Where there's muck, there's value
They find it intriguing that two nice women are willing to get in amongst "their sewage" to take samples. Not that they are in any doubt about the importance of this sample taking -- which forms an important component of the scientific research of Dr Gibbs and Ms Hu, and plays an important role in reducing the risk to public health when types of sewage are handled or recycled. "Raw sludge (the settled part of sewage) can look pretty awful," admits Dr Gibbs. "Anything and everything ends up in the sludge, from hairs to seeds to bits of plastic.""But apart from making interesting party conversation it's not as bad as it sounds."Dr Gibbs' work is far more than just party conversation, however. Together with a group of associates, Professor Goen Ho, Jatinder Sidhu, Debra McGrath and Catherine Hu, Dr Gibbs is braving the human waste at the Water Corporation to determine just how to use it safely. In particular she is researching the safe use of biosolids (solids which are mainly organic material after sewage has been stabilised).And why is that important? Well, if the thought of poking sample test tubes into human solids wrinkles your nose, how would you feel about it being spread all over your garden vegetables or your lovely azaleas?It might be common to use animal fertiliser but human manure is another matter -- human faeces contain pathogens that cause diseases in humans.At the moment, broad acre crop farmers in Western Australia use biosolids on their crops because such produce is grown above ground and is processed before consumption. The biosolids have also been treated to a certain extent. The practice of using biosolids on broad acre crops is a fairly common practice worldwide.
However, market gardeners are banned from using untreated biosolids because their fruit and vegetables are eaten raw, and a sufficient witholding period is not practicable.You may, however, find biosolids in the compost you buy from your local nursery. Here is where Dr Gibbs and her associates from Murdoch University's Institute for Environmental Science come in.Under a project sponsored by the Water Corporation, they are trying to determine if the concentration and viability (whether the pathogens are alive or not) of pathogens in biosolids make it safe enough to allow it to be used as compost material.The research is important to the Water Corporation because it is an environmentally aware organisation that is looking for the safest and most efficient way of dealing with biosolids, said Dr GibbsUsing biosolids as compost would be a better solution than other methods of disposing biosolids that are commonly used overseas and in the eastern states.Most treatment plants separate the liquid wastewater from the sludge component and dispose of the treated liquid effluent in the ocean while the biosolids are incinerated, stored or landfilled.But incineration is an expensive process which also impacts negatively on the environment. And landfill sites are becoming difficult to find.Using biosolids as compost would be a better alternative."It's a much more environmentally sustainable solution," said Dr Gibbs. "It is treating biosolids as a resource that can be recycled in an environmentally friendly way, rather than as a waste product to be disposed of."But is it safe?Previous research has shown biosolids contains Cryptosporidium, Salmonella, E.coli and other little "nasties" that can make you sick. Giardia was found to be the most prevalent pathogen in biosolids.Dr Gibbs and her team are investigating the concentration and viability of Giardia in biosolids.The project will employ flow cytometry, a technique used to separate Giardia from the biosolids.Dr Gibbs will also use fluorescent in situ hybridisation (F.I.S.H.), a technique used to detect the presence of ribosomal RNA -- an indicator that cells are viable and alive.It is a relatively new technology although it has already been successfully used for detecting the viability of Cryptosporidum -- a pathogen related to Giardia.If the research finds that there are high enough concentrations of viable Giardia in biosolids to make it unsafe, it may be that treatment needs to be modified before it can be used as compost. Different management techniques for biosolids may need to be implemented to ensure public health is protected.Dr Gibbs said the research would be valuable in providing an environmentally friendly solution to waste disposal."At the moment there are high costs involved in wastewater treatment and the costs are going to keep going up unless reasonable and safe alternatives are found for the use of biosolids." |
| Catherine Hu takes a sample from a mound of sludge. |
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Dr Robyn Gibbs School of Environmental Science Telephone (08) 9360 2385 email gibbs@essun1.murdoch.edu.au |