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The milk processing industry is one of the world's staple industries, thus the treatment possibilities of dairy effluents have been attracting more and more attention. The purpose of the paper is to review contemporary research on dairy wastewater. The origin, categories, as well as liquid by-products and general indicators of real dairy wastewater are described. Different procedures applied for dairy wastewater management are summarised. Attention is focused on in-factory treatment technologies with the emphasis on biological processes. Aerobic and anaerobic methods with both their advantages and disadvantages are discussed in detail. Consecutive anaerobic and aerobic systems are analysed, too. Finally, future research niches are identified.

Milk-based products are essential to the human diet, with India contributing 23% of global milk production. Dairy industries generate large amounts of waste, including solid and liquid waste, which are treated using wetland, biological, and physico-chemical methods. In India, dairy sludge is effectively managed by converting it into fertilizers. If industrial solid and liquid dairy waste is not managed correctly, it will increase pollution and harm biodiversity. If the sludge is properly managed, there is potential to transform it into various value-added products, including biofuels, biomass, biofertilizers, bricks, struvite, fertilizer, etc. Consequently, this technical review’s focal topic includes information on dairy operations’ wastewater treatment methods, the viability of microalgal cultures in wastewater, dairy sludge management, the range of biological product recovery, and its impact on the environment.

In 2012 there were 63% fewer dairies in the United States than there were in 1997 as a result of conglomeration of the dairy industry into concentrated animal feeding operations at the expense of smaller farms. Today, 60% of all milk produced in the United States comes from 5% of the nation’s dairies (operations with ≥ 500 cows). Concentrated animal feeding operations are touted as economically efficient agricultural business models, hailed for their increased milk yields. Yet, with an average daily manure production of over 27 000 kg for a 500-head dairy farm, manure storage and disposal are serious management and environmental concerns. A common economical mode of manure disposal is application to nearby agricultural fields. However, a major concern with land application of dairy manure is the fate of manure-borne hormones, compounds considered chemicals of emerging concern, and the potential threat these hormones pose to humans and the environment. The fate of these chemicals in the soil environment is complicated by multiple edaphic variables including pH, mineralogy, organic matter, microbial activity, and redox status. Estrogens are sorbed by soil organic matter and transformed to nonbioactive, highly soluble conjugated forms or to metabolites that exhibit yet additional properties distinct from their parent compounds. However, deconjugation frequently occurs, regenerating endocrine-disrupting free estrogen compounds. It is challenging to fully understand the behavior and predict the fate of estrogenic compounds from dairy manure in soils because of variable and complex interactions with soil factors, as well as possible interactions among the different chemicals of emerging concern. This review focuses on the behavior of naturally occurring estrogen hormones present in dairy manure in the soil environment. Heightened understanding of the fate of these compounds in soil will enhance our ability to reduce their potential risks.

Anaerobic dairy waste treatment requires effective control to avoid long-chain fatty acid (LCFA) inhibitory effects on anaerobic microorganisms, especially methanogens. The hybrid anaerobic baffled reactor (HABR) can provide system stability, but more needs to be done to understand how the microbial communities underpinning the HABR compartments behave and respond. Thus, this study aimed to examine the HABR’s microbial community correlating its performance when subjected to an increase in organic loading rate (OLR) during simulated dairy wastewater treatment. Besides the elevation in OLR, the system could maintain a high COD removal efficiency, nearly to 91%, and elevate the methane production to 53%. Almost all of the organic matter removal occurred mainly in C1 and C2 compartments. The genera Methanosaeta, an acetoclastic methanogen, and Methanobacterium, a hydrogenotrophic methanogen, were the HABR’s dominant species. The most representative phylum found was Bacteroidetes (12–28%), Firmicutes (3–20%), Chloroflexi (4–26%), and Proteobacteria (4–14%). Species capable of syntrophic partnership with methanogens were also identified, belonging to the family of Syntrophomonadaceae and Syntrophaceae. Microorganisms able to perform the AD process as HA73, VadinCA02, T78, Longilinea, Clostridium, and Syntrophomonas were present in the HABR.

