Meat Processing Wastewater Research Articles

Full-scale study on high-rate low-temperature anaerobic digestion of agro-food wastewater: process performances and microbial community.

The fast-growing global population has led to a substantial increase in food production, which generates large volumes of wastewater during the process. Despite most industrial wastewater being discharged at lower ambient temperatures (<20 °C), majority of the high-rate anaerobic reactors are operated at mesophilic temperatures (>30 °C). High-rate low-temperature anaerobic digestion (LtAD) has proven successful in treating industrial wastewater both at laboratory and pilot scales, boasting efficient organic removal and biogas production. In this study, we demonstrated the feasibility of two full-scale high-rate LtAD bioreactors treating meat processing and dairy wastewater, and the microbial communities in both reactors were examined. Both reactors exhibited rapid start-up, achieving considerable chemical oxygen demand (COD) removal efficiencies (total COD removal >80%) and generating high-quality biogas (CH4% in biogas >75%). Long-term operations (6-12 months) underscored the robustness of LtAD bioreactors even during winter periods (average temperature <12 °C), as evidenced by sustained high COD removal rates (total COD removal >80%). The stable performance was underpinned by a resilient microbial community comprising active acetoclastic methanogens, hydrolytic, and fermentative bacteria. These findings underscore the feasibility of high-rate low-temperature anaerobic wastewater treatment, offering promising solutions to the zero-emission wastewater treatment challenge.

EFFECT OF DAIRY AND MEAT WASTEWATER IRRIGATION ON SEEDLING GROWTH

Milk and meat processing industries release large quantities of nutrient-rich wastewater with organic compounds (proteins, fats, carbohydrates) in high concentrations. Reusing and recycling this biodegradable wastewater for crop irrigation could be a sustainable solution once the phytotoxic effects of wastewater on crops have been investigated. Therefore, the aim of this study was to evaluate the effects of milk and meat processing wastewaters on germination percentage, seed vigour indices, the seedling tolerance index and the phytotoxicity index of pea (Pisum sativum L.), sugar maize (Zea mays saccharata), purslane (Portulaca oleracea), wheat (Triticum aestivum) and red spinach (Amaranthus dubius). The two wastewater types were collected at the inlet of the city’s sewage system and analysed to determine their physicochemical and microbiological characteristics. The seeds of all five plant species were irrigated with untreated wastewater effluents. The highest - germination percentages were obtained for wheat (92%) and the lowest for red spinach (2.5%). Wheat, purslane, pea and red spinach samples irrigated with meat processing wastewater had higher germination percentages than samples irrigated with dairy wastewater. A higher phytotoxicity was observed for sugar maize, followed by red spinach irrigated with both types of wastewater. Future investigation into the effects of effluent dilution on these types of plants is recommended.

Characterization of Low-Volume Meat Processing Wastewater and Impact of Facility Factors

Low-volume meat processing facilities often rely on decentralized wastewater treatment due to cost constraints and the lack of access to centralized treatment. Improved characterization of these facilities’ wastewater is crucial for meeting local groundwater discharge permits. This study also directly correlates treatment systems and facility characteristics to the results of the characterization. The total nitrogen (TN), biochemical oxygen demand (BOD), and phosphorus (P) reductions ranged from −15% to 83%, 43% to 95%, and −75% to 62%, respectively. Slaughtering and smoking were found to significantly increase nutrient concentrations. The average TN leaving the slaughterhouses and processing-only facilities was 519 mg/L-N and 154 mg/L-N, respectively. The average BOD produced by the slaughterhouses and processors was 3002 mg/L and 1660 mg/L, respectively. Filtration was found to reduce BOD, chemical oxygen demand (COD), and trace metals. Aeration in a treatment lagoon was found to significantly reduce BOD, COD, and N compounds. The results indicate that even simple decentralized wastewater treatment systems, combined with facility management practices, can substantially reduce permitted wastewater characteristics. The facility with the best BOD removal had an effluent value of 71.3 mg/L, representing a 96% reduction. The facility with the best TN removal had an effluent value of 20 mg/L, representing a 92% reduction prior to discharge.

