Small-scale wastewater treatment facilities play an important role in improving the aquatic environment in many countries. Although sludge treatment is essential for overall wastewater treatment, it is difficult for small-scale facilities to use mechanical equipment or other facilities. As the first step of the sludge treatment, it is important to develop a convenient sludge thickening process for small-scale facilities. In this work, we examined the sludge thickening performance of a mesh filtration system: the mesh opening sizes of 100-500 microm, and the sludge (3,000-9,000 mg-SS/L) was obtained from a domestic wastewater treatment facility. The filtration was carried out only under the hydraulic pressure between the water level and the effluent port connected to the mesh filter module. The sludge reduction rates were in the range of 85-95% for 6-7 h; the initial filtration rate was very high, but the rate decreased with a decrease in hydraulic pressure due to the reduction of the water level in the vessel. In addition, the effluents (passed through the mesh) contained very low SS and could be directly discharged into the environment.

Oily sludge contains a large number of hydrocarbons, heavy metals, and other toxic and harmful substances, which not only pose a significant threat to human health but also severely impact the stability and sustainability of the ecological environment. Therefore, the development of a clean and efficient production process is urgently needed. The ozonation technology is a promising treatment method with high efficiency and no secondary pollution. In this study, ozonation technology was used to degrade the pollutants in the oily sludge, and the impact of different influencing factors on the treatment effect was discussed, and the operational parameters were optimized. Additionally, we investigated the mechanism of ozonation for oily sludge to provide a basis for a deeper understanding. The results demonstrated that after treatment, the total petroleum hydrocarbon content in the oily sludge was significantly reduced, and the residual oil rate decreased to 1.04 %, indicating the enormous potential of ozonation technology for oily sludge treatment.