Treatment of waste products with anaerobic digestion
A waste stream is treated by anaerobic digestion. A process is described involves a step of separating solids from digestate, and returning separated solids to a digester. Optionally, there may be a step of solids separation in which larger solids are removed from the digester. A process and apparatus are described for treating waste sludge from a wastewater treatment plant in an anaerobic digester. Feed sludge is thickened or solids are separated from digestate and returned to the digester. Additional co-digestion waste may be added to the digester. The process and apparatus may be used in a retrofit of an existing wastewater treatment plant.
1. A process for treating WWTP sludge comprising the steps of,
feeding the WWTP sludge at 12-20% TS to an anaerobic digester;
operating the anaerobic digester at 6-12% TS without recuperative thickening; and,
dewatering digestate in two stages.
2. The process of claim 1 further comprising adding nutrients to the digester in an amount effective to alleviate ammonia toxicity.
3. The process of claim 1 further comprising mixing the digester with a hydraulic or electric motor mixer.
4. The process of claim 1 comprising feeding the WWTP sludge at 15-20% TS to the anaerobic digester.
5. The process of claim 1 wherein the digestate is dewatered without a polymeric dewatering aid in a first stage and dewatered with a polymeric dewatering aid in a second stage.
6. The process of claim 1 wherein a portion of the WWTP sludge is dewatered before being fed to the anaerobic digester.
7. A process for treating WWTP sludge comprising the steps of, feeding the WWTP sludge at 1-5% TS to an anaerobic digester;
operating the anaerobic digester at 4-6% TS; and,
providing recuperative thickening for the digester by way of a side stream thickener; and,
adding a polymeric thickening aid in the side stream,
wherein the polymeric thickening aid is added at 3 kg/MT-TSS or less.
8. The process of claim 7 wherein waste digestate is dewatered separately from the side stream.
9. The process of claim 8 wherein a polymeric thickening aid is added at 7 kg/MT-TSS or less for dewatering.
10. The process of any claim 7 further comprising mixing the digester with a hydraulic or electric motor mixer.