Food processing wastewater as feedstock for microalgae growth and nutrient removal

Abstract

Meat industry generates large volumes of meat processing wastewater (MPWW), highly loaded in terms of nutrients, carbon and suspended solids. The discharge of untreated wastewater decreases water surface quality, potentially leading to death of aquatic life and eutrophication. There is a growing interest in the use of microalgae to treat MPWW, due to their ability to treat MPWW and to the potential of microalgal biomass as a biobased product, integrating the treatment process into the circular economy concept.In this study, the capability of a microalgae consortium to treat and grow in raw MPWW was evaluated. The characterization of wastewater from different production cycles revealed its wide variability in carbon and nutrient composition. The feasibility in treating raw wastewater without any pre-treatment step as well as the influence of MPWW native microbial community and suspended solids in nutrient removal and biomass growth was evaluated. MPWW was collected from a meat processing factory consisting of a mixture of cooking drums wastewater plus water used for cooling processes (1:1). Batch cultivation of a microalgae consortium in raw MPWW was conducted under different conditions. Nutrient and carbon removal and biomass growth were monitored during cultivation. In batch cultures where raw and sterile wastewater was used, the chemical oxygen demand (COD) removal rate of the native MPWW microbial community was of 125.9 mg L-1 day-1 at the first eight days, but, in the presence of the microalgae consortium, the COD removal rate increased to 138.3 mg L-1 day-1. As MPWW was used without any pre-treatment, total nitrogen and ammonium nitrogen increased probably due to dissolution of suspended solids that occurred in all the tested conditions. When using raw MPWW, the microalgal biomass growth was higher than that obtained with sterile wastewater probably due to synergistic effect established between the microalgae and the native microbial community. Carbon removal and microalgae growth were not negatively affected by the presence of solids, supporting the hypothesis that this type of wastewater can be applied as feedstock for microalgae biomass production without the need of prior treatment, thus being potentially more economically viable.The molecular analysis of the culturable microalgae isolates within the consortia used in the batch assays revealed that isolates belonged to two different genera of the Trebouxiophyceae class, namely Micractinium and Chlorella.

Date of Award	11 Feb 2021
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Catarina Leite Amorim (Supervisor), Paula M. L. Castro (Co-Supervisor) & Ana Sofia Oliveira (Co-Supervisor)