OPTIMAL-DESIGN FOR ANAEROBIC PRETREATMENT OF MUNICIPAL WASTE-WATER

In recent years the advent of the anaerobic expanded bed reactor (AEBR ) has made possible the treatment of wastewaters of comparatively lowe r strength than have been treated traditionally by anaerobic means. Ho wever, regardless of any benefits presented by its use, the process mu st be shown to be cost effective relative to other options before it w ill gain acceptance. This paper reports on the results of a series of optimization exercises in which the costs of the AEBR as an expansion alternative for organically overloaded treatment plants are compared w ith costs for more conventional remedies. The optimization model devel oped includes the unit processes of primary clarification, AEBR, trick ling filtration, secondary clarification, activated sludge, gravity th ickening, anaerobic digestion, and vacuum filtration. Several constrai nt parameters were varied to determine the cases for which the AEBR wo uld be the cost-effective option. These parameters were primary efflue nt chemical oxygen demand (COD), hydraulic loading, temperature, cost of labor, cost of power, cost of sludge disposal, and amortization int erest rate. The results suggest that the AEBR may be a competitive sol ution for organically overloaded facilities under selected conditions.