Digestion of biosolids in wastewater
A method enhancing biological digestion of wastewater sludge is provided. The method uses chlorine dioxide to accelerate and improve the efficiency of aerobic or anaerobic digestion.
1. A method of treating a wastewater product comprising:
introducing the wastewater into a biological treatment unit to provide a wastewater having a reduced nutrient content;
separating the wastewater having the reduced nutrient content to provide an effluent and a waste activated sludge;
transporting the waste activated sludge in a conduit, the conduit being fluidly connected to a source of chlorine dioxide;
contacting the waste activated sludge with the chlorine dioxide for a period of time sufficient to reduce a concentration of microorganisms in the waste activated sludge and provide a treated waste activated sludge having no residual chlorine dioxide;
dewatering the treated waste activated sludge to provide a dewatered product;
seeding the dewatered product with microorganisms to provide a seeded product; and
composting the seeded product at a temperature of less than 60° C. while maintaining an ORP greater than 0 mV to provide a Class A biosolids product.
2. The method of claim 1 , wherein the period of time for contacting the waste activated sludge with an amount of chlorine dioxide is less than 15 minutes.
3. The method of claim 2 , wherein the period of time for contacting the waste activated sludge with an amount of chlorine dioxide is less than 10 minutes.
4. The method of claim 1 , wherein contacting the waste activated sludge with an amount of chlorine dioxide comprises adding the chlorine dioxide at a dose rate in a range of about 30 to 160 mg/L of the waste activated sludge.
5. The method of claim 1 , further comprising adding at least one of wood-waste or green-waste prior to composting.
6. The method of claim 1 , wherein composting the seeded product further comprises using a forced-air aerated static pile.
7. The method of claim 1 , wherein contacting the waste activated sludge with an amount of chlorine dioxide for a period of time sufficient to reduce a concentration of microorganisms in the waste activated sludge comprises reducing a concentration of fecal coliform bacteria in the waste activated sludge.
8. The method of claim 1 , wherein introducing the wastewater into a biological treatment unit comprises introducing a municipal wastewater.
9. The method of claim 1 , wherein transporting the waste activated sludge comprising transporting the waste activated sludge at a flow rate of about 100 gpm.
10. The method of claim 1 , wherein the chlorine dioxide is generated on-site.
11. The method of claim 1 , wherein the chlorine dioxide mechanically alters the cell wall of the waste activated sludge.
12. The method of claim 1 , wherein the treated waste activated sludge meets Class B pathogen reduction requirements.
13. The method of claim 1 , further comprising drying the seeded product prior to composting.