Avaliação da qualidade das águas do açude Velho (Campina Grande, PB).

Abstract

During August }9S9 to September 1990, the Acude Velho (Campina Grande, PB), was evaluated, using physico-chemical and microbiological parameters. Twelve points were analized (APHA, 1985) for temperature, pH, dissolved oxigen, BOD5, transparency, turbidity, ammonia, nitrate, soluble ortophosphate, chlorophyll "a", faecal coliforms and streptococci. The results showed an homogeneus quality for central points while heterogenity characterized the margins points, due domestic sewage in drainage water entering to the dam. Mean values of BOD5 varied from 11 to 68 mg/i showing high concentrstions of biodegradable organic matter. The faecal nature of this organic pollution was confirm by the faecal coliforms and streptococci high values. The lower dissolved oxigen values werw found in sewage entrance points and the maximium in central points and where algae acumulated. Nitrate and phosphate levels did not limitated phytoplancton grwths, with predominance of blue-green algae. The low chlorophyll "a" level werw related to the presence of Microcytis. Daily cycles studies showed interferences by rain, rising turbidity and faecal bacteria values. The pollution of Acude Velho was essencially of faecae origin, due of clandestine sewage descharges. High leves of feacal coliforms comdemned this water for fishing and recreacional use. In order to stop this process sewage discharges should be eliminated, with removal of botton sludge and surface macrophytes.