The application of chemical fertilizers to enhance crop production is a major concern due to associated environmental pollution and health hazards. Hence, there is an urgent need to develop an eco-friendly solution to improve crop production and promote sustainable agriculture simultaneously. Stevia rebaudiana is an important medicinal crop being substitute for sugar, superior flavor outline, extensive medicinal properties, and also of agronomic interest. In the present study, bacterium STJP isolated from the rhizospheric soil of S. rebaudiana and identified as Bacillus safensis on the basis of 16S rRNA gene sequencing, showed good amount of zinc (4.4 mg/L) and potassium (5.4 mg/L) solubilization. Paneer-whey (a dairy waste) based bioformulation (P-WBF) was developed utilizing isolate B. safensis STJP (accession number NAIMCC TB-2833) and inspected for the quality and ability to enhance the growth, nutrients uptake, and stevioside content in S. rebaudiana. The application of P-WBF displayed a significantly higher concentration (153.12%) of stevioside in S. rebaudiana as compared to control. P-WBF treated Stevia plants showed significantly higher fresh and dry weight as well (as compared to control). Further, enhancement of phosphorous, nitrogen, potassium, and zinc uptake in plant tissue was also recorded by application of P-WBF. This study suggests the use of P-WBF based biofertilizer using B. safensis STJP to increase stevioside content in Stevia plant by a nutrient(s) linked mechanism. This novel approach can also be beneficial for utilization of a dairy waste in preparation of bioformulation and, for enhancement of crop yield by an ecofriendly manner leading to sustainable agriculture.Graphic abstract

Due to the high volume of wastewater produced from dairy factories, it is necessary to integrate a water recovery process with the treatment plant. Today, bipolar membrane electrodialysis units (BMEUs) are increasingly developed for wastewater treatment and reutilizing. This article aims to develop and evaluate (technical and cost analyses) a combined BMEU/batch reverse osmosis unit (BROU) process for the recovery of chemicals and water from the dairy wastewater plant. The combined BROU/BMEU process is able to simultaneously produce water and strong base-acid, and reduce power consumption due to the injection of concentrated feed flow into the BMEU. A comprehensive comparative analysis on the performances of two combined and stand-alone BMEU configurations are developed. The proposed combined technology for dairy factory wastewater treatment is designed on a new structure and configuration that can address superior cost analysis compared to similar technologies. Further, the optimal values of permeate flux and current density as two vital and influencing parameters on the performance of the studied dairy wastewater treatment process were calculated and discussed. From the outcomes, the total cost of production in the combined configuration has been reduced by approximately 26% compared to the stand-alone configuration. Increasing the feed concentration rate using the batch reverse osmosis process for the dairy wastewater treatment process can be an ideal solution from an economic point of view. Moreover, point (current density, feed concentration rate, total unit cost) = 328.9 , 7 , 14.37 can be considered as an optimal point for the economic performance of the studied wastewater treatment process.

Background Biofilm-based microalgal growth was determined as functions of organic chemical loading and water temperature utilizing dairy wastewater from a full-scale dairy farm. The dairy industry is a significant source of wastewater worldwide that could provide an inexpensive and nutrient rich feedstock for the cultivation of algae biomass for use in downstream processing of animal feed and aquaculture applications. Algal biomass was cultivated using a Rotating Algal Biofilm Reactor (RABR) system. The RABR is a biofilm-based technology that has been designed and used to remediate municipal wastewater and was applied to treat dairy wastewater through nutrient uptake, and simultaneously provide biomass for the production of renewable bioproducts. Results Aerial algal biofilm growth rates in dairy wastewater at 7 and 27 °C temperatures were shown to be 4.55 ± 0.17 g/m 2 -day and 7.57 ± 1.12 g/m 2 -day ash free dry weight (AFDW), respectively. Analysis of Variance (ANOVA) calculations indicated that both an increase in temperature of the wastewater and an increase in the level of organic carbon, from 300 to 1200 mg L -1 , contributed significantly to an increase in the rate of biomass growth in the system. However, ANOVA results indicated that the interaction of temperature and organic carbon content was not significantly related to the biofilm-based growth rate. Conclusion A microalgae-based biofilm reactor was successfully used to treat turbid dairy wastewater. Temperature and organic carbon concentration had a statistically significant effect on algae-based biofilm productivity and treatment of dairy wastewater. The relationships between temperature, TOC, and productivity developed in this study may be used in the design and assessment of wastewater remediation systems and biomass production systems utilizing algae-based biofilm reactors for treating dairy wastes.

