Terms Of Chemical Oxygen Demand Research Articles

The Investigation of Treatment of Pistachio Processing Industrial Wastewater by Electrochemical Methods in Terms of Chemical Oxygen Demand and Total Phenol Removal

<p>This work aims to investigate the efficiency of electrocoagulation (EC) of pistachio processing industrial wastewater (PPIW) using the continuous EC process. The tubular reactor made of stainless steel with an internal diameter of 60 mm was used as a cathode electrode. The effect of some parameters was examined on the removal of chemical oxygen demand (COD) and total phenols (TP) removal efficiency. The influences of the initial pH of wastewater (from 4 to 8), flow rate (from 25 to 125 mL/min), current density (from 7 to 21 mA/cm<sup>2</sup>), and supporting electrolyte type (NaCl, NaNO<sub>3</sub>, and Na<sub>2</sub>SO<sub>4</sub>), supporting electrolyte concentration (from 10 to 100 mg/L NaCl) on removal efficiency were investigated to determine the best experimental conditions. The examination of the physico-chemical parameters during the EC treatment showed that the best removal efficiency was obtained under conditions where the flow rate was 25 mL/min (20 min reaction time), the pH value was 5.2, and the current density was 21 mA/cm<sup>2</sup> has set. Under these experimental conditions, COD and TP removal efficiency were found to be 75% and 97%, respectively, while energy consumption was 18.5 kW h/m<sup>3</sup>. The study results show that the EC can be applied to PPIW pre-treatment.</p>

Smart win–win waste management: superhydrophobic filter using valorized cellulose acetate from discarded cigarette butts for cleaning up marine oil spill at Hurghada Red Sea shore in Egypt

The essential target of academics and the industrial sector is the innovation of an industrial ecology approach. Worldwide, cigarette butts (CBs) comprise the most predominant form of litter that spreads into the ecosystem and inland. In the meantime, oil is spilled into marine life from various activities and transportation. The result is a complex oil–water composition in a high concentration that causes severe hazards to the environment and to aquatic life. In this regard, the current investigation focuses on obtaining hydrophobic cellulose acetate from CBs for use as a filter media. The filter is applied in marine oil spill separation as a win–win industrial ecology technique. Initially, the separated CB residuals were prepared by successive washing. Subsequently, the obtained cellulose acetate fibers were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Furthermore, the new CB-based filters were used in the separation/adsorption of marine oil wastewater spill. Subsequently, a group of experiments were conducted. The results showed that the cleanup efficiency could be up to 99% in terms of chemical oxygen demand (COD). Moreover, the products were recovered by washing with hot water for further use, which showed high removal activity that reached 95% after successive uses. In comparison to commercial oil sorption materials, the results were promising as the RP-C18 cartridge revealed a maximum oil removal of 90%. Such preliminary data on a cellulose acetate filter scheme are a good indicator in the development of an oil spill facility, being a suitable candidate for controlling oil wastewater effluent streams.

Cheese wastewater treatment through combined coagulation-flocculation and photo-Fenton-like advanced oxidation processes for reuse in irrigation: effect of operational parameters and phytotoxicity assessment.

The present study aims to investigate the efficiency of a combined cheese wastewater treatment approach involving coagulation with ferric chloride coupled with a photo-Fenton-like oxidation process for potential reuse in irrigation. Laboratory-scale tests were conducted, examining the effect of various operational parameters on the treatment process. Specifically, the effects of initial wastewater pH, coagulant dosage, decantation time for the coagulation process, and initial pH, chemical oxygen demand (COD) concentration, and Fe3+ and H2O2 dosages for photo-Fenton-like oxidation were studied. Coagulation was found effective at natural pH of 6 and showed a highest removal efficiency in terms of COD (50.6%), biological oxygen demand BOD5 (42.1%), turbidity (99.3%), and least sludge volume generation (11.8% v/v) for an optimum coagulant dose of 400mg Fe3+ L-1 and 8h of decantation time. Thereafter, photo-Fenton-like oxidation (Fe3+/H2O2/UVA-300W) of the pretreated cheese effluent enhanced the removal of COD, BOD5 and TOC to 91.2%, 91.4%, and 97.5%, respectively, using the optimized conditions (pH = 3; [Fe3+] = 5.0 × 10-4mol L-1; [H2O2] = 0.2mol L-1 and tirr = 24h). This study also shows that the proposed combined process allowed a significant phytotoxicity reduction toward lentil seed germination. The obtained outcome was encouraging and supports the possible use of the treated cheese wastewater as an additional water source for agricultural irrigation.

