关键词: 污染等级, 污染等级

Abstract: The paper aims to study sludge reduction in municipal wastewater treatment plant by bioleaching technology and ultimately achieve the purpose of resource utilization, and has practical significance. Three sequencing batches of bioleaching experiments were conducted in two local sewage treatment plants in Tianjin with a movable container testing machine. The results showed that under the condition of 15-25℃, 1.2 L/min of aeration rate and 72 h of reaction time, inputting 260 L initial inoculum and 0.73 kg nutrients into 400 L original mud, 3 batches of leaching experiments were conducted with reflux ratio of 40%. When the reaction time was 72 h, pH value of two kinds of sludge in 3 batches could be reduced from around 5 before leaching to 3 or less. Dissolution rates of cadmium, copper, zinc and nickel of both kinds of sludge reached more than 80% on average, of which, the dissolution rate of zinc and cadmium reached 94.26% and 86.67% . The average dissolution effect from high to low was as follows: zinc ＞ cadmium ＞ Cu＞ Ni. Mercury, lead and arsenic had the lowest average dissolution rate, which was 21.42%, 20.4% and 23.52%, respectively. After bioleaching solid-liquid separation, solid sludge moisture rate was 53% or less. Respectively adding 4 kg/t and 2 kg/t of lime to the liquid after condensation, ammonia, COD of sludge 1 and 2, and SS of sludge 1 exceeded pollutant emission standards in the upper part of the supernatant. Compared with the original mud, fecal coliform kill rate of bioleaching sludge was 99.99% . In the end of the bioleaching process, the total nutrient loss was 24.89% and 9.31% , respectively, and there was also certain loss of organic matters, while solid sludge salt content was more than 2.00%. Therefore, bioleaching technique had good application effect and prospect, and the study provided basis for further local engineering applications.