Removal of enteric bacteria from a fruit juice processing wastewater treatment system

TARIFA, MARÍA CLARA; BRUGNONI, LORENA INÉS

San Miguel de Tucumán

Congreso; VII Congreso Argentino de Microbiología General "SAMIGE del Bicentenario"; 2011

Sociedad Argentina de Microbiología General

Argentina is the dominant apple juice producing country in the south hemisphere, and exports large amounts of concentrated apple juice. The ?Alto Valle de Río Negro y Neuquén? area of Argentina, located across two states in the southwest of the country, is a region where numerous processing industries are located. These industries release its effluents, previous treatment, to Río Negro River. This treatment plant has a system of three lagoons: two aeration lagoons (6,250 m2, with an incoming waste of about 15,000 m3) and one facultative lagoon (18,750 m2, with an incoming waste of about 55,000 m3) arranged in series which received different amounts of discharge according to the season. The total retention time in the plant is 14 days. One of the main objectives of the use of wastewater treatment lagoons is pathogen removal. This, in turn, determines compliance with the pertinent legislation and establishes the allowable uses of the effluent and receiving water body, such as irrigation, bathing, aquaculture, water supply and others. Prediction of bacterial effluent quality is essential to provide an indication of health risks posed by enteric contamination and to determine whether the reused lagoon water will reliably meet current health regulations. The purpose of this work was to evaluate the removal of enteric bacteria in a fruit juice processing wastewater treatment. With this purpose, samples were periodically collected in different seasons (peak season: January to July, off-peak season: August to December). In the aerobic lagoons the samples were taken from superficial zone and the facultative lagoon was divided in a superficial zone (0.30 m below the surface) and a middle zone (1.20 m below the surface). At each zone, the samples were taken at inflow and outflow of the lagoon, and then stored at 4°C until processed in the laboratory. The samples were diluted and the dilutions were plated in triplicate onto selective medium, VRBG (Violet Red Bile Agar with Glucose). The selective media plates were incubated at 35°C for 24 hours. Typical colonies were count and the result was expressed as Colony Forming Units (CFU)/mL. Along the treatment plant a reduction in enteric bacterial isolates was observed (percentage of removal between 90-99%), demonstrating the efficiency of the wastewater treatment process regardless of the season. We must keep in mind that this water will suffer a chemical treatment (chlorination) before reusing, and that it will also contribute to the reduction of enteric bacteria numbers.