Nutrient removal simulation of rendering wastewater in SBR systems

Abstract

ABSTRACT: The meat rendering process transforms waste from the meat industry to useful and valuable material as by-products (i.e. animal feed supplements), soaps and rustproofing paints. To produce animal feed supplements the hydrolysis process of lipids and proteins is fundamental to prevent the spread of diseases, during this hydrolysis process and housekeeping procedures large amounts of wastewater with high organic substances, acids, and nutrients are released to the environment imposing a huge pollution challenge, especially for biological treatment stages in developing countries with basic industrial wastewater infrastructure. Wastewater simulation is an alternative treatment forecasting of biological process, that could help to control and operate such a complex system under both dynamic and steady-state conditions. However, the influent and model parameters calibration is not an easy task, because of the lack of knowledge and standardized procedures for industrial wastewater systems. Thus, the main objective of this work is to evaluate the removal of carbon and nitrogen from an sequencing batch reactor (SBR) of housekeeping wastewater (HKWW), condensate wastewater (CWW), and the differential overload of both wastewater lines by means of simulations, following the recommendations of the activated sludge modelling (ASM) unified protocol from the good modelling practices task group, defining the two different wastewaters production, processing and analyzing the collected data, setting the plan model layout, proposing a calibration methodology for simulations of meat industry effluents based on sludge production, carbon and nitrogen performance, and analyzing how the influent fractionation, and model parameter influence the sensitivity of the treatment representations. The HKWW simulation presents that the organic matter is partially and physically removed rather than biologically since the phosphorus deficit, and pH inhibition that limits ordinary heterotrophic organisms (OHO) growth. While nitrogen presents almost no removal as a result of low pH, ammonia inhibition, and low inorganic carbon source for autotrophic nitrifying organisms (ANO). On the other hand, the CWW simulations present a higher organic matter removal for this matrix than for HKWW, since it presents a higher biodegradable content. In this case the major stripped macronutrient removal is nitrogen rather than carbon, because CWW matrix presents a higher nitrogen content and basic pH that promotes the ammonium formation and its later release to the atmosphere. Thus, for the correct biological treatment performance, the system requires adjustment in the preliminary and primary treatment for free, disperse and emulsifying oils removal to avoid fats, oil and grease (FOG) overloading and hereafter microorganism’s washout, the reduction in the aeration pattern to promote nitrifiers growth due to the increment in CO2 concentrations, and the addition of alkali species to prevent nitrifiers inhibition.