Chemical Oxygen Demand Loading Research Articles

Deciphering the therapeutic, larvicidal, and chemical pollutant degrading properties of leaves-mediated silver nanoparticles obtained from Alpinia purpurata

The aim of the study was to synthesize silver nanoparticles (AgNPs) from Alpinia purpurata leaves and evaluate their cytotoxic, antimicrobial, antibiofilm, dye degradation, and larvicidal potentials. The synthesized AgNPs were characterized using ultraviolet-visible spectroscopy, Fourier transform infrared, and high-resolution transmission electron microscopy, which confirmed AgNPs synthesis and revealed nanoparticle size (10 to 30 nm) and the presence of silver. Cytotoxicity tests showed IC50 values of 4.59 ± 0.6 µg/mL in A549 cells and 3.48 ± 0.4 µg/mL in PA1 cells, inducing apoptosis and DNA fragmentation. Flow cytometry revealed cell cycle arrest at G0-G1 phase. AgNPs exhibited significant antimicrobial activity, with maximum inhibition zones against K. pneumoniae (23 ± 2 mm) and F. oxysporum (17 ± 2 mm), and minimum inhibitory concentration (MIC) values ranging from 12.5 ± 0.25 to 75 ± 2.5 µg/mL. They also reduced bacterial and fungal biomass and showed antibiofilm effects. Photocatalytic activity degraded methylene blue dye by 88.4 ± 1.4% in 60 minutes. Larvicidal activity resulted in 100% mortality of A. aegypti larvae after 48 hours exposure to AgNPs (10 mg/L), additionally reducing chemical oxygen demand (55.1 ± 2.1% to 63.8 ± 1.5%) and microbial load in wastewater (2.5 to 10 ppm).

Nitrate increases the capacity of an aerobic moving-bed biofilm reactor (MBBR) for winery wastewater treatment.

We used bench-scale tests and mathematical modeling to explore chemical oxygen demand (COD) removal rates in a moving-bed biofilm reactor (MBBR) for winery wastewater treatment, using either urea or nitrate as a nitrogen source. With urea addition, the COD removal fluxes ranged from 34 to 45 gCOD/m2-d. However, when nitrate was added, fluxes increased up to 65 gCOD/m2-d, twice the amount reported for aerobic biofilms for winery wastewater treatment. A one-dimensional biofilm model, calibrated with data from respirometric tests, accurately captured the experimental results. Both experimental and modelling results suggest that nitrate significantly increased MBBR capacity by stimulating COD oxidation in the deeper, oxygen-limited regions of the biofilm. Our research suggests that the addition of nitrate, or other energetic and broadly used electron acceptors, may provide a cost-effective means of covering peak COD loads in biofilm processes for winery or another industrial wastewater treatment.

TEXTILE EFFLUENT TREATMENT METHODS AND LIMITATIONS: A SUSTAINABLE AND ECOLOGICAL ASPECT

Industrial wastewater causes water and soil pollution, leading to life-threatening issues. Wastewater comprises several dyes, detergents, phenols, chemical salts, and heavy metals which enhance temperature, pH, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) load, total suspended solids, Total Dissolved Solids (TDS), chlorides, sulfate, and nitrate of affected sites. Dye effluent is highly toxic and leads to mutagenic and carcinogenic outcomes on living beings. Environmental laws are being passed more frequently to control mostly azo-based dyes in the environment. The effluent must be treated before being discarded directly into the ecological ecosystem so that it can be reutilised and recycled for domestic purposes. In the present scenario, using a physicochemical-based approach is inefficient for eliminating contaminants as the process is expensive, and a secondary pollutant, sludge, is produced after the treatment. Being cheap and eco-friendly, the therapy of dye-laden water using microorganisms is a trend. The authors of the current review study have tried to bridge the gap in the bioremediation of dye wastewater. The review imparts an overview of the textile industry, the generation of wastewater by it, the environmental pollution caused, and its impact on the ecosystem. The discussion mainly focuses on the detailed analysis of the last few decades on the decolorisation efficiencies of numerous bioremediation techniques involved in treating textile dye effluent. Additionally, the authors have tried to include the most recent developments in this area. By using eco-friendly methods, this study will undoubtedly help dyestuff companies and researchers.

