010
For ecological or spatial purposes there are some sites which will best be served by a reduced footprint soil absorption area.  This requires pretreatment of the sewage to reduce organic loading.

Many systems are available in Virginia to reduce the organic load, some such as the Ecopure use a peat matrix to filter and absorb soluble organics so that microbes are able to consume the food sources and cleanse the effluent, other systems provide similar benefits ith active treatment. For example the FAST system creates an aerobic treatment environment via pumps and environmental controls allowing for biological process to consume the organic wastes. The FAST will cost ca. $7-8k plus support and installation. It does a very good job, though it requires maintainance, which must be contracted with an approved service provider. The Advantex also uses pumps and controls to distribute the waste constituents across a fabric media suspended on racks for aeration.

Many of these systems requires electricity, and may require adjustments, occasionally you will get a plume of moist air which can be odiferous, if you’ve been to the Tavern the stack in the parking lot is off a FAST, though with a much higher load due to the kitchen.

A constructed wetland (CW)will be competitive in cost, and if well thought out (read designed & sited) will have a positive impact. Picture green foliage and bright seasonal flowers, gentle berms, perhaps a low fence to keep out kids or domestic animals; minimal maintainance which I believe is similar to gardening ie. mow annually, check weirs, sample once a year for an interim period. The wetland does it’s work silently, there is a short anaerobic zone which will be in dynamic equilibrium with the aerobic margins, tis is the root zone, and the PE’s job crosses with the naturalists in picking wetland vegetation. These include flowering plants, refer to the pages I provided you from the text Wastewater Treatment in Constructed Wetlands with Horizontal Sub-Surface Flow. This is an exciting and well understood technology in Europe, and I would hope that your incorporation in a residential cluster will prove the concept and lead to it’s incorporation in later phases.

Wastewater Treatment in Constructed Wetlands with Horizontal Sub-Surface Flow
Under the Department of Health Regulations a constructed wetland must be designed and installed under the supervision of a Professional Engineer (PE).
There are several permitted CW’s in Pulaski, one in McCoy, Bedford; at least one in Floyd though I don’t think it’s been built yet, though I consulted on several here, one intended for multi family use, and there was another approved but not constructed in the western part of the County. There are quite a few larger CWs, including systems that were constructed to serve trailer parks and small communities.
I’m sure that seeing will be believing, and it is in your interest to consider this technology; I would be pleased to advise you about the utility of a CW for your project.