Synergism of uncoupler dicoumarin and nonmetallic mineral tourmaline for the sewage sludge treatment process: Reducing sludge generation
Jun Li, Salma Tabassum
Abstract
Environmental concerns linked to the recycling of sewage sludge on land involve the hazard of nutrient leaching, impacts on soil biodiversity and greenhouse gas emissions. Sludge reduction in a wastewater treatment plant has recently received considerable attention worldwide. Large amounts of excess sludge needs to be disposed of in a cost-effective and environmentally friendly manner. In this study, dicoumarin was used as a metabolic uncoupler, its effect on the sludge reduction, effluent quality and sludge performance at the low concentration range (≤10 mg/L) and at high concentration (40 mg/L) in the sequencing batch reactor (SBR) system was investigated. It showed that Yobs was decreased with high dicoumarin concentration. Chemical oxygen demand (COD) and total nitrogen (TN) removal efficiency are also decreased while the sludge activity was enhanced. Tourmaline, a low cost natural nonmetallic mineral with unique physical properties and a promising environmental material could improve the negative effects caused by high concentration of dicoumarin without increasing the sludge yield in the SBR system. Synergistic effect of tourmaline with high concentration dicoumarin showed COD and TN removal efficiency increase. Yobs value was 0.13. The decrease in nitrite accumulation and increase in microbial activity may correlate to the existence of electrostatic fields and far infrared rays generated by tourmaline. Tourmaline also improved the sludge settling performance due to its adsorption characteristics. Effect of optimum environmental conditions; pH (6.5 ± 0.3, 7.5 ± 0.3, and 8.5 ± 0.3), temperature (15 °C, 25 °C, and 35 °C) and other factors on the synergistic action of dicoumarin and tourmaline was also studied. It is recommended to use dicoumarin as the main component and tourmaline as the auxiliary component. The synergistic effect of the two can solve the negative impact caused by the uncoupling agent administration alone.