Design and development of a pilot plant for the treatment of pharmaceutical wastewater containing molasses

Abstract The present work deals with the anaerobic treatment of molasses-bearing pharmaceutical wastewater using a specifically designed downflow anaerobic bioreactor (DFAB). The capacity of the designed DFAB was 1,000 L of adequate volume with necessary operational controls. Two types of anaerobic treatment, i.e. mesophilic and thermophilic treatments, were applied to the anaerobic biotransformation of wastewater under investigation. The efficiency of both treatments was compared in terms of reducing biochemical oxygen demand (BOD) and chemical oxygen demand (COD) load, as well as methane production. The anaerobic digestion process was carried out with the help of bacterial strains. The bacterial strains used in the mesophilic operation were acclimatised and utilised for the thermophilic treatment, which is a cost-effective and sustainable approach. A significant reduction in BOD and COD content of the wastewater was noticed after 10 days of retention time. Nearly 72–83% and 80–90% reduction in BOD values were recorded under mesophilic and thermophilic operations, respectively. Approximately 73–86% and 82–93% of COD content were reduced by mesophilic and thermophilic treatment, correspondingly. Methane production of 67 and 74% was achieved under mesophilic and thermophilic treatment, respectively. The designed DFAB showed remarkable treatment efficiency for wastewater and methane production.

Pollution load assessment in the form of TSS and COD emitted from an urbanized catchment in the aspect of administrative pollutant discharge fees on the example of the activity of the J1 CSO in Lodz (Poland)

The article presents the possibility of reducing fees for wastewater discharge from combined sewer overflows (CSOs) into the aquatic environment by minimizing the load emission of total suspended solids (TSS) and chemical oxygen demand (COD). The analysis was conducted based on limiting the wastewater volume discharged to the receiving water by one of the viable options, i.e., raising the overflow crest. The assessment was made on the example of the functioning J1 CSO in Lodz (in Polish: Łódź) in the years 2013–2015. An analysis of rainfall recorded in the J1 catchment area was also performed for this period. For the determination of the TSS and COD load emitted to the receiver, a predictive model based on rainfall parameters and the volume of discharged wastewater was used. To determine the wastewater volume emitted during individual activations of the J1 overflow, the model of the sewer network serving this catchment was calibrated in the EPA SWMM software. Simulations were conducted, considering different heights of the weir crest (static change). The results of the analyzes showed that raising the crest by 5 cm reduced the total fee for the J1 activity by 35% compared to its existing height in 2013 and about 40% for 2015. Raising the crest by 10 cm in 2015 enabled, for example, the J1 overflow activity to be in accordance with the applicable law. Reducing the amount of wastewater discharged to the receiver by using the overflow crest height adjustment method presented in the article may bring measurable financial and ecological benefits.

Is constructed wetlands carbon source or carbon sink? Case analysis based on life cycle carbon emission accounting

Constructed wetlands (CWs) are widely used to polish the effluent of wastewater treatment plants and micro-polluted river or lake water. However, the impact of large-scale applications of CWs on carbon emissions is unclear. In this study, the carbon footprints of two full-scale hybrid CWs were determined based on life cycle assessment (LCA). Results showed that the carbon emission of CW ranged from 0.10 to 0.14 kg CO2-eq/m3, and was significantly correlated with the influent chemical oxygen demand loads and electricity consumption. However, CW would approach carbon neutrality during the service period when taking plant carbon sequestration into consideration. Compared with other advanced wastewater treatment technologies, CWs showed significant low-carbon emission and cost-effective benefits. This study clarified the role of CWs in the carbon cycle and would provide guidance for the construction and management of CWs.

