Polymer split-dosing trial for optimising the dewatering of thermally hydrolysed digested sludge at Long Reach Sewage Treatment Works: PRESENTATION ONLY
Tilahun, D., Rus, E., Fountain, P., Christie, I., Thames Water Utilities Limited, UK
(free)
The full scale dewatering of thermally hydrolysed digested sludge at Long Reach Sewage Treatment Works (STW) was found to be underperforming both in terms of polymer demand and cake dry solids content when compared to other sites and laboratory scale dewatering results. This study examines the causes behind these differences and options for improvements.
Several laboratory scale trials were undertaken in order to examine the dewaterability of digested sludge using two different types of polymer application methods; single-dosing and split-dosing. Results obtained from these investigations indicate that by split-dosing; the sludge flocculated better, the filtrate release increased by 7.3%, dewatered significantly better and the cake dry solids content increased by 2.8%. Most significantly, by split-dosing the polymer demand was reduced by 13kg/tds.
Following these laboratory results, full-scale trials were conducted at Long Reach STW using two Bucher presses in parallel; one with a single-dosing polymer application and one with split-dosing polymer application.
Results obtained from this full scale trial confirmed the previous laboratory results. The split-dosing reduced the polymer demand by 7kg/tds, increased the cake dry solids content by 3.8% and increased throughput by 2,553 litres per batch compared to the normal application of Single-dosing being used at the site.
The findings demonstrate the potential for significant annual cost savings of £210,438 in terms of polymer consumption and sludge cake transportation.
Key words: Thermal Hydrolysis; Polymer; Single-Dosing; Split-Dosing; Bucher Press; Sludge; Cake Dry Solids; Throughput.
