Characterization of Chemical and Bacterial Compositions of Dairy Wastewaters

Abstract

The dairy industry produces large amounts of wastewater, including white and cleaning wastewater originating principally from rinsing and cleaning-in-place procedures. Their valorization into process water and non-fat milk solids, in the case of white wastewater, or the renewal of cleaning solutions could be achieved using pressure-driven membrane processes. However, it is crucial to determine the intrinsic characteristics of wastewaters, such as proximate composition and bacterial composition, to optimize their potential for valorization. Consequently, white and cleaning wastewaters were sampled from industrial-scale pasteurizers located in two different Canadian dairy processing plants. Bacterial profiles of dairy wastewaters were compared to those of tap waters, pasteurized skim milk and unused cleaning solutions. The results showed that the physicochemical characteristics as well as non-fat milk solids contents differed drastically between the two dairy plants due to different processing conditions. A molecular approach combining quantitative real-time polymerase chain reaction (qPCR) and metabarcoding was used to characterize the bacteria present in these solutions. The cleaning solutions did not contain sufficient genomic DNA for sequencing. In white wastewater, the bacterial contamination differed depending on the dairy plant (6.91 and 7.21 log10 16S gene copies/mL). Psychrotrophic Psychrobacter genus (50%) dominated white wastewater from plant A, whereas thermophilic Anoxybacillus genus (56%) was predominant in plant B wastewater. The use of cold or warm temperatures during the pasteurizer rinsing step in each dairy plant might explain this difference. The detailed characterization of dairy wastewaters described in this study is important for the dairy sector to clearly identify the challenges in implementing strategies for wastewater valorization.

High toxicity of agro‐industrial wastewater on aquatic fauna of a South American stream: Mortality of aquatic turtles and amphibian tadpoles as bioindicators of environmental health

“…These findings may be linked to wastewater from SCC. The untreated agroindustrial wastewater (e.g., dairy effluents) contains soluble organics, suspended solids, trace organics, large amounts of milk compounds such as casein and inorganic salts, detergents, and sanitizers, which are used for washing, and sodium hydroxide that produce high BOD and COD levels as previously demonstrated by Shete and Shinkar (2013) and Alalam et al (2021). The high organic load is quickly degraded because of the aquatic biota role; however, this leads to a decrease in dissolved oxygen and an increase in BOD (Elliott et al, 2001).…”

“…The rich organic composition of buttermilk represents a potential environmental problem for water pollution since it increases nutrients in aquatic systems such as phosphorus and nitrogen that can lead to eutrophication (Dhall et al, 2012; Jindal et al, 2004). Residuals from untreated effluents from dairy industries contain large amounts of milk compounds such as casein and inorganic salts, besides detergents and sanitizers used for washing and sodium hydroxide that could also contribute to the toxicity of this matrix and high BOD and COD levels (Alalam et al, 2021).…”

Research on the quality deterioration of UHT milk products during shelf life: core microorganisms and related characteristics

“…4f). Serratia are also common psychrophilic and pathogenic bacteria in milk, and ectoenzymes can be used to hydrolyze fat and proteins [36,37]; While Bacillus anaerobic was the dominant bacterium frequently detected in the wastewater of dairy plants [38]. The species composition of normal UHT milk (SZ) and quality deteriorated UHT milk (QY, WY) were analyzed at the phylum level.…”