| With the development of cities and improvement of people' living standard,more and more sludge are produced.Sludge drying is one of the important processing methods of excess sludge reduction.Bio-drying is a new technology with a broad application prospect which could avoid the existing problems of drying technology such as high energy consumption and time consuming.But there are many problems of Bio-drying to be solved.Sludge of North Shenyang Sewage treatment plant is used to study different air-flow rates' effect on Bio-drying.And oxygen consumption of different stages is studied under the optimal air-flow rate.Experimental period is unified set to 6 days.Three stages of temperature are found which are warming of mesophilic bacteria,warming of thermophiles and cooling of bacteria decline growth.Two stages of water removing are found which are the low temperature drying stage with mesophilic bacteria and the high temperature drying stage with thermophiles.Drying efficiency of air-flow rate 2.8m3/h is highest.And the temperature of it rise from 48.5 ? to 68.7? in the time period of 56h-104h which has the biggest change of temperature gradient.The temperature stays at about 68.6? for 32h and falls after 108h.The highest temperature appears on 76h which is 68.8?.Water content significantly decreases after 72h and it falls by 45.6%in the whole cycle.Sludge oxygen consumption rates of each stage are measured under the air-flow rate of 2.8m3/h which are 0.504m3/h,0.56 m3/h,0.7 m3/h,0.812 m3/h,0.728 m3/h and 0.616 m3/h from day 1 to day 6.The Sludge oxygen consumption rates of day 3 is the largest one of them.Heat production rates of sludge are got which are 0.714KJ/m3·h,0.793 KJ/m3·h,0.991 KJ/m3·h,1.150 KJ/m3·h,1.031 KJ/m3·h and 0.872 KJ/m3·h.The result of this study would provide a scientific basis for bio-drying's optimization and promotion and it could also provide a basis for the sludge's further disposal of city sewage plants in Shenyang area. |
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