Blackwater refers to the water and waste which are collected through fixtures such as toilets, urinals and bidets. It is possible to use this wastewater for non-drinking purposes once treated and disinfected. Given the current drought and water restrictions in Australia, blackwater recycling is being hailed by some as a revolution.
Conventional blackwater recycling uses air blowers to aerate the sewage to help cleanse it. Chlorine is then used to finish off the disinfection process. The Biolytix system claims to use 90 per cent less energy than other blackwater recycling systems, and with the potential to reduce greenhouse gases globally, the system describes itself as an ‘ecosystem in a tank’.
The product is an organic wet soil ecosystem in a tank and houses worms, beetles and billions of microscopic organisms. It recycles sewage and wastewater into clean irrigated water that can be used on the garden. It can also recycle all food scraps (with an in-sink grinder) and break down non-plastic sanitary items.
All water and sewage from the household is fed onto the Biolytix filter-bed using standard plumbing. The solids are broken down at this top filter layer and the remaining wastewater is then cleansed as it passes through the three other filter layers. After about 30 minutes, it’s clean and ready to use.
Dean Cameron, managing director at Biolytix, says: “The Biolytix system is powered by nature, not electricity. It emulates the genius of nature to harness the energy stored in sewage, including toilet paper, to nourish the organisms that convert the sewage into clean water. Biolytix is designed to be aerated by the organisms in it — therefore it does not rely on energy-guzzling air blowers like other conventional systems which often break down and need to be replaced.”
Other systems such as NovaClear, designed by water company EcoNova, recycle all typical household wastewater (both grey and black) to class A+ reusable water without the need for further disinfection, such as chlorine or UV. This is achieved with technology called MembraneSafe. Christian Uhrig, general manager and director, marketing and sales at EcoNova, says it works like human kidneys. “Wastewater passes through the membranes and contaminants are removed, resulting in safe water which is 99.9 per cent free of pathogens.” He says other benefits include water restriction free living, a chemical free process, low maintenance and a single compact tank which reduces freight and installation costs.
Enviroflow is another company offering a wastewater solution which is ecologically balanced. A company spokesman claims its sewage treatment systems “harness naturally occurring bacterial populations and sophisticated membrane technology to remove organic pollutants from wastewater, allowing safe discharge or reuse of the reclaimed wastewater”.
The application of recycled blackwater is determined by the treatment requirements, says Dr. Tony Taylor, chief scientific officer with the Australian Nuclear Science and Technology Organisation. “For sub-surface irrigation, primary and secondary treatment with disinfection of the water is required. Above-ground irrigation, wash down, laundry and toilet-flush purposes require class A water, which require primary, secondary and limited tertiary treatment, as well as disinfection,” he says.
The associated problems with recycling blackwater, according to Taylor, are potentially many and varied. “Influent can be a hazard and could include oil, caustic or other biocidal chemicals,” he says. Other problems can include the membrane filtration systems fouling or being cut by abrasives, the temperature being too low for culture to grow, large surges of volume or high nutrient loads, sensor system breakdowns and failures in pumps and scrapers.
Paul Downton, principal and urban ecologist at Ecopolis Architects, says blackwater recycling is becoming more commonplace in Australia, but despite more competitive pricing evident at the neighbourhood level, problems still relate to the disproportionate costs involved.
Taylor agrees. “Very few domestic recycling systems are accredited and in use. There are some decentralised systems that treat whole communities, but such systems are restricted to new property developments because retrofitting the double piping is expensive. There are a few small-scale sewer mines used to water parks, but they are still rare. The complexity of the systems, testing and maintenance costs are still prohibitive, so the economy of scale is important.”
In Ecopolis’ own blackwater recycling projects, Downton says the firm has used the Biolytix products on projects ranging from batch system composting toilets to individual dwellings in a cluster. “We have found the Biolytix products to be very flexible as a system that uses a biological, environmentally friendly process,” he says. It can also recycle blackwater and greywater in one system. Downton says any water recycling system for irrigation purposes involves high levels of testing and treatment, which can make putting them in smaller projects cost prohibitive.
Approvals are another issue, Downton says. “A few years ago we did a composting job for a rural council and there was a range of complaints about the process, which led to various appeals and ultimately set-backs for the project. For any system implementation, there will always be a lot of authorities that need to be involved on the approvals side of things.” Lesser issues, says Downton, may include the consideration of dual plumbing. But he says this is a design issue and not a barrier to installing the system.
The CRC (Co-operative Research Centre) has stated that although most systems are suitable for retro-fitting or re-engineering, the need to separate greywater from blackwater may limit application in existing houses built on slabs. However, the prevalence of existing Queenlander-style houses in South East Queensland makes the collection and re-use of individual household wastewater streams more feasible due to the ease of access to pipework. But treating greywater from the shower and laundry is a lot easier then treating blackwater, sewage or the nasty stuff that comes from the kitchen sink.
Blackwater recycling is often not an option if there is not sufficient space and if there is no room inside or in areas that freeze in winter. There are also health issues to be considered. If systems are not properly maintained, the water quality can deteriorate, making the probability of diseases such as gastroenteritis, giardiasis and cryptosporidiosis a serious threat.
“Effective disinfection, filtration, monitoring systems and regular scheduled maintenance checks should prevent the occurrence of water-borne diseases,” Taylor says. “This is why the accreditation requirements for such systems are very stringent. The value of public health is greater than the value of a pretty garden.”
Overall, the largest barriers to overcome are public health issues, retrofitting systems, economy of scale and the ‘yuck factor’. Taylor says: “These problems can be minimised by the co-ordination of town planning with health and environment authorities, subsidising the accreditation of recycling systems, research, research, research and public education.”