Comparative evaluation of low-cost ceramic membrane and polymeric micro membrane in algal membrane photobioreactor for wastewater treatment

Algal-bacterial membrane photobioreactor (AMPBR) is proven as a highly energy-efficient process for treating domestic wastewater. This study compared the application of polymeric micro-membrane (PMM) and a low-cost ceramic membrane (LCM) to the AMPBR process for treating domestic wastewater with low and high organic pollution levels. Experiments were conducted over 57 days using two PMM-AMPBRs and two LCM-AMPBRs, operating on a 12-h dark/light cycle in a continuous mode. Simulated wastewater containing varying levels of chemical oxygen demand (COD) was fed to reactors for a consistent hydraulic residence time (HRT) of 7 d and a flux rate of 100 L/m2/d. PMM and LCM-AMPBRs demonstrated efficient wastewater treatment capabilities, achieving COD removal rates exceeding 94% and 95% for high and low COD loadings, respectively. PMM-AMPBR achieved 54.1% TN removal at low COD loading, while LCM-AMPBR achieved 57.2%. These removal efficiencies decreased to 45.6% and 47.0% under high COD loading. Total Phosphorus (TP) removal reached 29–33% for PMM-AMPBRs and 21–24% for LCM-AMPBRs, irrespective of COD loading. LCM-AMPBRs showed significantly lower fouling frequency than PMM-AMPBRs. The biomass production rate decreased with increasing COD loading and achieved 40 mg/L/d at low COD loading for both AMPBRs. Net energy return (NER) values for both AMPBRs were close to 0.87, indicating them as energy-efficient processes. Considering the cost-effectiveness and comparable performance, LCM-AMPBR could be a viable alternative to PMM-AMPBR for wastewater treatment, particularly under low COD loading conditions.

Reduction of pollution loads based on sewage treatment projects around a lake: A case study on Erhai Lake.

Erhai Lake is a highland freshwater lake in Dali, China. Rapid tourism development has generated large amounts of pollutants. Since 2015, six wastewater treatment plants (WWTPs) have been built to treat wastewater collected through sewage interception projects. In this study, reductions in the pollution load of wastewater from different sources were evaluated by considering the effects of groundwater leakage, microbial degradation, and rainfall-runoff. The results showed that the systems reduced the chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) loads by 85, 83, and 85%, respectively. Discharge wastewater has the characteristics of a low concentration of domestic sewage discharge, large tourist sewage discharge, and high concentration of livestock wastewater. Due to the high groundwater level, there is groundwater infiltration in the influent water of WWTPs, which dilutes the pollutant concentration of the influent and, therefore, results in a lower treatment efficiency. Further treatment of tailwater also reduced the pollution loads discharged into the lake as well as the COD and TN by 10.25 and 22.90%, respectively. The results indicate that groundwater infiltration in the sewer network system is the primary target to be addressed in future developments.

Amalgamated silica-glutaraldehyde based cost effective leather tanning agent and its sustainable benefits: A metal free collagen stabilisation

Presently, there is a need for development of cleaner and sustainable tanning system by introducing biocompatibility and degradability to the leather without affecting its physical properties. Particularly, tanners seek chrome-free tanning systems due to their cleaner image, market demand, and good physical properties. Amongst tanning agents, silica and its combination have been identified as a greener tanning system. In the present study, a combination tanning system based on surface modified silica and aldehyde has been developed. The main invention lies in identifying a new tanning system based on silica with an amine terminal followed by dialdehyde post treatment with an appropriate post-tanning process. Initially, the silica will stabilize the collagen fibres through multiple hydrogen bonding and electrostatic interactions. Later, adding aldehyde enhances the bonding between silica and collagen through multiple intermolecular crosslinking. This was further validated by the molecular interaction studies of collagen with a silica-glutaraldehyde combination system. This developed chrome-free tanning process produces leathers exhibiting reasonable thermal stability of around 90 °C with reduced chemical oxygen demand (COD) load and no chromium in the wastewater. Due to the synergistic effect of silica and aldehyde, even the tanned leather exhibited improved antimicrobial activity against gram-positive Bacillus subtilis and gram-negative Escherichia coli. One of the main benefits of this new tanning system is the lower environmental impact with an E-factor of 0.23. Sustainability indicators suggest that the tanning by silica combination found to be environmentally friendly and cost effective method as compared to conventional chrome tanning process.

