Fecal bacteria contamination in Lake Huayamilpas, Mexico, D.F.

Abstract

The water sanitary quality was evaluated following a restoration program for native fish species introduction in an urban lake, Huayamilpas. The Most Probable Number of total coliforms (T.C.), fecal coliforms (F.C.) and streptococci (F.S.) were determinate as indicator organisms in water and sediment every month (1997-1998) at the main pond and  the inflows. The T.C. bacteria were above the limits for recreation water (in 83% of the samples), the F.S. group was above the norm for aquatic life organisms protection (in the 67% in the inflows), the F.S. bacteroa were 55% over those limits on the samples from the pond. The bacteria concentrations in sediments were 100 times grater than in the column of the pond, and 300 higher than the inflows. These sections could be identified: the main pond with low percentage of contaminated samples (T.C. 5%, F.C. 11%, F.S. 28%); the secondary pond with intermediate levels (T.C. and F.C. 20%, F.S. 60%); and the inflows (T.C. 77%, F.C. 61%, F.S. 85%) with the highest levels. The poor bacteriological quality of the inflows was attributed to the sporadic drainage of domestic wastewater. The F.S. contamination was associated to the presence of the birds. F.S. is a relevant indicator to considerate for the fish introduction of native species. Water quality can be improved by avoiding the contamination by the water inflows prior to its entry to the lake, and by the recommendation of controlling bird population.