Influence of C/N ratio on microalgae-bacteria joint culture: Treatment performance and phytoplankton dynamics in mixed wastewaters

Microalgae biotechnology may represent a potential solution for minimizing the impacts of food industry activities, acting in bioremediation of wastewaters, and producing value-added biomass. Therefore, this work aimed to evaluate the biomass production and treatment performance of 5 culture media obtained by mixing brewery and meat processing wastewaters and to test the effects of their different C/N ratios. Cultivation media under optimal conditions (C/N = 6), deficit (C/N < 6), and excess (C/N > 6) of carbon were evaluated. Microalgae biomass and total biomass have adapted to all conditions, revealing resilience and symbiosis balance. Although, treatment performance was statistically distinct (p > 0.1). Total carbon, nitrogen, and phosphorus removals were influenced by nutrient availability. Biomass growth removed total carbon, total nitrogen, and total phosphorus from the culture medium at a rate of 62 % (C/N ≥ 7.4), 59 % (C/N = 4.1), and 58 % (C/N = 4.1), respectively.

Optimization of bioenergy generation and chemical oxygen demand reduction in dual-chamber microbial fuel cells using active soil microbes

This study focused on the optimization of a dual-chamber microbial fuel cell (MFC) system using carbon fiber brush and titanium electrodes, meat processing wastewater as substrate, and active soil microbes as biocatalyst. Significant findings revealed promising results on the MFC performance. The active soil microbes contain viable bacteria that worked effectively in the anode chambers. Peak open-circuit voltages (OCV) of the MFCs were as high as 1.05 V using titanium mesh and 1.03 V using carbon fiber brush. In closed-circuit conditions, the current obtained were 1.04 mA and 1.38 mA, and the power densities were 1.22 Wm−2 and 0.34 Wm−2, correspondingly. The power densities were normalized based on the surface areas of the anodes. The bioenergy generation profiles also revealed the MFCs can produce peak potentials of 30.109 kJ and 19.415 kJ using carbon fiber brush and titanium mesh, respectively. Furthermore, the results showed that the reduction in chemical oxygen demand (COD) was highest at 24.32 percent using carbon brush and lowest at 13.34 percent using titanium mesh electrodes.

Utilization of lactobacillus fermented proteins from meat processing wastewaters as a dietary protein source in poultry feed.

The present study aimed to evaluate the impact of fermented meat processing wastewater protein hydrolysate (FWMPH) prepared by Pediococcus lolii fermentation as an alternative protein source on growth performance, serum biochemistry, and hematological parameters of broiler chicks. FWMPH exhibited antioxidant, anti-angiotensin converting enzyme (ACE), and antimicrobial properties. A total of 60 one-day-old Vencobb broiler chicks were divided into five dietary groups on day 8 and a feeding trial was performed for 48days. Diets were prepared by replacing soya protein concentrate (SPC) at different levels of FWMPH as the protein source. These diets were denoted as SPSD (100% SPC), FMP-25 (25% FWMPH + 75% SPC), FMP-50 (50% FWMPH + 50% SPC), FMP-75 (75% FWMPH + 25% SPC), and FMP-100 (100% FWMPH). FMP-25 and FMP-100 diet group broiler chicks showed the highest and lowest feed consumption (P < 0.05), respectively. However, the highest body weight gain (1506.08 ± 52.52g) was observed in FMP-75 diet-fed chicks (P < 0.05). Furthermore, FMP-75 chicks displayed better feed conversion ratio (1.96), feed efficiency ratio (0.51), and protein efficiency ratio (2.32) values than other diet group chicks (P < 0.05), implying that the FMP-75 diet had better effect on the broiler growth. Also, the FMP-75 diet chicks showed better hematological values, serum biochemical parameters revealed no negative effect upon FWMPH consumption, and no pathological signs were observed in the histopathological examination as compared to the SPSD diet group (P < 0.05). Hence, the results could be helpful in the application of FWMPH at 75% level in the poultry feed as a potential protein ingredient in the countries looking for local feed protein products as soya bean meal replacement.

