PERFORMANCE OF 2 MUNICIPAL SEWAGE STABILIZATION POND SYSTEMS WITH HIGH AND LOW LOADING IN SOUTH-EASTERN SPAIN

From January to December 1992, the efficiency of two waste stabilizati on pond systems (WSPS) located in the Region of Murcia South-eastern S pain, has been studied in terms of the physicochemistry and the microb iology of the systems. The efficiencies of the different stages of the treatment and the global performance have been compared. The WSPS of Lorqui and Ceuti (12,000 inhabitants) receives fruit processing aid ca nnery wastes mixed with the urban sewage. This increases the load up t o 95,000 equivalent inhabitants with an average BOD5 of 800 mgO(2)/I. Global reductions of COD and BOD5 were 79% and 73% as a yearly average . The mean of the reductions of indicator microorganisms were: colipha ges (CHP), 83.14%; total coliforms (TC), 72.90%; faecal coliforms (FC) , 93.84% and salmonellae (SAL), 98.29%. The WSPS of San Javier (15,000 inhabitants), situated at the border of the Mediterranean, does not r eceive industrial wastes but suffers from intrusions of marine waters into the sewers. BOD5 is diluted by the intrusion to less than 100 mgO (2)/l, even in summertime when population doubles because of the touri sm. Average yearly reductions of COD and BOD5 were 32% and 21%. The me ans of the microbiological reductions were: CHP, 81.60%; TC, 90.77%; F C, 94.37% and SAL, 99.42%. Design constants have been calculated for b oth systems considering the climatic conditions of the area.