Publication details
Effects of sewage sludge from Prague wastewater treatment plant on soil organisms
| Authors | |
|---|---|
| Year of publication | 2006 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | Sewage sludge is very rich in nutrients and organic matter. This makes the spreading of this kind of waste on land as a fertilizer or an organic soil improver very suitable. Unfortunately, the sludge tends to concentrate heavy metals and organic compounds present in waste waters. This hampers its reuse in agriculture and then landfilling as well as incineration is used despite their environmental drawbacks. The Sewage Sludge Directive (86/278/EEC) regulates sludge use in such way to prevent harmful effects on soil, vegetation, animals and man. Limit values for heavy metals are defined in sewage sludge for agricultural use. The directive is now under revision and limits for more chemicals (AOX, POPs, detergents) will be added. However, only chemical measures are not sufficient for proper risk assessment and toxicity testing should be added to sludge use regulation. In our study, we evaluated the possibility of routine testing of sludge ecotoxicity. The sewage sludge from the central wastewater treatment plant in Prague was used and it was found that only Zn a PAHs are slightly above the proposed limits. The sludge was sterilized, dried and finely ground (1 mm) and mixed with healthy agriculture soil with low content of organic matter in order to get increasing proportion of the sludge in the soil from 0.5 to 75%. Standard bioassays with Folsomia candida, Enchytraeus crypticus, Enchytraeus albidus and Caenorhabditis elegans were then performed. The effects on mortality were recorded for all species and none could survive above cca 50% sludge addition. The reproduction was much more sensitive with LC10 around 0.7 - 1.8% sludge addition. From these results, negligible risk may be expected because that percents correspond to cca 15 - 30 t/ha which is several times above an average sludge application rate. To conclude, the battery of soil bioassays was used without problems and we found it very suitable for sludge testing. |
| Related projects: |