Efluenti iz industrijske prerade hrane životinjskog porekla kao medijumi za proizvodnju biokontrolnih agenasa

Intensive food production to feed the growing human population requires significant material and energy resources, simultaneously generating large amounts of waste, whose treatment adds an additional cost to the overall production process. Wastewaters arising from meat and dairy processing industries contain large amounts of organic and inorganic nutrients, which present a heavy environmental burden, but, on the other hand, could serve as nutrient sources for microbial growth. The aim of this study was to investigate the suitability of meat processing wastewater and whey from the dairy industry as media for the growth of biocontrol strain Bacillus velezensis IP22. Both waste-based media have contributed to antibacterial and antifungal activity to a similar degree, with highly comparable inhibition zone diameters against Xanthomonas campestris, Xanthomonas euvesicatoria and Aspergillus flavus. Furthermore, biocontrol activity of the cultivation broths obtained using the waste-based media was slightly lower compared to the nutrient broth medium, suggesting the possibility to replace the expensive chemically defined medium with a complex medium alternative. This approach based on circular economy principles promotes responsible resource utilization through the reuse of food industry effluents for the production of value value-added products, opening a chapter of possibilities to establish an industrial symbiosis network between companies in different industry branches.

Enhanced flow-through electro-Fenton process based on rGO aerogel cathode: Essential role of sodium tetrapolyphosphate

As a promising advanced oxidation process, electro-Fenton (EF) technology could in-situ generate H2O2 through 2e- oxygen reduction reaction (ORR), and then activate H2O2 into reactive oxygen species to degrade the organic pollutants in wastewater. However, its practical application is limited by the sluggish ORR kinetics and acidic condition (pH < 3), which requires external addition of acids, ferrous salts (FeII) or even H2O2. To improve the efficiency of wastewater treatment, targeted development on EF technology based on specific application scenario is also critical. In this contribution, a flow through EF system was developed to remove the antibiotic pollutants in the meat processing wastewater, where the EF process was significantly enhanced by the reduced graphene oxides (rGO) aerogel cathode and the presence of polyphosphates (PPs). The interconnected 3D porous configuration of rGO aerogel with abundant oxygen functional groups greatly facilitated the mass and electron transfer during the flow-through EF process. Meanwhile, the formation of PPs film on the surface of sacrificial iron anode ensured continuous releasing of FeII under near-neutral condition without rusting, and the generation of FeII-PPs complexes effectively compensated the production of H2O2 via the pathway of molecular oxygen activation. Moreover, 99.9% of phosphorus can be recycled and reused in the flow-through EF system by coupling the nanofiltration technology, enabling efficient removal of antibiotics and utilization of PPs in the wastewater.

Improving CH4/O2 energy ratio of meat processing wastewater treatment systems through micro-sieving

ABSTRACT Micro-sieving is an effective way to prevent organic pollutants enter the main biological process and reduce aeration intensity and sludge production. However, few researchers quantified the effect of micro-sieving on meat processing wastewater treatment. The current study developed Excel-based models to compare the energy consumption and production of historical, conventional and innovative systems. Historical and conventional systems employ activated sludge (AS), nitrification, and denitrification as the main biological processes. Innovative systems are designed by using up-flow anaerobic sludge blanket (UASB) and partial nitrification/Anammox (PN/A) as the main treatment processes. Results show that the CH4/O2 energy ratios of the innovative treatment system are as high as 10 times of the historical and conventional systems. Therefore, innovative system can achieve electrical self-sufficiency. Micro-sieving reduces 5% of aeration demand. Furthermore, the impact of micro-sieving on the innovative treatment systemis assessed by cost-benefit analysis. System with micro-sieving has the shortest payback time of 2.1 years and reduces cost of the innovative treatment system. An excel-based model was developed to quantify the impact of micro-sieving on energy and cost of innovative treatment system, thereby providing a valuable reference for future sustainable engineering design of meat processing wastewater treatment.

