Microorganism removal in wastewater stabilisation ponds in maracaibo, Venezuela

Abstract

Waste stabilisation ponds are an efficient means of wastewater treatment in many parts of the world wherever suitable land is available at reasonable cost and solar energy is an abundant energy resource. This study evaluated the removal of total coliforms TC, faecal coliforms FC and coliphages C in waste stabilisation ponds functioning as a pilot system in the tropical climate of Maracaibo, Venezuela. Sampling points included raw sewage and each pond effluent. Turbidity, pH and temperature were recorded. The results for raw sewage show average levels of 4.1×106 TC, 2.8×106 FC and 7.0×105 C/100mL. Temperature, pH and turbidity ranges between 26–31°C, 6.2–9.5 and 15–98 NTU respectively. Removal of microorganisms in the three systems ranged between 93–98%. Despite the high removal efficiency of microorganisms, the final effluents showed average counts of 5.4×104−1.4×105 TC, 5.2×104−1.3×105 FC and 1.6×104−4.7×104 C/100mL. This study shows that the microbiological quality of the final effluents did not achieve the WHO water quality requirement for FC (103/100mL); therefore, they cannot be used for irrigation. Additional treatments, such as slow sand filtration, are needed in order to improve the quality of the water.

Activated sludge and other suspended culture processes

“…Fecal coliform removal was found to be a function of retention time in wastewater stabilization ponds (Rangeby et al, 1997). Effluent from a pilot waste-stabilization pond in Venezuela did not achieve the World Health Organization fecal coliform requirements of 10 3 /100 mL (Botero et at., 1997). An epidemiological review of water-related Campytobacter transmission was conducted by Koenraad et al (1997).…”

Desinfección con cloro y luz UV en un proceso convencional de regeneración de agua

“…No obstante, la reutilización de agua residual puede comportar un riesgo sanitario para las personas, ya que la exposición a los microorganismos patóge-nos en estos casos es mayor que cuando se utilizan aguas no contaminadas con agua residual (Mujeriego, 1990;Botero et al, 1997). Las dosis adecuadas de reactivos y el método de desinfección adoptados para la regeneración de un agua residual dependen fundamentalmente de su calidad.…”