Harm of Sludge
1. It smells bad. Many perishable organic compounds volatilize in sludge treatment, transportation and storage to emit a variety of odors, affecting the environment.
2. High risk. Sludge contains a large number of viruses, bacteria, protozoa, high concentrations of zinc, copper, chromium, lead, cadmium and other heavy metals, toxic organic compounds, etc., which pose a serious potential threat to water resources and human health. In the process of sewage treatment, bacteria and most parasitic organisms remain in the sludge. Viruses can be adsorbed on the particles in the sewage and deposited into the sludge with the precipitation of particles. The number of pathogenic bacteria in raw sludge is billions per gram. These microorganisms include: Escherichia coli, E. coli, Streptococcus faecalis, bacteriophages, Salmonella, dysentery, Trichoderma aeruginosa, parasite eggs/larvae, ascaris, whipworm, colony whipworm, Toxoplasma, Hymenoptera larvae, enterovirus, etc. Because the sources of municipal sewage are human living environment, coliform bacteria, coliform fecal bacteria, Streptococcus faecalis and so on, which are the normal excreta of mammalian rectum, their quantity is basically constant in sewage and sludge. The proportion of other pathogens such as salmonella, dysentery, enteroviruses (e.g. poliovirus, coxsackievirus, hepatitis virus, rotavirus) and parasites (e.g. ascaris, whipworm and entamoeba) in sewage/sludge is related to the prevalence of local infectious diseases. Obviously, if the sludge after mechanical dewatering is not properly disposed of and enters the human food chain, it will inevitably lead to the spread of disease.
Common types of sludge: 1. domestic sludge; 2. printing and dyeing sludge; 3. paper sludge; 4. tannery sludge; 5. electroplating sludge; 6. petrochemical sludge.
Target and Task of Sludge Treatment
The main objectives and tasks of sludge treatment are as follows: firstly, reducing water content to create conditions for subsequent treatment, utilization and transportation; secondly, eliminating toxic and harmful substances that affect the polluted environment; and thirdly, recovering energy and resources. To sum up, it is: stability; harmlessness; reduction; resourcefulness.