Primary Sludge from Dairy and Meat Processing Wastewater and Waste from Biomass Enzymatic Hydrolysis as Resources in Anaerobic Digestion and Co-Digestion Supplemented with Biodegradable Surfactants as Process Enhancers

Incorporation of various alternative resources as co-digestion substrates aids to reduce the consumption of agricultural crops for biogas production. However, the efficiency and limitations of these co-substrates is still not fully understood. Use of biomass waste remaining after enzymatic hydrolysis for high value chemical fermentation, meat processing and dairy wastewater primary sludge as co-substrates in an agricultural resource anaerobic digestion plant is tackled within this study. The results showed that anionic surfactants (&lt;200 ppm) can be used to improve fat, oil and grease (FOG) solubility in water and, at the same time, enhance the biomethane potential of FOG-containing sludge by increasing it from 1374.5 to 1765 mLCH4/gVS for meat processing wastewater primary sludge, and from 534 to 740 mLCH4/gVS for dairy wastewater primary sludge, when agricultural digestate is used as a substrate and sludge loading is not more than 10% from the volatile solids loaded. At the same time, only 549.7 mLCH4/gVS was produced as 30-day BMP when 5% biomass hydrolysis waste was used. Biomass hydrolysis waste co-digestion with primary sludge from dairy and meat processing wastewaters has an antigenic effect, and separate substrate anaerobic digestion gave a better results, thus, showing that excessive combination of various waste resources can be inhibitory for biogas production and the appropriate substrate selection and combination is a technical challenge for the biogas industry.

Nutrients elimination from meat processing wastewater using Scenedesmus sp.; optimizations; artificial neural network and kinetics models

The potential of an algae-based system as an environmentally friendly and low-cost water treatment method to eliminate contaminants from water bodies has been considered. The purpose of this research was to see how effective Scenedesmus sp is in eliminating nutrients from meat processing wastewater (MPWW) throughout the phycoremediation process. Response surface methodology (RSM) and an artificial neural network (ANN) model were applied to improve the inactivation process as a function of cell concentrations (3–7 log 10 CFU/mL) and time (1–13 days). At 10 3 to 10 7 cell/mL of Scenedesmus sp., phycoremediation was carried out at atmospheric temperature (28 ± 2 °C, ± 2500lux for 12:12 h of light/dark and pH 8). The findings documented 73.76% as the highest removal efficacy of total nitrogen (TN) and 77.85% of total phosphorus (TP), 75.40% of ammonia nitrogen (NH 4 -H), 77.88% of orthophosphate (PO 4 3 − ), and 64.97% of chemical oxygen demand (COD). The ANN revealed that both factors contribute significantly to the nutrient removal process. The batch kinetic coefficients of NH 4 -H removal were K m = 40 . 10 mg/L and k = 1 . 43 mg mg − 1 Chl a d −1 . Meanwhile, for PO 4 3 − , 1.07 mg mg − 1 Chl a d −1 , as well as 42.80 mg/L, were obtained. The NH4-N yield coefficient of NH 4 -N was Y n = 0 . 0192 mg Chl a mg − 1 while PO 4 3 − was equal to Y p = 0 . 0409 mg Chl a mg − 1 . These findings indicated successful use of Scenedesmus sp. for efficient pollutant removal from meat processing wastewater plants.

Multi response surface optimization, Pareto analysis and kinetics study of microalgal post-treatment systems

ABSTRACT High concentrations of nutrients are observed in the effluent of different wastewater treatment plants, while additional costs of post-treatment systems and low-value sludge are the main reasons for releasing such effluents. The present study aims to introduce an increased procedure for simultaneous nutrient recovery and biomass production using an algae-based post-treatment technique. The procedure has been utilized by two well-known strains (Scenedesmus dimorphus and Chlorella vulgaris) cultivated in different N/P ratios (16, 62, and 108) and trace metals (0, 50%, and 100%) in a synthetic meat processing wastewater as a model to investigate effects of the factors on microalgal cultivation and nutrient removal. Pareto statistical analysis and Multi Response Surface methodology were applied to determine the priority of factors and their optimum values, respectively. The unbalanced N/P ratio and lack of trace metals were introduced as two main reasons for the significant decrease of about 60% and 120% in nutrient removal and biomass production. The optimized procedure resulted in significant increases in the removal efficiencies where 90%, 83%, and 65% were achieved for ammonium, nitrate, and phosphate, respectively. Moreover, a 72% increase in biomass production was reported in the optimal points. The results of the Pareto analysis highlighted the significant superiority (about two times) of the trace metals in removal efficiencies. Finally, experimental data has also been modelled by Verhulst logistic model that successfully described the microalgae growth. This procedure showed promising results of microalgal systems to supersede the conventional post-treatment systems.

