Infrastructure Models for Ecological Wastewater Management - Restorative Redevelopment of Devastated Ecocultural Landscapes - page 405

d eveloPment of n eW e CoteChnology
Subsurface-flow wetland technology was initially developed in Germany in the 1950s
(Börner et al. 1998) and has spread worldwide, with increasing use and interest over
the last 25 years (IWA Specialist Group 2000; Kadlec and Knight 1996; Steiner and
Watson 1993; EPA 2000; Wallace and Knight 2006).
Single-home subsurface-flow wetland systems are the most widely adopted form
of ecotechnology in the world (Wallace and Knight 2004). There are estimated to
be over fifty thousand systems worldwide (Kadlec 2004). A typical subsurface-flow
constructed wetland is shown in Figure 20.3.
Subsurface-flow constructed wetland treatment systems are compact, provide
effective treatment of pathogens, and do not expose wastewater during the treatment
process. They are capable of producing effluents that meet World Health Organization
(WHO; 1989) reuse guidelines, and up-to-date design criteria are readily available
(Wallace and Knight 2006). Because these wetlands can be constructed with local
materials and labor (often by the homeowners themselves), they have become very
popular in some developing areas. A typical small-scale subsurface-flow wetland
system is shown in Figure 20.4.

W ater as a C arrier m ediUm
In the initial stage of technology development, wetlands were used in relatively water-
rich regions of Europe and North America. In many developing countries, water is
not available in sufficient quantity (or it is too expensive) to be used in conventional
flush toilets. Instead, pit latrines, pour-flush toilets, or composting toilet systems may
provide for more effective management of fecal material. This does not necessarily
preclude ecological wastewater management, as indicated in Figure 20.5.
In the absence of conventional flush toilets, separation of fecal material (black-
water) and graywater (urine) is commonly employed. Because graywater-urine is

Influent distribution
pipes

Emergent vegetation

Water level

Influent

Water level
control

Flow

Euent

Coarse media
Main bed media

Impermeable liner

FIGURE 20.3 Schematic of a subsurface-flow wetland. Reprinted with permission from
Wallace, S. D., and R. L. Knight. 2006. Feasibility, design criteria, and O&M require-
ments for small-scale constructed wetland wastewater treatment systems. Project 01-CTS-5.
Alexandria, Virginia: Water Environment Research Foundation.