Study On The Quality And Resource Utilization Of Hot Alkali Pretreatment Sludge

A large amount of sludge can be produced during biological wastewater treatment processes in the urban sewage plant which is rich in organic matters,it has the potential of resource utilization.The pretreatment of sewage sludge,preparation and adsorption characteristics of sludge bio-char were studied in order to realize the separate reclamation and reuse of sewage sludge and improve the utilize efficiency of sludge resources.In this paper,the sewage sludge was collected from QingHe sewage plant in Beijing and response surface methodology was used to find the best technological parameters of sludge thermal-alkaline pretreatment.Research results show that temperature,time and pH value were the three key factors and the optimal technological parameters of sludge thermal-alkaline pretreatment were 175.6 ?,pH value 13.0 and 1.2h.When the concentration of sludge is 9.7±0.2 g·L-1(VSS),405.75 mg·g VSS-1 of soluble protein can be dissolved and the dissolution rate of protein is 66.12%.The supernatant of thermal-alkaline pretreated sludge has the potential of anaerobic digestion.To optimize the key factors of sludge bio-char preparation,the processes of pyrolysis carbonization from sewage sludge and sludge solid matters after thermal-alkaline pretreatment were studied.Research result show that bio-char prepared from sludge solid matters after thermal-alkaline pretreatment can get the highest specific surface area with low energy consumption and the optimal factors are 600.0oC(22.5oC/min),1.0 h with N2 condition.The thermal-alkaline pretreated sludge bio-char with the optimal conditions contains large amount of functional groups(such as hydroxyl,carboxyl,carbonyl and so on)and the BET specific surface area(89.906 m~3/g),pore diameter(9.664 nm)and pore volume(0.188 cm~3/g)are higher than that of sewage sludge bio-char with the same condition(62.651 m~3/g?9.102 nm?0.141 cm~3/g respectively).The processes of cationic dyes removed from water solution by sewage sludge bio-char and thermal-alkaline pretreated sludge bio-char were studied respectively.The research result show that the adsorption process for cationic red X-GRL and cationic yellow X-6G can be well fitted by pseudo-second-order kinetics model and Langmuir isotherm model.The initial pH value is one key factor and the higher initial pH value,the higher adsorption efficiency was.The adsorption capacity of thermal-alkaline pretreated sludge bio-char was better than the adsorption capacity of sewage sludge bio-char with the same adsorption condition.The analysis results show that the cationic dye removal mechanisms may include adsorption,surface complexation and ion exchange.