Intensified biogas upgrading via various wastewater using microchannel

In this article, several ideas have been proposed for CO2 separation and biogas upgrading using industrial wastewater. Synthetic gas (60% CH4, 40% CO2) has been upgrading in atmospheric pressure in a T-shaped microchannel using municipal, meat processing, water distillation, dairy, caustic, and fish pond wastewater. The municipal, fish pond, and meat processing wastewater contain ammonia, while dairy, and water distillation wastewater contains Ca2+, and Mg2+. Also, the caustic refinery wastewater contains NaOH, with higher alkalinity for CO2 separation. The effect of temperature, gas, and liquid flow rate were investigated. RSM analysis provided a function of three dependent variables of quadratic model for prediction of responses (CO2 removal efficiency and total mass transfer in gas phase) by each absorbent, and all models were meaningful. In addition, given that all R2 values were greater than 0.94, it was indicated that experimental values for removal of CO2 and mass transfer coefficient are favorably consistent with the values of the model. Maximum CO2 absorption was obtained at 30°C, liquid flow rate of 150 mL/hr, and biogas flow rate of 50 mL/min. According to the results obtained for mass transfer coefficient, these coefficients are at least 5 to 22 times greater than mass transfer coefficient in chemical absorption in normal absorption towers, such as packed towers.

H2S, MeSH, and NH3 emissions from activated sludge: An insight towards sludge characteristics and microbial mechanisms

The present study investigated the odor emission potential of activated sludge through comprehensive assessment for physicochemical properties and bacterial profile of sludge. Three types of sludges from wastewater treatment plants treating slaughterhouse (SWTP), meat processing (MWTP) and domestic wastewater (DWTP) were used based on distinct morphological features which were speculated to impact odor generation. Total element S in the SWTP sludge with relatively more disintegrated cellular debris exhibited higher level than that in the MWTP and DWTP sludge, while the emitted odorants (hydrogen sulfide and methyl mercaptan) showed the opposite patterns (i.e., the lowest level for the SWTP sludge). Nitrifying bacteria was only detected in the SWTP sludge, which was well in line with abundant nitrate in the corresponding aeration tank. Principal component analysis indicated that the potential of the odor emission from the sludge had strong correlations with dehydrogenase activity, and nitrate, which implies that these parameters may serve as referring indices for evaluating the potential of odor emission of sludge or treated product.

Application of alginate immobilized microalgae in treating real food industrial wastewater and design of annular photobioreactor: A proof-of-concept study

Microalgae immobilization was widely studied to address the challenge of algal cells harvesting, however, its stability and efficiency in treating real food industrial wastewater has not been well studied. In this study, microalgae were co-immobilized with sludge bacteria in alginate beads for treatment of real meat processing wastewater and an annular photobioreactor was designed to facilitate efficient light transmission at high beads-to-wastewater ratios. Results showed that increasing alginate mixture from 1.25% to 2.00% (w/v) extended beads stability in real wastewater from three to seven days. When beads were suspended in wastewater the overshading effect at beads-to-wastewater ratio of 20% (v/v) was significant and average algal growth (0.17 mg/bead) was lower than 2% (0.46 mg/bead) and 5% (0.36 mg/bead). Nevertheless, the ratio of 20% (v/v) was preferred as the higher beads count may compensate the disadvantage, however, the light transmission efficiency needed to be improved. The effect of environmental temperature indicated that at 37 °C beads started rupturing after three-days treatment due to the excessive growth of immobilized microorganisms. In comparison with suspended photobioreactor, in improved annular photobioreactor algal growth increased from 1412.6 to 3191.0 mg/L and removal of chemical oxygen demand (COD) and total nitrogen (TN) were improved from 78.5 to 82.9% and from 68.5 to 84.4% respectively with 89.4% total phosphate (PO43−) being removed. By the end of treatment, 135.9 mg/L TN and 99.2 mg/L total PO43− were removed and it was speculated that most of nitrogen and phosphorus were removed by algal assimilation rather than the physical adsorption of alginate gel. Findings of this study provided directions for the application of immobilized microalgae in the real world.

