I did some work years ago promoting the sustainability of constructed wetlands for wastewater treatment, primarily for rural areas, although the approach can be used anywhere, eg, a constructed wetland treats all the waste water at Flagstaff’s Arboretum, and a large constructed wetland provides secondary treatment for a large city waste treatment plant in Phoenix. I think the best book on the subject (by a friend of mine, now semi-retired) is Constructed Wetlands in the Sustainable Landscape by Craig Campbell and Michael Ogden, available on Amazon.
I also designed / engineered a constructed wetland for a school in Lakeside, CA as a practicum project for my graduate studies in Conservation Ecology at NAU. The EPA also recommends constructed wetlands as the preferred waste water treatment approach for rural cities and areas where the city wants to provide economical sewage treatment to homes widely and thinly disbursed. The EPA has published a manual providing all the engineering and regulatory details. One of the benefits of city wastewater treatment by constructed wetlands (besides lower costs) is that preliminary studies show good results in reducing endocrine disrupting compounds through the action of water plant root absorption and photo remediation from sunshine. (see some references below) Also, several years ago a professor at NAU was doing some research on this issue. I don’t know the current status of this research, but could follow up.
One of the national luminaries in this area is John Todd, who passed away just this last August. You can find lots of great system design ideas in his writings and projects.
Hemming, J.H., W.T. Waller, M. Chow, N. Denslow, and B. Venables. 2001. Assessment of the efficacy of a constructed wetland to reduce or remove wastewater effluent toxicity and estrogenicity using biomarkers in fathead minnows (Pimephales promelas Rafinesque, 1820). Environ Toxicol and Chem. 20(10):2268:2275
Quinonez-Diaz MJ, Karpiscak MM, Ellman ED, Gerba CP., (Department of Soil, Water and Environmental Science, University of Arizona), Removal of pathogenic and indicator microorganisms by a constructed wetland receiving untreated domestic wastewater. J Environ Sci Health Part A Tox Hazard Subst Environ Eng. 2001;36(7):1311-20
Gray, James; Sedlak, David. Fate of estrogenic hormones in a constructed wetland with dense plant growth. Society of Environmental Toxicology and Chemistry, 24th Annual Meeting, November 13, 2003.
Chapman, H. 2003: Removal of endocrine disruptors by tertiary treatments and constructed wetlands in subtropical Australia. Water Science Technology, 47(9): 151-156.
Kolodziej E.P., Gray J.L. and Sedlak D.L. (2003) Quantification of steroid hormones with pheromonal properties in municipal wastewater effluent.Environmental Toxicology and Chemistry. 22, 2622-2629.