Municipal wastewater treatment plant sludge heavy metal pollution control methods?

Heavy metal pollution is the first problem to be solved for sludge reuse. Because heavy metals are difficult to migrate, easy to enrich and hazardous characteristics, become the most important constraints on the utilization of sludge for agricultural production. Studies have shown that the application of sludge can increase the heavy metal content in the edible part of soil and plants to different degrees, and then jeopardize the health of humans and animals through the food chain. The heavy metal content of sludge is similar in different regions, but it varies greatly. Usually, the heavy metal content in sludge produced mainly by treating domestic sewage is low, while the heavy metal content in sludge produced mainly by treating industrial wastewater is high. Industrial wastewater accounts for a large proportion of China's municipal wastewater, so heavy metal pollution has become the main limiting factor for agricultural utilization of sewage sludge.

Traditional treatment methods:

The traditional treatment method for heavy metal pollution in sludge is sludge composting, i.e., manually controlling the moisture, C/N value and ventilation conditions, and through microbial fermentation, the organic matter is transformed into the process of fertilizer. Sludge composting treatment in the sludge composition, composting conditions, etc. have a significant impact on the heavy metal form, leaching state heavy metal content decreased, the exchange state and the organic binding state heavy metal content increased, and residue state heavy metal content changes are also different, but than the total amount of other forms of heavy metals extracted from different leaching agents is much higher. Studies have shown that the composted sludge has a loose texture, the nutrients that can be utilized by plants increased, the cation exchange increased by 50%, and due to the dilution effect of the conditioner, the heavy metals were reduced by 7.3% to 16%, and the heavy metal content in the residual state was increased. 3% ~ 16%, and make the heavy metal form a big change. However, this method of external conditions (pH, temperature, O2 concentration, etc.) control is more stringent, and occupies a large area, long cycle, not for emergency sludge heavy metal pollution control.