BIOLOGICAL OXIDATION OF Y9 INDUSTRIAL HAZARDOUS WASTEWATER: INOCULUM EFFECT

NIEVAS EL MAKTE M.L.; POLIFRONI R.; DEL BRIO F.; DEL PRADO G.

BUENOS aiRES - VIRTUAL

Congreso; XVI Annual Meeting of the Argentinean Society for General Microbiology (SAMIGE); 2021

SAIB / SAMIGE

Industrial wastewaters possess a variety of characteristics depending onthe production processes where they are generated. Many metal-mechanicsindustries and industrial machine and vehicle washing facilities generate oilywastewaters, classified by the hazardous waste environmental normative as Y9stream ?Waste oils/water, hydrocarbons/water mixtures and/or emulsion?. Thistype of wastewater may be reclaimed utilizing biological treatment.  This work aimed to evaluate the biologicaloxidation time course of an industrial Y9 wastewater using its native microbialcommunity in comparison with a bioaugmented process. A real industrialwastewater was used to perform a laboratory assay, which was sampled after agravity separation unit. The main wastewater components were biodegradablecleaning products, hydrocarbon residues, and suspended solids in an aqueousstream. An aerobic batch reaction was carried out using a 4 L reactor with 3.3L of wastewater, with porous diffuser aeration at a 0.5 vvm rate. Two treatmentswere evaluated: raw wastewater as it was sampled and bioaugmented wastewater byinoculation with a microbial consortium obtained from the surrounding soil ofthe effluent discharge, previously grown in mineral oil as the sole carbonsource. The treatments were incubated for 81 hours at 22°C and periodic sampleswere taken to evaluate chemical oxygen demand (COD), turbidity, opticaldensity, and microbial growth. Both treatments showed a reduction in COD of73-76% in 34 hours, achieving values ​​lower than 200 mg/L along with theoxidation reactions. Turbidity increased doubling its initial value in thefirst hours, probably due to the dispersion and suspension of particles andhydrocarbon droplets contained in the wastewater. Subsequently, the turbidityshowed a decrease according to the COD values. The optical density reflectedboth the microbial growth and the decrease in the COD effect. In bothreactions, heterotrophic counts reach up to 6-7 107 CFU/ml in 48 h,maintaining this concentration order along the studied period. The rawwastewater did not show an inhibitory effect, making it evident that the nativewastewater microbial community was able to biodegrade the organic matterpresent, in a similar way to the inoculated one. Based on these results, it canbe estimated that for a system of biofilm reactors, which are generally moreefficient than batch systems, a retention time less than that established inthis experiment would have similar biodegradation results. Thus, a hydraulicretention time of 28 hours may be adopted as a conservative criterion using a 0.5L/min flowrate in a continuous bioreactor pilot scale as starting operationpoint without external inoculum addition.