analysis of a pilot-scale anaerobic baffled reactor treating domestic ...

million toilets was required in the intervening years (Hendriks, 2007). South Africa is committed to
eradicating its water supply and sanitation backlogs by 2008 and 2010 respectively, both in keeping
with (and in fact exceeding) the requirements of the Millennium Development Goals, and in the
upholding of the South African constitution, which states that ...Everyone has the right - to … an
environment that is not harmful to their health or well-being;…Everyone has the right to have access
to - … sufficient food and water.
The primary function of a sanitation system is to create a physical barrier between humans and human
excrement to prevent the transmission of pathogens via the faecal-oral route (Goldstein, 1999). In
densely populated communities, a further and equally important objective is to prevent contamination
of the environment with large amounts of pollutants including organics, nitrogen and phosphorus,
which lead to eutrophication of water resources and disruption of natural eco-systems. Water-borne
sanitation where diluted toilet contents are collected and transported to an activated sludge treatment
system is a high-technology solution, however, it has large infrastructural, operational, maintenance
and environmental costs which are economically, environmentally and socially unsustainable in many
communities (Rockstrom et al., 2005; Foxon et al., 2006). In a South African context, the provision of
waterborne sanitation systems, and full pressure water supply required for the operation thereof, is
unsustainable in terms of the availability and cost of the water and infrastructure required for a
universal waterborne sanitation system, the necessary financial resources, and the human capacity to
operate and maintain these systems on a continuous basis (Hanekom, 2006). On an international level,
there is an increasing realisation that, particularly in water-scarce and arid countries, the
implementation of centralised wastewater treatment facilities supplied by a comprehensive sewer
system through which wastes are transported by large volumes of drinking water is illogical and
environmentally unsound (van Lier and Lettinga, 1999).
There is thus both a national and international drive to provide sustainable alternative water and
sanitation services to millions of South Africans in the course of this decade, and an unsurpassed
opportunity for innovation in the sanitation sector.
1.2 THE ANAEROBIC BAFFLED REACTOR PROJECT
The motivation for this project was that, in certain instances, communities may be supplied with piped
potable water, but be located geographically in such a way that sewerage could not be removed by
trunk sewer to central wastewater treatment facilities. Because of the cost of water to low-income
householders, household water usage may be low and therefore the wastewater produced from these
areas may be concentrated. It was proposed that research should be undertaken to identify potential
decentralised waterborne wastewater treatment technologies that could function within this context
(Foxon et al., 2006).
Anaerobic digestion is an area of biotechnology that is growing at a rapid rate. For many waste
treatment applications it is becoming the technology of choice through its ability to produce renewable
energy in the form of biogas, by reduction of greenhouse gases produced by other treatment processes
and by the use of non-renewable fuels that biogas can replace; and by diverting organic waste from
landfill and incineration (DEFRA, 2007).
Anaerobic digestion is a reasonable choice of bioprocess for on-site and decentralised sanitation since
energy is not required for aeration and most importantly because of the low excess sludge production
2