Bacteriological - related probability of underground water on the coastal zone of Aquiraz county, Brazil

Abstract

The data dealt with in this paper are related to bacteriological analyses of the underground water found along the coastal zone of Aquiraz County, Ceará State, Brazil. The geological conditions are represented by sedimentary lithotypes which comprise the Barreiras Formation, eolian deposits of dunes and paleodunes, alluvial patches and mangroves, whencefrom aquiferous, homonymous systems are characterized. The results show that 63.6% of the 11 analyzed samples are contaminated with fecal bacteria, among which Escherichia coli predominates with 55.4% as an indicator of the fecal coliform group. The presence of nitrate was spotted in 99% of the samples, with 36.3% of them showing higher values than the allowed maximum, namely 10 mg/L of N-NO3 -, varying from 15.4 to 29.9 mg/L of N-NO3, a condition that renders the water non drinkable and potentially determinant of hemoglobinemy. Those features reveal a vulnerability of the aquiferous systems to bacteriological and chemical contaminations, specially in zones where the sewage disposal system is made out of a network of patent concrete cesspits. The absence of technical criteria for the construction and location of water wells, and the widespread practice of patent concrete cesspit usage in place of major sewage disposal works, make up the basic factors which are likely to bring about bacteriological contamination.