Biochar-based geopolymer nanocomposite for COD and phenol removal from agro-industrial biorefinery wastewater: Kinetic modelling, microbial community, and optimization by response surface methodology

Agro-industrial biorefinery effluent (AIBW) is considered a highly polluting source responsible for environmental contamination. It contains high loads of chemical oxygen demand (COD), and phenol, with several other organic and inorganic constituents. Thus, an economic treatment approach is required for the sustainable discharge of the effluent. The long-term process performance, contaminant removal and microbial response of AIBW to rice straw-based biochar (RSB) and biochar-based geopolymer nanocomposite (BGC) as biosorbents in an activated sludge process were investigated. The adsorbents operated in an extended aeration system with a varied hydraulic retention time of between 0.5 and 1.5 d and an AIBW concentration of 40–100% for COD and phenol removal under standard conditions. Response surface methodology was utilised to optimize the process variables of the bioreactor system. Process results indicated a significant reduction of COD (79.51%, 98.01%) and phenol (61.94%, 74.44%) for BEAS and GEAS bioreactors respectively, at 1 d HRT and AIBW of 70%. Kinetic model analysis indicated that the Stover-Kincannon model best describes the system functionality, while the Grau model was better in predicting substrate removal rate and both with a precision of between R2 (0.9008–0.9988). Microbial communities examined indicated the abundance of genera, following the biosorbent addition, while RSB and BGC had no negative effect on the bioreactor's performance and bacterial community structure of biomass. Proteobacteria and Bacteroidetes were abundant in BEAS. While the GEAS achieved higher COD and phenol removal due to high Nitrosomonas, Nitrospira, Comamonas, Methanomethylovorans and Acinetobacter abundance in the activated sludge. Thus, this study demonstrated that the combination of biosorption and activated sludge processes could be promising, highly efficient, and most economical for AIBW treatment, without jeopardising the elimination of pollutants or the development of microbial communities.

Comparative analysis in the performances of four in‐ground lagoon anaerobic digesters treating palm oil mill effluent (POME)

AbstractWhile palm oil mill effluent (POME) from different sources will have varying characteristics due to the different process flows in mills, efficient monitoring and performance evaluation of anaerobic digesters in POME treatment are crucial to ensure stable biogas production with minimal operational problems. Therefore, this study aims to evaluate and compare the performances of in‐ground lagoon anaerobic digesters under mesophilic conditions in four different biogas plants (BGPs A, B, C and D) located in Malaysia with respect to total chemical oxygen demand (COD) removal and total biogas produced. Results show that all BGPs are still functioning well with satisfactory methane yields (.135–.364 Nm3 CH4/kgCOD removed) and COD removal efficiencies (67%–85%). ANOVA analysis shows that organic loading rate (OLR), temperature (T) and recirculation ratio (RR) have significant effects on the COD removal and biogas production of all four plants. BGP B has the highest amount of biogas produced (4.12 × 105 Nm3/month) and COD removal rate amongst other BGPs due to its most stable and lowest T (<40°C), high RR, and consistent and high COD load. Conversely, BGP D has the lowest COD removal and biogas production, which are mainly contributed by a high COD inlet (92 000 mg/L) and a high T in the anaerobic digester (48.7°C). Despite having a similar design of an anaerobic digester, this comparative study reveals that different BGPs will have different optimum operating conditions and limitations, depending not only on the operating conditions of the BGP (OLR, T and RR) but also on the raw POME quality stemming from the palm oil milling process. A future study would be focused on the optimisation of four BGPs for maximum biogas removal.