Application of proteins from different meat processing wastewater streams as a dietary protein source in animal feed

The present study aimed to investigate the protein quality indices of meat processing wastewaters protein hydrolysate (FWPH) obtained by Pediococcus lolii fermentation using a rat bioassay. Different diets namely, SD (100% casein), F50 (50% FWPH+50% casein), F75 (75% FWPH+25% casein), and F100 (100% FWPH) were formulated and fed to 28 days old albino male Wistar rats (6 rats each group). SD and F50 group rats showed higher feed and protein intake among all diet group rats (P < 0.05). However, the highest body weight gain (142.16 ± 2.84 g) was noticed in the rats fed with the F50 diet (P < 0.05). F50 group rats presented better feed conversion ratio (FCR), feed efficiency ratio (FER), and protein efficiency ratio (PER) values as compared to other diet group counterparts (P < 0.05). Furthermore, no differences in values of urine, haematological, and serum biochemical parameters were observed in SD and F50 group rats (P > 0.05). However, haematological and serum biochemical parameters were slightly elevated in F100 group rats. F50 group rats presented the higher superoxide dismutase (SOD) and catalase (CAT) activities among all the diet groups (P < 0.05). Relative organ weights, serum glutamic pyruvic transaminase (SGPT), serum glutamic oxaloacetic transaminase (SGOT), and alkaline phosphatase (ALP) activities of F50 group rats were found similar to SD rats. Histopathological examination revealed that no incidence of organ toxicity is attributed to the F50 diet. Overall, F50 group rats exhibited good growth and development with no adverse effects in biochemical, haematological, and histopathology parameters. Therefore, FWPH at the 50% level could be used as a potential dietary protein source in feed for better growth performance of the animal.

Sustainable valorization of meat processing wastewater with synergetic eutectic mixture based purification of R-Phycoerythrin from porphyrium cruentium

Wastewater effluent from meat processing industries are enriched with nutrients but remain underutilized. Therefore, an efficient method was administered by employing this resource for the cultivation of Porphyreum cruentium. The cultured biomass was exposed to a one-step disruption and selective purification method using a protic deep eutectic solvent to obtain a commercially significant pigment, R-Phycoerythrin (R-PE). Six protic deep eutectic solvents (pDES) were synthesized and their thermophysical activity determined. A synergy between microwave and cavitation (MACE-DLPME) has been achieved for the effective recovery of these membrane proteins. The addition of pDES provides the selective medium for the concentration of R-PE. Optimization of the MACE-DLPME method yields 95.9% (w/w) of R-PE. Preparative size exclusion chromatography resulted in (28 µg/g) of R-PE. Further ultra-purification by anion exchange chromatography enhances the purity fold of R-PE to 125. The resulting ultrapure fraction exhibits enhanced anti-platelet activity (1.56 mg/g ascorbic acid equivalent).

