Removal of Heavy Metals from Sewage Sludge by Using Humic Substances

The paper discusses the issue of extracting heavy metals from domestic wastewater sludge as fertilizers for agricultural purposes. Currently, the bulk of the formed precipitation is not utilized due to the presence of toxic chemicals in their composition, mainly heavy metals. This is due to the fact that industrial wastewater enters the city sewer network after insufficient treatment. Based on the foregoing, the development of progressive technologies and methods for removing heavy metals from urban wastewater sludge is an extremely urgent and timely task, the successful solution of which will significantly reduce the level of negative impact of this sludge on the environment. A technological scheme for the extraction of heavy metals from domestic wastewater sludge has been developed; the optimal modes of the technological process are given. It has been established that it is advisable to use organic flocculants to intensify the processes of thickening and dehydration of urban wastewater sludge. The most effective are cationic flocculants. Their use intensifies the process of sludge dewatering both in sludge beds and in mechanical dewatering devices – filter presses and centrifuges.