Spatiotemporal domestic wastewater variability: Assessing implications of population mobility in pollutants dynamics

Abstract. Population mobility can change pollutants variability in domestic wastewater (DW). However, the implications of mobility on DW variability in small localities are rarely analyzed and visualized in space and time. Often, only limited mobility data is available for these types of areas. In this study, we investigate the implications of population mobility on DW variability using an Agent-Based model (ABM). The ABM simulates the spatiotemporal DW variability of chemical oxygen demand (COD) across the sewage network. Two scenarios are tested, one where inhabitants commute daily to school and work and the other when the population remains at home. In each scenario, the spatial variability of COD loads is mapped and analyzed at the sewage maintenance holes. Apparent changes are observed between these spatial patterns. The obtained maps show that DW loads vary across space, where substantial COD load differences exist between the two mobility scenarios. Population mobility implicates higher COD loads at some maintenance holes compared to a scenario with inhabitants remaining home. The spatial DW variability also gets higher upstream and lower downstream, implicating that mobility does not substantially generates variability at the wastewater treatment plant inflow. The preliminary results suggest that population mobility impacts the spatial DW variability across the sewage network, which requires further analysis with wider temporal coverage.

High biogas evolution of distillery wastewater under potassium toxicity in a three-stage upflow anaerobic sludge blanket

This investigation aimed to enhance the methanogenic activity of distillery wastewater containing high potassium (K) content in a mesophilic three-stage upflow anaerobic sludge blanket (UASB). The three-stage UASB could not function at a chemical oxygen demand (COD) loading rate greater than 3 kg/m3d due to the K toxicity, causing system failure. The K concentration in the distillery wastewater was 9000–10,000 mg/L, close to the severe inhibitory range for anaerobes (> 12,000 mg/L). Hence, the wastewater was diluted to reach moderate K toxicity. Surprisingly, the three-stage UASB could function effectively, providing high optimum and maximum COD loading rates (20 and 40 kg/m3d, respectively). This was because the three-stage UASB was regulated under a slow stepwise increase in the COD loading rate to achieve fully adapted anaerobe communities for each COD loading rate. This then led to the high ability to withstand the moderate inhibition of K via the successive development of sludge granules.

Utilization of vegetable tannins for stabilization of collagen fibers by using supported process enzyme

Tanning is the process of treating animal skins or hides to produce leather, which is more durable and less susceptible to decomposition. The leather industry has been pushed to develop tanning systems that utilize natural products due to environmental concerns. Vegetable tanning is one of the oldest methods, but its usage is limited due to the high organic load in the effluent generated. This load is difficult to degrade and results in high biological and chemical oxygen demand. This study aimed to develop an eco-friendly tanning process for protein fibers using proteolytic enzymes. The goal was to improve the exhaustion of vegetable tannins by increasing their uptake during the tanning process. The optimized experimental process, which involved enzymatic treatment of protein fibers, resulted in an exhaustion of 97% compared to 83% in conventional vegetable tanning processes. Enzyme treatment before tanning also led to a slight improvement in hydrothermal stability, as well as slightly better physical properties of the resulting leathers compared to conventionally tanned leathers. The enzymatic process has the added benefit of reducing total solids (TS) and chemical oxygen demand (COD) loads in the identified streams by 80% and 33%, respectively.

Greenhouse gas reduction of co-benefit-type wastewater treatment system for fish-processing industry: A real-scale case study in Indonesia

