WETLAND DESIGN METHODS FOR RESIDENTIAL WASTEWATER TREATMENT¹

Abstract

Constructed wetlands have recently gained popularity as an alternative method for wastewater treatment. This paper compares two design methodologies currently used for constructed wetlands; Tennessee Valley Authority (TVA) and the Environmental Protection Agency (EPA) methods. A discussion of parameters for both methods is given and a wetland treatment system is designed for an individual residence with typical BOD5 loads and flow rates. Calculation results revealed significant discrepancies in the required constructed wetlands volume, and thus detention time, stemming from inherent differences in the design methodologies. The EPA method relies heavily on plug flow kinetics, and is therefore sensitive to changes in the reaction rate constant and media porosity. Conversely, TVA determines the surface area by sizing in accordance with a recommended hydraulic loading criterion and is affected only by the hydraulic flow rates. This study concluded that a constructed wetland is a viable option under design considerations that are not favorable for traditional on‐site wastewater treatment methods. However, it is recommended that conservative values for flow and loading rates be assumed to assure complete treatment for either of the design methods.

Restoring Nature, Without Mosquitoes?

“…“Insects” yielded two articles, neither of which addressed mosquitoes. Nor were mosquitoes mentioned in the seven articles (published since 1995) retrieved by searching “constructed wetland.” For six of the articles this makes sense, as they specifically addressed other aspects of wetlands, but one (Sauter & Leonard 1997) discussed wetland design methods for residential water treatment. In the introduction, the authors list several advantages, but no disadvantages, of using wetlands for treating wastewater.…”

“…The authors are aware that mosquitoes may be a problem, as in the discussion they write: “Because constructed wetlands are an above‐ground treatment method, their esthetic impact, both positive and negative, cannot be overlooked. For example, education of the community, or bordering neighbors, may be appropriate and advisable to help address concerns over odor or perceived vector problems before ground‐breaking” (Sauter & Leonard 1997: 162, emphasis added). We may wish mosquitoes were only a “perceived” problem, curable by “education.” Sometimes, though, educating neighbors will not be enough, for sometimes the problems they perceive are real.…”

Understanding the Role of Constructed Wetlands in Stormwater Management

“…Other pollutants comply with SEPP Limit the application, generation and migration of toxic substances to the maximum extent practicable 1 An example using SEPP (Waters of Victoria 1988), general surface waters segment. 2 SEPP Schedule F7-Yarra Catchment-urban waterways for the Yarra River main stream.…”

“…Whilst constructed wetlands have been utilized for some time in the treatment of wastewater, they only gained popularity for the treatment of stormwater runoff and flood protection in the last couple of decades [1,2]. Constructed wetlands are employed to remove sediment and nutrients, primarily phosphorus and nitrogen, from contaminated water [1].…”

Biosystem to purify wastewater from wet processing of coffee, district La Coipa, department Cajamarca, 2014

“…El valor Aν en filtros percoladores y biodis cos corresponde en su totalidad al área mojada, para el caso del biosistema acuáti co será la medida del área superficial de la porción de la vegetación y que está en con tacto con el agua residual. Por tanto, el valor de Aν será 15,7 m 2 /m 3 que es un valor reco mendado por Sauter and Leonard (1997). Dado que el área superficial del biosistema (As) es igual a (W)(L) se hace posible sustituir y reordenar la ecuación (1) para poder estimar el área requerida para el tratamiento biológico.…”