This research focuses on addressing the environmental challenges posed by dairy wastewater problems using advanced oxidation processes (AOP). This study uses a composite of MIL-88 A(Fe)/C with an electro-Fenton process to mitigate the organic pollutants in dairy wastewater. The MIL-88 A(Fe)/C composite is synthesized by combining MIL88-A with carbon in a hydrothermal process, and its morphological characterization was investigated by spectroscopy and microscopy methods. The parameters of pH, time, composite concentration, and oxidizer concentration were optimized by the response surface method (RSM). In all experiments, the electrode distance was 3 cm and the current density was 9 A/m 2 . A quadratic model was fitted to the data. Comparison of adjusted R 2 with predicted R 2 validated the model. Kinetic studies revealed it followed pseudo-second-order behavior. The optimum conditions for reducing COD in the electro-Fenton process were pH 7.0, contact time 102.6 min, catalyst concentration MIL-88 A(Fe)/C 0.5 g/L, and oxidizing concentration of Na 2 S 2 O 8 0.026 M. Under these conditions, COD removal efficiency from the Isfahan Pegah Dairy factory’s wastewater was statistically equal to 86.6% and experimentally equal to 89%. The results of the electro-Fenton process using MIL-88 A(Fe)/C composite, low-cost graphite, and titanium electrodes were competitive and promising compared to previous research on the Wastewater of Dairy Industries.

The objective of the research presented in this Research Communication was to access the environmental impact of the Latvian dairy industries. Site visits and interviews at Latvian dairy processing companies were done in order to collect site-specific data. This includes the turnover of the dairy industries, production, quality of water in various industrial processes, the flow and capacity of the sewage including their characteristic, existing practices and measures for wastewater management. The results showed that dairy industries in Latvia generated in total approximately 2263 × 103 m3 wastewater in the year 2019. The Latvian dairy effluents were characterized with high chemical oxygen demand (COD), biological oxygen demand (BOD) and total solids (TS). Few dairy plants had pre-treatment facilities for removal of contaminants, and many lacked onsite treatment technologies. Most facilities discharged dairy wastewater to municipal wastewater treatment plants. The current study gives insight into the Latvian dairy industries, their effluent management and pollution at Gulf of Riga due to wastewater discharge.

Nutrient-rich dairy wastewater (DWW) is an excellent growing medium for microbes. Their antimicrobial resistance (AMR) genes and pathogenic roles remain in the DWW and even multiply in environmental settings, in contrast to many chemical toxins that break down over time. Necessary steps and standardized techniques for tracking AMR in DWW samples are desperately needed. In this context, a DWW sample was evaluated to assess the necessity of remediation and develop a suitable treatment technique. Physicochemical characterizations of the sample showed an elevated level of pollutants like proteins, fats, and carbohydrates that led to the water pollution and microbial diversity (e.g., 36 phyla, 72 classes, 111 orders, 168 families, 275 genera, and 347 species). The Shannon and Simpson indices showed that the DWW sample had a high level of microbial diversity of a few species. The gene ontology (GO) analysis revealed the functional categories with 2795 genes belonging to 11 virulence categories. Most of the identified AMR genes belonged to beta-lactamase, and the majority of them were linked to Escherichia coli , Mycobacterium tuberculosis , Staphylococcus aureus , Klebsiella pneumoniae , Pseudomonas aeruginosa , Enterobacter cloacae , etc. The major bacterial phyla carrying AMR genes included Firmicutes (36%), Proteobacteria (31%), Actinobacteria (21%), and Bacteroidetes (5%).