Worksop CD Editorial

Worksop STW & STC Operator Severn Trent Water Location The plant is situated in North Nottinghamshire and receives wastewater through a mixed gravity and pumped collection system from a domestic, commercial and industrial catchment including the town of Worksop. Population equivalent 50,800 Dry weather flow 10,500 m3 /day Key processes Filtration Nitrogen removal Sludge drying and disposal Discharge Consents 25:45:5 Phosphorus The Works The plant currently comprises: Screened inlet works with grit remov4 Number Stormwater Tanks and 3 4 Number rectangular blocks of FTanks Currently under construction is a ni£1m) which will enable the works to Sampling point and final effluent diswater supply for North Nottinghamscontrol is required of discharges ssources. The area has a recent histled to high levels of backgroun Bio-solids treatment and disposalA new sludge dryer (value £2m) isstage centrifuge/dryer will convert 2,85% t.d.s. for final disposal to agricUK. Worksop STW: sludge dryer (underconstruction - July 2003) al and screenings washing Primary Sedimentation Tanks ilter Beds and 3 Number Final Settlement trifying submerged aerated filter plant (value achieve the revised phosphorus consents. charge to the river Rayton. Much of the raw hire is from groundwater boreholes and strict o as not to contaminate these raw water ory of coal extraction and cleaning which has d contamination of local water courses. currently being commissioned. The single 400 tonnes of bio-solids p.a. to pellet form at ulture. This plant is the first of its type in the 12345678910111213abcdefghik12345678910111213abcdefghik1 CENTRIDRY ®2 Polymer preparation3 Hot - gas generator 4 Cyclone/Product separator5 Chain conveyor6 Screw conveyor/Mixer7 Circulating fan8 Exhaust fan9 Venturi scrubber10 Condenser 11 Pelletiser 12 Pellet Cooler 13 Bagging unit Centridry Process parameters INPUT a Sludge b Polymer ? Evaporation rate 1.7 t/h H2O c Potable water? Liquid sludge input 5 – 5.5 % d.s. d Fuel ? Liquid throughput approx. 18m3/h e Combustion airf Effluent water? Output before pelletising 80 % d.s g Air ? Pellet size 6mm diameter ? Thermal power 5.7Mj/h OUTPUT ? Electrical power 350 kW/h h Centrate ? Fuel source – LPG Propane / natural gas i Waste waterk Exhaust l Pelletised product Process description Liquid sludge combined with polymer is pumped into a modified centrifuge where conventional mechanical dewatering takes place. The dewatered sludge at the dewatering stage needs to reach a minimum d.s. of 25% and is discharged into the thermal stage as a fine-grained spray. The CENTRIDRY® has an additional insulated outer casing compared to a standard Centrifuge. Hot vapour is drawn at high speed through the circuit from the hot gas generator. The sludge particles are discharged from the mechanical dewatering stage into the outer cyclone chamber of the Centridry where they are instantly dried. The particles are entrained and conveyed in the sweep gas and exit the jacket in a matter of seconds during which time the sludge granules are dried and the temperature of the conveying vapour is dramatically reduced. The pneumatic conveying and drying process continues during the relatively short transport time to the cyclone where the product particles are separated from the vapour and discharged via a rotary valve to the elevating chain conveyor. The product is further conveyed via a paddle mixer to a pelletising machine where 6 mm pellets are produced followed by a cooling stage. On discharge from the cooler the pellets can be discharged to either a bagging station or to a bulk loading station. Discharge port of Centrifuge stage Pelletiser and cooler The sweep gas, is drawn through the system by via the main ventilator fan and is re-heated in the hot gas generator before re-entering the dryer loop. Excess vapours in the system are drawn off the system by a small blower, and following treatment in a venturi scrubber to remove residual quantities of fine dust and volatile components, are discharged to atmosphere. The process is controlled by an MCC with ICA section comprising a Mitsubishi PLC with additional Industrial PC to provide HMI displays and process trending reports. MCC & ICA