Win-win solution for biogas plant
Published: 11 January 2012 - Heather Ramsden
Problem: Cog Moors waste water treatment plant in South Wales was experiencing reduced gas yield from its on-site digestion of sewage sludge due to the fact that the digester recirculation tanks were producing small amounts of gas causing the impeller pumps to lock and stop flow. Downtime, reduced heat retention in the digester were also happening while ragging was causing more downtime issues with existing pumps.
Solution: Welsh Water asked seepex to assist. Within two days seepex had shipped a loan pump to Cog Moors to provide an immediate solution to the problem. They assisted in the commissioning of the seepex progressive cavity pump which is a self priming positive displacement pump capable of handling entrained gas. The loan pump enabled the plant to continue effective gas production. Meanwhile a larger seepex pump was designed to provide the exact flow rate and eliminate ragging.
The new seepex pump was designed with smart stator to allow easy in situ maintenance without dismantling the pipework. A combination of the pumps capability to handle entrained gas, together with the unique features of smart stator and the fitting of an anti-ragging device has improved gas yield by providing a constant flow of sludge, which has in turn resulted in the correct temperature of sludge feeding the digester.
The inclusion of smart stator proved a real hit. It is so popular with the site engineers that Welsh Water has now specified that all existing and new seepex progressive cavity pumps on site be upgraded to this latest seepex technology.