Risk Analysis of Heavy Metal Accumulation from Sewage Sludge of Selected Wastewater Treatment Plants in Poland

Sewage sludge (SS) from wastewater treatment plants (WWTPs) has important soil-forming and fertilizing properties. However, it may not always be used for this purpose. One of the main reasons why SS cannot be used for natural purposes is its heavy metal (HM) content. SS from the wastewater treatment plant in Poland was subjected to an analysis of the potential anthropogenic hazard of HMs, especially in terms of their mobility and accumulation in soil. Calculations were made for the concentrations of HMs in SS from the analyzed wastewater treatment plants and in arable soil from measurement points in places of its potential use. The geoaccumulation index (GAI), potential environmental risk index (PERI), risk assessment code (RAC) and environmental risk determinant (ERD) were calculated. Then the values of the indicators were compared with the mobility of HMs, which was the highest risk of soil contamination. It was shown that a high level of potential risk and geoaccumulation indicators did not necessarily disqualify the use of SS, provided that HMs were in immovable fractions.