Optimizing dewatering of biosolids from autothermal thermophilic aerobic digesters (ATAD) using inorganic conditioners

Biosolids obtained through the autothermal thermophilic aerobic digestion ( ATAD) process exhibit greater polymer demand for dewatering than those obta ined through conventional mesophilic aerobic digestion processes. An increa se in ATAD retention time and operating temperature resulted in an increase in proteins and polysaccharides in solution, and this resulted in a corres ponding increase in cationic polymer demand and an increase in dewatered ca ke filtrate chemical oxygen demand (COD). Alternative chemical conditioners were used to minimize polymer consumption. Coagulation of solution phase b iological polymers (proteins and polysaccharides) using ferric chloride or alum was extremely effective in reducing cationic polymer conditioning dema nd and dewatered cake filtrate COD. Ferric chloride and alum in laboratory experiments were also able to precipitate and remove phosphate, thus preven ting its recycle to the influent of the plant.