Anaerobic hydrolysis of a municipal wastewater in a pilot-scale digester
Alvarez, J.A.; Zapico, C.A.; Gómez, M.; Presas, J.; Soto, M.
Water Science and Technology a Journal of the International Association on Water Pollution Research 47(12): 223-230
2003
ISSN/ISBN: 0273-1223 PMID: 12926692 Document Number: 553471
Raw domestic waste water from the city of Santiago de Compostela (Northwest Spain) was fed into a pilot-scale hydrolytic up flow sludge bed digester with an active volume of 25.5 m3. The total influent chemical oxygen demand (COD) ranged from 360 to 470 mg/litre, the influent suspended solids (SS) varied from 190 to 370 mg/litre, and the temperature was between 17 and 20 degrees C. The organic load rate applied increased step by step from 1.2 to 3.9 kgCOD/m3.day, while the hydraulic retention time (HRT) decreased from 7.1 to 2.9 h. A high SS removal of approximately 82-85% from the influent was reached, most of which (81 to 88%) was eliminated by hydrolysis, while the rest remained in the purge stream. The total COD removal ranged from 46 to 59%. On the other hand, a high acidification of the COD remaining in the effluent was obtained, so the percent COD in the form of volatile fatty acids (VFACOD) with respect to total effluent COD was approximately 43% for the highest HRT applied, and approximately 27% for the lowest HRT. The soluble to total COD ratio (CODs/CODt) increased from 25-32% for the influent to 71-86% for the effluent. The results obtained confirm the viability and interest of direct anaerobic hydrolytic pre-treatment of domestic waste water.