Controlling biosolids phosphorus content in enhanced biological phosphorus removal reactors.
A methodology to reduce the phosphorus content of biosolids produced by enhanced biological phosphorus removal treatment plants was studied. The process consists of mixing phosphate-rich waste activated sludge (WAS) with either primary sludge or the supernatant from a primary-sludge gravity thickener under anaerobic conditions to induce the release of phosphate from WAS. The solubilized phosphate could then be chemically sequestered and removed from the biosolids. Bench-scale phosphate release experiments were conducted with sludge from the Nine Springs Wastewater Treatment Plant (Madison, Wisconsin) at different mixing ratios. A WAS/primary sludge or WAS/supernatant mixing ratio of 1:1 (by volume) resulted in the highest phosphate release in the batch tests. For experiments with less than 50% WAS (by volume), the total phosphate release was directly proportional to the amount of WAS added. When the mixture contained more than 50% WAS, total phosphate release was limited by the volatile fatty acids (VFAs) available. For the Nine Springs plant optimal biosolids phosphorus could be achieved using a primary sludge/WAS mixing ratio of 1.02 kg volatile suspended solids (VSS)/kg VSS or a supernatant VFA/WAS mixing ratio of 0.028 kg VFA/kg VSS. The expected reduction in phosphorus content would be 35 and 32% if primary sludge or supernatant, respectively, were used.
Chaparro
Sean K
SK
Malcolm Pirnie, Inc., Detroit, Michigan, USA.
Noguera
Daniel R
DR
D001421:Bacteria, Anaerobic / Q000502:physiology; D019149:Bioreactors; D010758:Phosphorus / Q000302:isolation & purification*; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014873:Water Pollutants / Q000302:isolation & purification*
D012722:Sewage; D014873:Water Pollutants; D010758:Phosphorus