Enhancing pharmaceutical wastewater treatment: Ozone-assisted electrooxidation and precision optimization via response surface methodology

Amid the critical global demand for effective wastewater treatment, our study presents a pioneering approach to address pharmaceutical wastewater treatment. We exploited the potential of electrooxidation (EO) and introduced an innovative process with ozone-assisted electrooxidation (EO/O3), using Pt-coated Ti electrodes (Pt/Ti). The core aim is to tackle the removal of organic pollutants in terms of chemical oxygen demand (COD), color, and the UV absorption peak at 300 nm (UV300). This endeavor took place in a carefully controlled batch-mode reactor. Rigorous experimental design and optimization methodology was conducted using the cutting-edge statistical tool known as the Box-Behnken Design (BBD). Using current density, initial pH, and electrolysis time as independent variables in our statistical models resulted in remarkable outcomes. Under optimized conditions (110.63 A m−2 current density and pH 4.5 in 477 min), our stand-alone electrooxidation effectively reduced COD by 70.5 %, color by 81.25 %, and decreased UV300 by 40.01 %. However, when ozone joined the stage to assist the electrooxidation, the performance raised to new heights. It achieved an impressive 84 % reduction in COD, a remarkable 99.43 % color decrease, and a significant 49.63 % drop in UV300 under optimized conditions (150 A m−2 current density and pH 8.79 in 480 min). In addition, this study was further distinguished by the positive results obtained in the kinetic analysis. The findings showcase ozone-assisted electrooxidation as a highly effective approach for pharmaceutical wastewater treatment, emphasizing the novelty and significance of this study.

Microalgae and co-culture for polishing pollutants of anaerobically treated agro-processing industry wastewater: the case of slaughterhouse

Anaerobically treated slaughterhouse effluent is rich in nutrients, organic matter, and cause eutrophication if discharged to the environment without proper further treatment. Moreover, phosphorus and nitrogen in agro-processing industry wastewaters are mainly removed in the tertiary treatment phase. The objective of this study is to evaluate the pollutant removal efficiency of Chlorella and Scenedesmus species as well as their co-culture treating two-phase anaerobic digester effluent through microalgae biomass production. The dimensions of the rectangular photobioreactor used to conduct the experiment are 15 cm in height, 20 cm in width, and 30 cm in length. Removal efficiencies between 86.74–93.11%, 96.74–97.47%, 91.49–92.91%, 97.94–99.46%, 89.22–94.28%, and 91.08–95.31% were attained for chemical oxygen demand, total nitrogen, nitrate, ammonium, total phosphorous, and orthophosphate by Chlorella species, Scenedesmus species, and their co-culture, respectively. The average biomass productivity and biomass yield of Chlorella species, Scenedesmus species, and their co-culture were 1.4 ± 0.1, 1.17 ± 0.12, 1.5 ± 0.13 g/L, and 0.18, 0.21, and 0.23 g/L*day, respectively. The final effluent quality in terms of chemical oxygen demand, total nitrogen, and total phosphorous attained by Chlorella species and the co-culture were below the permissible discharge limit for slaughterhouse effluent standards in the country (Ethiopia). The results of the study showed that the use of microalgae as well as their co-culture for polishing the nutrients and residual organic matter in the anaerobically treated agro-processing industry effluent offers a promising result for wastewater remediation and biomass production. In general, Chlorella and Scenedesmus species microalgae and their co-culture can be applied as an alternative for nutrient removal from anaerobically treated slaughterhouse wastewater as well as biomass production that can be used for bioenergy.Graphical

Influence of mixing conditions on coagulant recovery efficiency and quality

Abstract In this work, the influence of mixing conditions on aluminium recovery from alum sludge and on the recovered coagulant (RC) quality was investigated using acidic treatment. The response surface methodology with a Face Centred Design was used to evaluate the effects of velocity gradient and mixing time on aluminium recovery efficiency, and on the chemical oxygen demand (COD), total suspended solids (TSS) and total phosphorus contents of the RC. No significant effects of both mixing intensity and mixing time on aluminium recovery efficiency were observed; however, these factors significantly affected the quality of the RC in terms of COD, TSS and total phosphorus. The higher velocity gradient increased COD and TSS and the longer mixing time increased phosphorus and TSS in the RC. Operational conditions velocity gradient = 100 s−1 and mixing time = 5 minutes) for aluminium recovery were suggested on economic basis. At these conditions, the RC presented the lowest values of TSS and total phosphorus (100 mg L−1 and 7.0 mg P L−1, respectively), and the following other characteristics: 1,001 mg Al L−1; 384 mg Fe L−1; 1100 mg COD L−1.

