BIOLOGICAL OXIDATION OF Y9 INDUSTRIAL HAZARDOUS WASTEWATER: INOCULUM EFFECT

MARINA NIEVAS EL MAKTE; ROSANA POLIFRONI; FEDERICO DEL BRIO; LUJÁN PANGRAZZI

Buenos Aires

Congreso; LVII SAIB Meeting - XVI SAMIGE Meeting; 2021

SAIB - SAMIGE

BIOLOGICAL OXIDATION OF Y9 INDUSTRIAL HAZARDOUS WASTEWATER: INOCULUM EFFECTNievas El Makte ML1,2, Polifroni R1, del Brio F, Pangrazzi L3.1Centro para el Estudio de Sistemas Marinos (CESIMAR-CONICET), Puerto Madryn. 2Universidad Tecnológica Nacional, Facultad Regional Chubut, Puerto Madryn. 3 E.I.S.I. S.A., Puerto Madryn.E-mail: nievas@cenpat-conicet.gob.ar marina_nievas1@yahoo.com.arIndustrial wastewaters possess a variety of characteristics depending on the production processes where they are generated. Many metal-mechanics industries and industrial machine and vehicle washing facilities generate oily wastewaters, classified by the hazardous waste environmental normative as Y9 stream “Waste oils/water, hydrocarbons/water mixtures and/or emulsion”. This type of wastewater may be reclaimed utilizing biological treatment. This work aimed to evaluate the biological oxidation time course of an industrial Y9 wastewater using its native microbial community in comparison with a bioaugmented process. A real industrial wastewater was used to perform a laboratory assay, which was sampled after a gravity separation unit. The main wastewater components were biodegradable cleaning products, hydrocarbon residues, and suspended solids in an aqueous stream. An aerobic batch reaction was carried out using a 4 L reactor with 3.3 L of wastewater, with porous diffuser aeration at a 0.5 vvm rate. Two treatments were evaluated: raw wastewater as it was sampled and bioaugmented wastewater by inoculation with a microbial consortium obtained from the surrounding soil of the effluent discharge, previously grown in mineral oil as the sole carbon source. The treatments were incubated for 81 hours at 22°C and periodic samples were taken to evaluate chemical oxygen demand (COD), turbidity, optical density, and microbial growth. Both treatments showed a reduction in COD of 73-76% in 34 hours, achieving values lower than 200 mg/L along with the oxidation reactions. Turbidity increased doubling its initial value in the first hours, probably due to the dispersion and suspension of particles and hydrocarbon droplets contained in the wastewater. Subsequently, the turbidity showed a decrease according to the COD values. The optical density reflected both the microbial growth and the decrease in the COD effect. In both reactions, heterotrophic counts reach up to 6-7 107 CFU/ml in 48 h, maintaining this concentration order along the studied period. The raw wastewater did not show an inhibitory effect, making it evident that the native wastewater microbial community was able to biodegrade the organic matter present, in a similar way to the inoculated one. Based on these results, it can be estimated that for a system of biofilm reactors, which are generally more efficient than batch systems, a retention time less than that established in this experiment would have similar biodegradation results. Thus, a hydraulic retention time of 28 hours may be adopted as a conservative criterion using a 0.5 L/min flowrate in a continuous bioreactor pilot scale as starting operation point without external inoculum addition.