Enhanced fat degradation following the addition of a Pseudomonas species to a bioaugmentation product used in grease traps

Tackling fat, oil, and grease (FOG) build-up in sewers: Insights into deposit formation and sustainable in-sewer management techniques

The increasing global demand for fatty products, population growth, and the expansion of food service establishments (FSEs) present significant challenges for the wastewater industry. This is often due to the build-up of fat, oil and grease (FOG) in sewers, which reduces capacity and leads to sanitary sewer overflows. It is crucial to develop economic and sustainable in-sewer FOG management techniques to minimise maintenance costs and service disruptions caused by the removal of FOG deposits from sewers. This study aims to understand the process of FOG deposit formation in both concrete and non-concrete sewers. Compared to fresh cooking oil, disposal of used cooking oil in households and FSE sinks results in the formation of highly adhesive and viscous FOG deposits. This occurs due to hydrolysis during frying, which increases the concentration of fatty acids, particularly palmitic acid, in the used cooking oil. Furthermore, metal ions from food waste, wastewater, and dishwashing detergents contribute to the saponification and aggregation reactions which cause FOG deposition in both concrete and non-concrete sewers. However, the leaching of Ca2+ ions exacerbates FOG deposition in cement-concrete sewers. The article concludes by suggesting future research perspectives and proposes implementation strategies for microbially induced concrete corrosion (MICC) control to manage FOG deposition in sewers. One such strategy involves applying superhydrophobic coating materials with low surface free energy and high surface roughness to the interior surfaces of the sewer. This approach would help repel wastewater carrying FOG deposit components, potentially disrupting the interaction between FOG components, and reducing the adhesion of FOG deposits to sewer surfaces.

Understanding the properties of fat, oil, and grease and their removal using grease interceptors

Treatment of wastewater with high levels of fat, oil, and grease (FOG), produced by the growing number (annually 2%) of food service establishments (FSEs), is a major concern for water utilities. About 30-40% of sewer blockages are caused primarily by the formation of FOG deposits in sewer pipes, and an annual additional maintenance cost is required for sewer management. To manage FOG deposition, FSEs are required to recover the FOG at the point of generation by installing grease interceptors (GIs) before release to the sewer system. The successful control of FOG deposition is largely dependent on clear understanding of its complex properties, pre-treatment processes, deposition mechanism and public awareness. The objective of this study is to provide a comprehensive understanding of the physicochemical properties of FOG, including particle size distribution and their removal efficiencies by existing GIs. Nowadays, generation of FOG particles of ≤45 µm is increasing because of the increasing use of automatic dishwashers. Current hybrid processes which comprise pre-treatment prior to GI use are ineffective since they are unable to completely remove particle sizes of ≤45 µm. Hence, there is potential for these particles to be released into the sewer system and eventually cause blockages. This critical review discusses the characteristics of effluents, including the particle size distributions generated from automatic dishwashers and handwash sinks. It concludes by providing some case studies and a perspective of the future opportunities to develop a novel GI process integrated with pre-treatment to remove particles of all sizes, including colloidal particles.

Synergetic degradation of waste oil by constructed bacterial consortium for rapid in-situ reduction of kitchen waste

Traditional composting of kitchen waste (KW) is cost- and time-intensive, requiring procedures of collection, transport and composing. Consequently, the direct in-situ reduction of KW via treatment at the point of collection is gaining increasing attention. However, high oil content of KW causes separation and degradation issues due to its low bioavailability and the hydrophobicity, and therefore greatly limiting the direct application of in-situ methods for mass reduction. To overcome this, a bacterial consortium of Pseudomonas putida and Bacillus amyloliquefaciens was constructed, which exhibited a synergistically improved oil degrading ability for lipase-catalyzed hydrolysis, fatty acids β-oxidation, biosurfactant production and surface tension reduction, and the degradation ratio reached 58.96% within 48 h when the initial KW oil concentration was 8.0%. The in-situ aerobic digestion of KW was further performed in a 20-L stirred-tank reactor, the content of KW oil (34.72 ± 2.05% of total solids, w/w) was rapidly decreased with a simultaneous increase in both lipase activity and in microbial cell numbers, and the degradation ratio reached 57.38%. The synergetic effect of the two strains including B. amyloliquefaciens and P. putida promoted the decomposition process of KW oil, which also paved the way for an efficient degradation strategy to support the application potential of in-situ microbial reduction of KW.

Integrated selection and identification of bacteria from polluted sites for biodegradation of lipids

Wastewater treatment plants face major social concern towards removal of problematic pollutants such as fat oils and grease (FOG). In this context, the main objective of the present work was to select natural bacterial isolates from different polluted sites and evaluate them comparatively to isolates from commercial products, for improved bioremediation strategies and bioaugmentation. In total, 196 isolates were analysed for genomic diversity by two PCR-fingerprinting methods and screened for biodegradation potential with pollutants as sole carbon source. The net area under curve (NAUC) was used for preliminary evaluation of growth ability in M9 medium supplemented with oleic acid and triolein. A principal component analysis of all NAUC data showed that natural isolates presented higher overall biodegradation ability and enabled the selection of 11 natural isolates for lipid degradation assays. Selected isolates were identified by 16S rRNA gene sequencing as members of genera with previously described degradative strains, namely, Acinetobacter (1), Aeromonas (2), Bacillus (1), Pseudomonas (1) and Staphylococcus (6). Best biodegradation results in 7-days assay of FOG content removal were 37.9% for oleic acid and 19.1% for triolein by an Aeromonas sp. isolate and a Staphylococcus cohnii isolate, respectively. A respirometry approach confirmed their higher oxygen uptake rates, although longer adaptation phases where required by the Aeromonas sp. isolate. Consequently, these isolates showed great potential for future bioaugmentation products, to promote FOG degradation, for both in situ and ex situ approaches.

Accelerated Rhodamine B removal by enlarged anode electric biological (EAEB) with electro-biological particle electrode (EPE) made from steel converter slag (SCS)

Electro-biological particle electrode (EPE) made from steel converter slag (SCS) was used as a particle electrode in an enlarged anode electric biological (EAEB) reactor for Rhodamine B (RhB) wastewater treatment, and its purification performance and microbial community were examined. The results revealed that (1) the EAEB reactor showed much higher average removal rates of RhB, COD and NH₄⁺-N, i.e. 91.68%, 87.63%, and 90.54%, which meant an increase by 59.86%, 20.48%, and 14.22%, respectively, compared with BAF; (2) The optimum current intensity (CI) for simultaneously removing RhB, COD and NH₄⁺-N in the EAEB reactor was at 1.00 A; and (3)Methylophilus, Aeromonas, Pseudomonas, Pelomonas and Zoogloea accounted for the main bacterial community in EAEB. Therefore, the EAEB reactor with EPE produced from steel converter slag (SCS) was suitable to simultaneously remove RhB, COD and NH₄⁺-N.