The greywater pipeline
Sampling soils under a greywater application site onto a household lawn.
Grey water is household water from kitchen sinks, dishwashers, washing machines, showers, baths, and basins. As such, it contains a complex mixture of chemicals used in household products, such as surfactants, detergents, bleaches, dyes, enzymes, fragrances, flavourings, preservatives, oils and greases, and antimicrobials.
CBIR scientists are currently researching the environmental effects of some of the chemicals found in greywater. One potential effect of these chemicals is the loss of soil structure, which can lead to soil compaction and surface sealing. Another effect is the contamination of waterways. Phosphate, for example, while beneficial for lawn growth, becomes a pollutant in waterways, causing increased algal growth.
Scientists have paid particular attention to chemicals such as triclosan, an anti-microbial compound found in soaps, toothpastes, deodorant, and other personal care products, bisphenol-A, a plasticiser, and the pharmaceutical, carbamazepine. Triclosan can have toxilogical effects on soil organisms, particularly on earthworms and springtails. Antimicrobials, also found in greywater, are another environmental issue currently being addressed.
Antimicrobials kill both pathogen and beneficial microbes in soils, which can have adverse effects on microbial processes such as the decomposition of plant litter. Furthermore, enzymes in greywater can also upset the natural enzyme balance in soils.
Several new technologies are available that help scientists analyse the effects of contaminants on soil properties. For example, ESR, Landcare Research, Plant & Food Research, and Northcott Consultants are conducting lysimeter experiments to investigate the change in soil properties caused by zinc and copper in combination with tricolsan. Soil analyses conducted by Scion, Cawthron Institute, ESR, and Landcare Research are comparing the effects of applying biosolids on soil properties and on tree growth in pine plantations. To examine the overall effects on soil properties and the growth of native plants, Scion scientists are also applying different vermicasted and non-vermicasted mixtures of biowastes to degraded pumice soils.
Craig Ross — Landcare Research