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Anoxic low-lime and fly ash post-disinfection of anaerobically digested sludge to class A levels

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Abstract:

The feasibility of full-scale anoxic disinfection of dewatered and digested biosolids from Winnipeg, Manitoba with low lime doses and lagoon fly ash was investigated to determine if a class A product could be produced. Lime doses of 50g, 100g, and 200g per kg of biosolids (dry) were used along with fly ash doses of 500g, 1000g, and 1500g per kg of biosolids (dry). The mixed product was buried in eight-10 cubic metre trenches at the West End Water Pollution Control Centre in Winnipeg. The trenches were backfilled with dirt and tarped to simulate anoxic conditions. Sampling cages were packed with the mixed product and pathogens non-indigenous to Winnipeg's biosolids. The cages were buried amongst the mixed biosolids in the trench. The non-indigenous pathogens spiked in the laboratory were the helminth Ascaris suum and the enteric virus reovirus.

Samples were removed at days 12, 40, and 69. The samples were tested for the presence of fecal coliform, Clostridium perfringens spores, Ascaris suum eggs, and reovirus. The pH, total solids, and free ammonia content of the mixed product were also determined for each sample.

Fecal coliform bacteria and reovirus were completely inactivated for doses as low as 100g lime per kg biosolids (dry) and 50g lime + 500g fly ash per kg biosolids (dry). Spores of the bacteria C. perfringens experienced a 4-log reduction when treated with 100g lime per kg biosolids and a 5-log reduction when treated with doses as low as 50g lime + 500g fly ash per kg biosolids (dry) after 69 days. Ascaris eggs were completely inactivated in 5 gram packets for all treatments involving 100g lime per kg biosolids (dry) after 69 days. Class A pathogen requirements were met for all treatments involving a lime dose of at least 100g per kg biosolids.

Document Type: Research Article

DOI: https://doi.org/10.2175/193864702784162570

Publication date: 2002-01-01

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