Integration of ozone with co-immobilized microalgae-activated sludge bacterial symbiosis for efficient on-site treatment of meat processing wastewater

Direct discharge of high concentration meat processing wastewater (MPW) into municipal sewage system will cause serious shock loading and reduce wastewater treatment efficiency, thus, efficient on-site pretreatment is usually required. Purpose of this study is to integrate ozone with microalgal biotreatment to achieve effective removal of both organic compounds and nutrients with one-step biodegradation and obtain high quality effluent dischargeable to municipal sewage system. Results showed that ozone pretreatment removed 35.0–90.2% color and inactivated 1.8–4.7 log CFU/mL bacteria in MPW. In post biotreatment using microalgae co-immobilized with activated sludge (ACS) bacteria, bacterial growth in ozone pretreated wastewater (7.1–8.1 log CFU/mL) were higher than non-pretreated control (6.0 log CFU/mL) due to enhanced biodegradability of wastewater pollutants. Algal biomass growth in wastewater pretreated with 0.5 (2489.3 mg/L) and 1 (2582.0 mg/L) minute's ozonation were improved and higher than control (2297.1 mg/L). Ozone pretreatment significantly improved nutrients removal. Following ozone pretreatment of 0.5 min, microalgal biotreatment removed 60.1% soluble chemical oxygen demand (sCOD), 79.5% total nitrogen (TN) and 91.9% total phosphate (PO43−) which were higher than control (34.4% sCOD, 63.4% TN, 77.6% total PO43−). Treated effluent contained 342.3 mg/L sCOD, 28.8 mg/L TN, 9.9 mg/L total PO43− and could be discharged into municipal sewage system. However, excessive ozone pretreatment displayed adverse impact on algal growth and sCOD removal. Therefore, integration of 0.5 min's ozone pretreatment with microalgae-based biotreatment is an efficient on-site treatment to simultaneously remove organic compounds and nutrients with one-step biodegradation.

Minimization of greenhouse gas emissions from extended aeration activated sludge process

AbstractOne of the greenhouse gas (GHG) emission resources is industrial wastewater treatment plants. In this study, on-site and off-site greenhouse gas emissions of an extended aeration activated sludge process in a meat processing wastewater treatment plant were estimated using a new developed approach based on the IPCC method. On-site emissions were regarded as the emissions related to the biochemical treatment process and microbial activity in the wastewater. On-site emissions were estimated from organic materials removal from wastewater and microbial mass activity. Biological oxygen demand (BOD) and chemical oxygen demand (COD) removal were considered as pollutant resources of carbon dioxide (CO2) and methane (CH4), respectively. Off-site emission was estimated from electricity consumption, chemical use and the sludge stabilization process. This paper aimed to determine and reduce on-site and off-site emissions for the extended aeration process in an industrial wastewater treatment plant. Modification of operating conditions was applied to reduce GHG emissions. The results revealed that electricity consumption was the major source of the greenhouse gas emissions for this process with a value of 6,002.77 kg CO2e/d. The minimization of total GHG emissions reached up to 17.1% by modifying the treatment process conditions.

Effect of Aeration Mode on Microbial Structure and Efficiency of Treatment of TSS-Rich Wastewater from Meat Processing

The present study investigated the effect of aeration mode on microbial structure and efficiency of treatment of wastewater with a high concentration of suspended solids (TSS) from meat processing in sequencing batch reactors (R). R1 was constantly aerated, while in R2 intermittent aeration was applied. DNA was isolated from biomass and analyzed using next-generation sequencing (NGS) and real-time PCR. As a result, in R1 aerobic granular sludge was cultivated (SVI30 = 44 mL g−1 MLSS), while in R2 a very well-settling mixture of aerobic granules and activated sludge was obtained (SVI30 = 65 mL g−1 MLSS). Intermittent aeration significantly increased denitrification and phosphorus removal efficiencies (68% vs. 43%, 73% vs. 65%, respectively) but resulted in decomposition of extracellular polymeric substances and worse-settling properties of biomass. In both reactors, microbial structure significantly changed in time; an increase in relative abundances of Arenimonas sp., Rhodobacterace, Thauera sp., and Dokdonella sp. characterized the biomass of stable treatment of meat-processing wastewater. Constant aeration in R1 cycle favored growth of glycogen-accumulating Amaricoccus tamworthensis (10.9%) and resulted in 2.4 times and 1.4 times greater number of ammonia-oxidizing bacteria and full-denitrifiers genes in biomass, respectively, compared to the R2.