A hydrobiological survey of a small Spanish river grossly polluted by oil refinery and petrochemical wastes

Abstract

SummaryIn a 2½‐month hydrobiological survey of the Rio Ojailén, a tributary of the Rio Guadalquivir in Spain, four aspects of the pollution from an oil refinery and petrochemical complex were considered: physical, chemical, macrobiological and toxico‐Iogical. Near its source the river receives a combined waste making up 75% of its dry weather flow. The wastes are grossly polluting‐from oil, phenols, ammonia, hydrocarbons and other organic materials as well as suspended solids. Though inhibitory to biological degradation, the wastes are gradually purified and diluted with passage downstream and retention in a man‐made lake. No macroinvertebrate life is found for 43 km downstream of the complex, in spite of incoming pure streams which were sampled for comparison. Diptera followed by Odonata are the first to return. The effect of the lake on purification is considerable. Toxicity tests of river water upon mosquito fish show a similar decline in toxicity. An attempt has been made to predict the recovery of the river once treatment plants have been installed by the autumn of 1973.