Heavy Metals and Organics in Domestic Wastewater

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Report no. UWRAA 79

July 1994

Synopsis

This survey of heavy metals and organics in domestic sewage was carried out in the Adelaide metropolitan area in 1992-93 in order to determine the pollution load relative to that of Commerce and Industry. Surveys of four households and four wet wells were undertaken.

The results indicate that the metals with significant loadings are copper, aluminium and zinc. At least half of the copper comes from the household plumbing whilst a similar proportion of the aluminium is in the water supply entering the households. Most of the zinc is from the bathroom. Boron loading is significant and is a component of both bathroom and laundry wastewater.

Organic and TDS loadings in household discharges were generally proportional to the volume of water used in each area, with more TDS (Total Dissolved Solids) and suspended solids discharged from the laundry than from the bathroom. Although the kitchen had high concentrations of organics, the low volume gave a lower overall load. The overall organic load structure from household sampling was incomplete, however, as the household samples did not include the toilet wastes, the wet wells consequently gave better data for comparison with the loadings on treatment works.

Phosphorus loadings from households were significant, exceeding the highest metal load by at least a factor of ten. The levels of phosphorus in some household laundry samples were almost twice that recommended in the AWRC guidelines for discharges to sewers. Even where there was a significant industrial input, the household load was some 50 percent of the total.

The phosphorus load pattern requires further clarification but it is the pollutant most obviously a target for load reduction. Aluminium and copper loads are not due to household activities but zinc and possibly boron loads might be targeted for reduction.

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