Literature Review & Summary Report Design Basis Memorandum St. Johns River Water Management District Contract # SK940AA
BCI Project No. 19-15089 September 2007 Page 35
1) Dryer filter cake, therefore, greater waste volume reduction 2) Capable of effectively dewatering a wide variety of sludge streams 3) Chemical and filter aids are generally less expensive 4) Basic and durable operation
1) Batch process that typically requires more labor/operator effort 2) Lower process/production rates compared to belt press technology 3) Susceptible to cloth blinding on most oily or “tacky” sludge streams
1) Continuous feed process typically requiring less labor/operator effort 2) Higher sludge processing/production rates compared to filter press and centrifuge technologies 3) Fairly basic and durable operation 4) Best technology for bio-solids and primary/ secondary digested sludge
1) Typically requires more expensive polymer addition to pre-condition sludge 2) Belt press cake is not as “dry” as filter press cake, therefore, less waste volume reduction 3) Susceptible to cloth blinding by most oily or “tacky” sludge streams
Belt Filter Press
1) Sludge drying process diminishes volume of sludge making the transportation cost lower and storage easier. 2) Drying increases sludge calorific value; makes it hygienic, stabilizes it and improves its structure. 3) The comparison of the total costs of different sludge utilization options often indicates sludge drying as the best option.
1) Not all drying facilities are able to dry sludge only partially. 2) Moist air collected from a dryer should undergo certain processes before it is released to the atmosphere. 3) The process of sludge thermal drying is not a cheap solution mainly because of its high energy demand. 4) As thermal drying of sludge inquires significant amount of energy it is advised to use biogas, energy from sludge or waste incineration or other “waste” energy for diminishing the amounts of fossil fuels.
Table 3 Continued Dewatering Technologies Advantages and Disadvantages
Mitchell Dryers Ltd Denton Holme, Carlisle, Cumbria CA2 5DU England