INNOVATION May-June 2014

MicroSludge unit at Catalyst Paper’s Crofton, BC, plant.

and it releases the cytoplasm (the cell’s liquid contents) for consumption in the wastewater treatment plant’s anaerobic digester. The system works in such a way that sewage enters a primary settling tank and heavier primary sludge material settles out and flows to an anaerobic digester. The watery material that is left goes to an aerobic treatment system where the introduction of air promotes bacterial growth. The aerobically treated wastewater then goes to a second clarifying tank where clarified water that is safe for discharge is released. Settled sludge from this second tank is directed toward the anaerobic digester. But, before the sludge reaches

this digester, it passes through the MicroSludge process, in order to disrupt the cells’ walls. MicroSludge-processed sludge flows to the anaerobic digester, joining the primary settlement sludge where it produces biogas. Anaerobic digester effluent is then dewatered—a process whereby water is separated from the digested sludge—and the water then goes back to the primary settling tank, while the dewatered sludge goes to disposal. Neill points out that anaerobic digesters have previously only been used to reduce the amount of waste-activated sludge (WAS) slightly. “Typically by about 25 – 30%,” he says. The MicroSludge tech- nology of bursting cells is like someone popping a water balloon. “By liquefying WAS, we are increas- ing the solids destruction to about 50% in the digester,” he says. To complement the MicroSludge process, Paradigm has designed the Closing the Loop system, which cycles the WAS from the secondary clarifier back through MicroSludge to the anaerobic digester. It is then returned back (without sludge dewatering) to the aerobic treatment system. The combination of cell lysis and anaerobic and aerobic digestion in the activated sludge system has resulted in up to an 80% decrease in WAS at demonstration scale. “We are using MicroSludge and the aerobic wastewater treatment plant to help destroy its own sludge by-products,” says Neill. “And the results are very exciting.”

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