This study examined the application of co-benefit-type wastewater treatment technology in the fish-processing industry. Given that there was a dearth of information on fish-processing industrial wastewater in Indonesia, site surveys were conducted. For the entire fish-processing industry throughout the country, the dissemination rate of wastewater treatment facilities was less than 50%. Using a co-benefit approach, a real-scale swim-bed technology (SBT) and a system combining an anaerobic baffled reactor (ABR) with SBT (ABR–SBT) were installed in a fishmeal processing factory in Bali, Indonesia, and the wastewater system process performance was evaluated. In a business-as-usual scenario, the estimated chemical oxygen demand load and greenhouse gas (GHG) emissions from wastewater from the Indonesian fish-processing industry were 33 000 tons per year and 220 000 tons of equivalent CO2 per year, respectively. On the other hand, the GHG emissions in the co-benefit scenarios of the SBT system and ABR–SBT system were 98 149 and 26 720 tons per year, respectively. Therefore, introducing co-benefit-type wastewater treatment to Indonesia’s fish-processing industry would significantly reduce pollution loads and GHG emissions.

Electrochemical Insight into the Use of Microbial Fuel Cells for Bioelectricity Generation and Wastewater Treatment

Microbial fuel cell (MFC) technology is anticipated to be a practical alternative to the activated sludge technique for treating domestic and industrial effluents. The relevant literature mainly focuses on developing the systems and materials for maximum power output, whereas understanding the fundamental electrochemical characteristics is inadequate. This experimental study uses a double-chamber MFC having graphite electrodes and an anion-exchange membrane to investigate the electrochemical process limitations and the potential of bioelectricity generation and dairy effluent treatment. The results revealed an 81% reduction in the chemical oxygen demand (COD) in 10 days of cell operation, with an initial COD loading of 4520 mg/L. The third day recorded the highest open circuit voltage of 396 mV, and the maximum power density of 36.39 mW/m2 was achieved at a current density of 0.30 A/m2. The electrochemical impedance spectroscopy analysis disclosed that the activation polarization of the aerated cathode was the primary factor causing the cell’s resistance, followed by the ohmic and anodic activation overpotentials.

Robustness and stability of acetate-driven partial denitrification (PD) in response to high COD/NO3−-N

Partial Denitrification (PD) producing nitrite for anammox may face the issue of relatively high chemical oxygen demand (COD) loading (i.e., COD/NO3−-N) due to real wastewater being changed in substrate concentration and flowrate. In this study, three PD systems (R1, R2, R3) with sodium acetate providing electrons were developed to investigate the influence of the relatively high COD/NO3−-N ratios (4.0, 6.0, and 8.0) on NO2−-N production and the subsequent recoverability. It was found that a relatively high NO2−-N production with nitrate-to-nitrite transformation ratio (NTR) of 74.0% could be still obtained despite COD/NO3−-N even improving to 8.0 under limited reaction time (10 min) with small nitrate remaining. However, a deteriorated nitrite production was observed with sufficient reaction time (15 min) with NTR being lowered to 19.2%. Delightedly, when reducing influent COD/NO3−-N to a normal level of 3.0, PD with high nitrite production was rapidly achieved after suffering from a relatively high COD/NO3−-N (4.0–8.0) for 130 cycles. Besides, it was found the relatively high COD/NO3−-N had a minor influence on the recoverability of PD, as evidenced by the close NTRs. Microbial analysis revealed the relative abundance of PD functional bacteria, Thauera, decreased under high COD/NO3−-N, while it is still highly dominated in the systems, varying from 75.1% in R1 to 62.8% in R3 after around 110-cycles recovery. Furthermore, it appeared that the high pH (9.1–9.2) induced by sodium acetate also likely played a role in maintaining the excellent PD. Overall, this study demonstrated the robustness and stability of acetate-driven PD in response to high COD/NO3−-N, further informing the technological superiority of PD in supplying stable and efficient nitrite, which provided solid technical support to apply it with anammox for high-efficient N removal.

BaTiO3 Functional Perovskite as Photocathode in Microbial Fuel Cells for Energy Production and Wastewater Treatment.

