The Study Of Treatment Technology And Application On Sewage Sludge By The Subcritical-hydrothermal Method

Recently, large numbers of dewatered sludge(80% moisture content) are produced during the disposal of wastewater. Sludge quantity reaches nearly14 million tons each year,and it is expected to increase to 35.6 million tons in 2015, deep dewatering has become a key and difficult issue of sludge treatment.Hydrothermal method is an effective sludge pretreatment method to improve the performance of sludge dewatering by cracking the sludge colloid. Water hot products can realize the sludge reduction ,reuse and harmless at last(residue to absorbent, hydrolyzed water treatment by ASBR processing and absorption).This paper use continuous hydrothermal equipment to study the parameters research (temperature, pressure, pH) of sludge pyrohydrolysis dehydration effect.Result show that SCOD which is a characterization parameter of sludge dehydration effect increase with the temperature and the pressure. In the condition of reaction temperature 250℃, pH 7, reaction time 8 min, SCOD reach 8650 mg/L, the residue calorific value is 13806 KJ/Kg. SCOD reach 28225 mg/L, filtering speed increase by 37.5%-66.7% than neutral, and the residue of calorific value is 9486 KJ/Kg at pH 4.0. Comparing GC-MS of neutral with acid water after hydrotheaml treatment, it find that types of small molecules volatile organic compounds decrease, and macromolecular organic matters begin to dissolve and hydrolyze at pH 4. So the best conditions for hydrothermal sludge treatment is 250℃,pH 4,7 MPa, 8 min of reaction time.Through the orthogonal and single factor experiment, the optimum processing conditions for ACh(sludge hydrothermal residue activated carbon) is 40% ZnCl2 of concentration, 450℃of activation temperature, 30 min activation time, 1:2 of solid-liquid ratio, while the optimum process conditions of adsorbent AC0(sludge activated carbon) is 40% ZnCl2 of concentration, 550℃of activation temperature, 60 min activation time, 1:2 of solid-liquid ratio.Combined with adsorption performance characterization, process conditions for ACh made from hydrothermal residue is more optimized and cost-effective. ACh has a better adsorption performance,hydrothermal residue is also treated.Effluent of hydrothermal water treatment can meet the secondary sewerage standard by ASBR-adsorption processing.Continuous hydrothermal sludge treatment equipment with a productivity of 20t (moisture content 80% of sludge) / days is planning and preparation.Investment cost will reach 1.99 million yuan(27.6 RMB/t moisture content 80% of sludge), and the operation cost will be 153 yuan/t (moisture content 80% of sludge) when running.