The Research And Assessment Of Environmental Effect On Preparation Of Ceramsite Using The Chromium-Containing Tannery Sludge

Tannery wastewater produces tannery sludge containing a large amount of organic pollutants and chromium during the process of biochemical treatment,which causes potential harm to the environment.In this project,the chromium-containing tannery sludge will be made ceramsites through the rotary kiln incineration system by fly ash and clay.More important the products of ceramsites have the characteristics of light weight,high strength,and low water absorption.The results indicate that the recycling of chromium-containing tannery sludge resources will provide a new method for tanning treatment and will reduce the environmental damage of leather containing chromium.Firstly,the chemical composition of the chromium-containing tannery sludge,fly ash and clay in leather tanning was investigated.The physicochemical properties and chromium content in the chromium-containing tannery sludge were analyzed.The results were shown that the contents of SiO2 and Al2O3 were relatively low,while the contents of these two types of materials in fly ash and clay were relatively high,When adjusting,so the ratio of raw materials for ceramsites will be adjusted to control the content of SiO2 and Al2O3 which will promote granulation and strength of the ceramsites.Secondly,the ceramsites were prepared using ceramics containing chromium-containing tannery sludge,fly ash and clay as raw material.Different factors such as the ratio of raw materials,sintering temperature,and sintering time were applied to assess the cylinder compressive strength,bulk density,and water absorption of the ceramsites.The effects of various properties such as quality and leaching amount of chromium were also investigated.The results were shown that:different raw material ratios,sintering temperature and sintering time affected the cylindrical drum compressive strength,bulk density,water absorption and chromium leaching significantly.The optimum process parameters for preparing ceramsites were as follows:the ratio of raw materials to the chromium-containing tannery sludge:fly ash:clay = 5:3:2,the suitable sintering temperature was 1150?,and the suitable sintering time was 30 min.Finally,the waste gas,waste water,noise and solid waste of the kiln incineration system were determined to assess the environmental safety.The results were shown that:1.The emission concentrations of exhaust gas pollutants from the rotary kiln incineration system can all meet the criterion of "Environmental Protection Technical Specifications for Pollution Control of Hazardous Wastes"(GB18484-2001)and"Technical Code for Environmental Protection of Chromium Slag Pollution(Interim)Table 2 Limiting requirements for air pollutant control indicators for chromium slag facilities "(HJ/T301-2007).2.The concentration of chromium after treatment in the secondary treatment system for flue gas treatment can reach the standard limit value of Table 1 in the Integrated Wastewater Discharge Standard(GB8978-1996)at the monitoring point(pretreatment facility exit).3.The noise value day-time and night-time at boundary can all meet the standard limit value in "Emission standard for industrial enterprises noise at boundary"(GB 12348-2008).