Microbial fuel cells (MFCs) provide new opportunities for the sustainable production of energy, converting organic matter into electricity through microorganisms. Moreover, MFCs play an important role in remediation of environmental pollutants from wastewater with power generation. This work focuses on the evaluation of ferroelectric perovskite materials as a new class of non-precious photocatalysts for MFC cathode construction. Nanoparticles of BaTiO3 (BT) were prepared and tested in a microbial fuel cell (MFC) as photocathode catalytic components. The catalyst phases were synthesized, identified and characterized by XRD, SEM, UV-Vis absorption spectroscopy, P-E hysteresis and dielectric measurements. The maximum absorption of BT nanoparticles was recorded at 285 nm and the energy gap (Eg) was estimated to be 3.77 eV. Photocatalytic performance of cathodes coated with BaTiO3 was measured in a dark environment and then in the presence of a UV-visible (UV-Vis) light source, using a mixture of dairy industry and domestic wastewater as a feedstock for the MFCs. The performance of the BT cathodic component is strongly dependent on the presence of UV-Vis irradiation. The BT-based cathode functioning under UV-visible light improves the maximum power densities and the open circuit voltage (OCV) of the MFC system. The values increased from 64 mW m-2 to 498 mW m-2 and from 280 mV to 387 mV, respectively, showing that the presence of light effectively improved the photocatalytic activity of this ceramic. Furthermore, the MFCs operating under optimal conditions were able to reduce the chemical oxygen demand load in wastewater by 90% (initial COD = 2500 mg L-1).

Role of biochar in anaerobic microbiome enrichment and methane production enhancement during olive mill wastewater biomethanization.

The current research work attempted to investigate, for the first time, the impact of biochar addition, on anaerobic digestion of olive mill wastewater with different initial chemical oxygen demand loads in batch cultures (10g/L, 15g/L, and 20g/L). Methane yields were compared by applying one-way analysis of variance (ANOVA) followed by post-hoc Tukey's analysis. The results demonstrated that adding at 5g/L biochar to olive mill wastewater with an initial chemical oxygen demand load of 20g/L increased methane yield by 97.8% and mitigated volatile fatty acid accumulation compared to the control batch. According to the results of microbial community succession revealed by the Illumina amplicon sequencing, biochar supplementation significantly increased diversity of the microbial community and improved the abundance of potential genera involved in direct interspecies electron transfer, including Methanothrix and Methanosarcina. Consequently, biochar can be a promising alternative in terms of the recovery of metabolic activity during anaerobic digestion of olive mill wastewater at a large scale.

Improving water-use efficiency and environmental performances in an integrated woven-knitted fabric printing-dyeing textile mill

In this study, it was aimed to improve water-use efficiency and improve environmental performance with techno-economic water-use efficiency practices in an integrated textile mill that produces woven and knitted fabrics. In this context, detailed on-site investigations and data collection studies were carried out in the mill. All water consumption and wastewater generation points were determined. Specific water consumptions and specific wastewater amounts were calculated basis on the basic production processes, auxiliary processes, and non-process areas. Samples were collected from raw water, process water, process wastewaters, and composite wastewater at different periods and analyzed. Thus, reuse potentials of the process wastewaters were evaluated. Specific pollutant loads of process and composite wastewaters were also calculated. Moreover, saving/reduction potentials were calculated by comparing the specific water consumption, wastewater amounts, and pollutant loads of the mill with similar textile mills. It was decided to implement a total of 13 water-use efficiency practices to increase the water-use efficiency and environmental performance of the mill. Ultimately, it was found that reduction of 13.8–25.6% in the total water consumption, 18.2–32.9% in the total wastewater amount and 15.9–35.7% in the total chemical oxygen demand (COD) loads of the mill could be achieved after the implementation of suggested practices. The estimated payback periods were found to be between 2 and 45 months. This study shows that with low-cost water-use efficiency practices, significant reductions in water consumption, wastewater amounts, and pollution loads of wastewater can be achieved in similar textile mills. This study can be inspiring for other textile mills to improve their water-use efficiency performances. Also, it can provide significant contributions to industry stakeholders, policy makers and researchers in terms of presented water-use efficiency practices, obtained water-wastewater reductions/savings and applied methodology.