Abstract
Polyhydroxyalkanoates (PHA) are biodegradable polymers that can be intracellularly produced by microorganisms valorizing organic-rich wastes. In the present study, a PHA production system was fed with mussel cooker wastewater after acidogenic fermentation. Besides low pH (4.0 ± 0.3) and high salt (21.7 ± 2.9 g NaCl/L) concentrations, this wastewater also contained nitrogen concentrations (0.8 ± 0.1 g N/L), which were previously reported to be a challenge to the PHA accumulating bacteria enrichment. Bacteria with a PHA storage capacity were selected in an enrichment sequencing batch reactor (SBR) after 60 days of operation. The enriched mixed microbial culture (MMC) was mainly formed by microorganisms from phylum Bacteroidetes, and genera Azoarcus, Comamonas and Thauera from phylum Proteobacteria. The MMC was able to accumulate up to 25 wt% of PHA that was mainly limited by the wastewater nitrogen content, which promoted biomass growth instead of PHA accumulation. Indeed, when the presence of nutrient was limited, PHA stored in the accumulation reactor increased to up to 40.9 wt%. This work demonstrated the feasibility of the enrichment of a MMC with a PHA storage ability valorizing the fish-canning industrial wastewater at low pH, which is generally difficult to treat in wastewater treatment plants.
Highlights
Fish and seafood processing industries consume vast volumes of water and, generate large amounts of wastewater with high organic matter, nutrients and salt concentrations
The performance of the enrichment sequencing batch reactor (SBR) was monitored by the feast phase length (Figure 1), which was measured by the change in the dissolved oxygen (DO) concentration profile
Dionisi et al [31] found that the selection of microorganisms with storage response takes place when the feast phase length is lower than approximately 20% of the overall length of the cycle
Summary
Fish and seafood processing industries consume vast volumes of water and, generate large amounts of wastewater with high organic matter, nutrients and salt concentrations. Méndez et al [6] achieved, in an anaerobic digester, a COD removal efficiency of 80% treating effluents generated in a factory processing different fish products with high salinity (up to 15 g Cl−/L). There are fish and seafood canning facilities that treat their effluents by only applying physical-chemical treatment steps to remove grease and solids and the wastewater is discharged to the municipal WWTP to be polished. Fish and seafood industry wastes (as organic-rich streams) can be valorized to produce volatile fatty acids (VFA) suitable for use as a chemical platform to obtain other compounds such as biopolymers [8,9]
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