III. Heavy metal content of sewage effluent, sludge, soil, and pasture

Publisher Website
Google Scholar
Abstract
Surface irrigation of pasture with treated sewage effluent at Templeton, Christchurch [New Zealand] for 16 yr, had little effect on the heavy metal composition of the soil or pasture. Slightly higher levels of 0.1N HC1-extractable Zn, Cu, Co and Mn in the effluent-treated soil did not increase levels of these elements in the pasture, and did not increase the Cd/Zn ratio. The absence of any marked changes in heavy metal content is attributed to the lowlevels of these elements in the raw sewage effluent, which is of domestic origin. At the present effluent application rate (840 mm/yr) the scheme, without sludge disposal, has an essentially idefinite life span, in terms of heavy metal accumulation. If land application of the sludge is introduced, it would take at least 200 yr for heavy metals to reach the recommended limit of 5% of the soil cation exchange capacity.