NPE were engaged by Newcastle City Council to provide an efficient, cost-effective and environmentally sustainable solution to desilt a lined leachate pond and subsequently dewater the sludge to produce dewatered cake with at least 20% dry solids content at the Summerhill Waste Management Centre. Desludging and dewatering works were initiated by the council to restore the holding capacity of the pond, allow inspection of the liner integrity, and assess adopted technology performance.

NPE proffered a turnkey sludge dewatering solution that utilised a containerised screw press that reduced sludge volume by at least 80% in a single step. The leachate sludge dewatering system included the installation of a sludge screw press, sludge thickening tank, macerator pumps, slurry pumps, water cannon, sludge bin, potable water tank, chemical/polymer tanks and dewatering fittings and accessories. Bunding of the screw press area was also undertaken to contain leachate leaks.

The enclosed design ensured a reduction in odour and noise during operation. The relatively low energy demand of the screw press, owing to its low operating speeds, compared with other sludge dewatering techniques, was an added benefit. Once polymer dosing was optimised to yield desirable robust flocs, the containerised screw press provided an efficient, fully automatic mechanical sludge dewatering.

The screw press produced an average of 178 kgs of dry solids/hour with at least 90% solids capture rate. Daily screw press operations were optimised for a 4-5 wt% total solids feed sludge and max feed sludge flow rate of 4 500L/h with an average active polymer usage of 4.4-6.8kg/ dry tonne with a mean cake dryness of 42% achieved. A maximum of 47% and a minimum of 38 % cake dryness were achieved during operations.

The project demonstrated NPE’s capability to provide an integrated sludge management solution, assisting clients in significantly reducing their sludge disposal costs.