Elevated purification of urban rainwater runoff using a calamus constructed wetland with multi-layer carrier fillers

Urban water body pollution caused by storm-water runoff is increasingly serious due to rising global urbanization. We evaluated the effectiveness of a calamus vertical flow constructed wetland purifying urban runoff. This wetland was constructed using three filler layers of rare earth porcelain sand, ceramsite, and clinoptilolite respectively. The results revealed that under the optimal hydraulic load of 80 L/(m2·h), pollutants removal efficiency with the study wetland reached 89.9 %, 95.0 %, 84.7 %, and 76.2 % for the moderate rain runoff, in terms of COD (chemical oxygen demand), SS (suspended solids), TN (total nitrogen) and TP (total phosphorus) respectively. The removal rates of COD, SS, TN and TP by plants and the soil layer together were up to 64.9 %, 50.0 %, 58.1 %, and 28.6 %, respectively, while the rare earth porcelain sand layer had the highest contribution to the removal rate of TP (42.8 %), and the filler removal effect for phosphorus was more significant than that of plants and the soil layer. Although the influent water quality fluctuates with runoff from moderate to heavy torrential rain intensities, most of the effluent water meets the discharging standards. While the effluent quality of light rain runoff with high pollution load slightly exceeded the standards, it still removal rate as high as 88 %, 96.3 %, 73.3 %, 76.2 % for COD, SS, TN, TP.

Preparation of Self-Releasing Carbon Biofilm Carrier Based on Corncob and Denitrification Properties

Wastewater with a low carbon/nitrogen (C/N) ratio is widespread and difficult to treat. The addition of an external carbon source is an effective method for treating such wastewater. Therefore, we aimed to prepare a self-releasing carbon biofilm carrier using agricultural waste (corncobs), polyvinyl alcohol, and sponge iron in various ratios to provide a carbon source that would facilitate denitrification, providing an optimal environment for microorganisms. We found that the carbon release of the MAC biofilm carrier that accumulated over 60 d was 116.139 mg of chemical oxygen demand (COD)·g−1, whereas the accumulated total nitrogen release was approximately 0 mg·(g·d)−1. The NO3−-N removal rate after 24 h reached 98.1%, whereas the theoretical use rate of the carbon source (in terms of COD) was stable at 90.34%. In addition, the sum of the abundances of the denitrifying and cellulose-degrading bacteria was 49.89%. Furthermore, biofilm carriers are used as functional carriers that contribute to cellulose degradation, a process in which sponge iron produces Fe2+ to provide electron donors and shuttles for denitrifying bacteria and forms the iron cycle, thereby inducing an increase in microbial abundance; this increase then facilitates the microbial degradation of cellulose and synergistic denitrification through interspecific bacterial cooperation. This study provides a new and effective method for enhancing the denitrification of wastewater with low C/N ratios.

Enhanced Onsite Treatment of Domestic Wastewater Using an Integrated Settler-Based Biofilm Reactor with Efficient Biogas Generation

The growing population and increasing urbanization have led to a surge in domestic wastewater generation, posing significant challenges for effective and sustainable treatment. The present study demonstrates a novel and sustainable approach for the onsite treatment of domestic wastewater using an integrated settler-based biofilm reactor (ISBR) with efficient biogas generation. The ISBR provides an optimized environment for the growth of biofilm, facilitating the removal of organic pollutants and pathogens. Moreover, the ISBR enables the recovery of a valuable resource in the form of biogas, thus enhancing the overall utility of the treatment process. The performance of the ISBR was comprehensively evaluated at laboratory scale through treating the actual domestic wastewater generated from the hostel of Manipal University Jaipur. The ISBR system was operated under an ambient environment at a hydraulic retention time (HRT) of 24 h. The results demonstrated remarkable efficiency in terms of chemical oxygen demand (COD), total suspended solids (TSS), and coliforms removal, with average removal efficiency being more than 90%. According to the COD mass balance analysis, 48.2% of the influent COD was recovered as bioenergy. The chromatogram revealed a high percentage of methane gas in the collected biogas sample. The field emission scanning electron microscope (FESEM) analysis of the accumulated sludge in the ISBR system depicted the morphology of methanogenic bacteria. Both the experimental and theoretical results confirmed the feasibility and sustainability of the ISBR system at the onsite level.

Comparison of aerobic and anoxic-oxic sequential batch reactors for treating textile wastewater

ABSTRACT The discharge of untreated textile dyeing wastewater containing azo dyes has significant ecological consequences. The incomplete biodegradation of these dyes can produce harmful and carcinogenic aromatic amines (AAs), which pose a threat to the environment. This study evaluates the treatment of real textile dyeing wastewater containing azo dyes by two different systems: an anoxic sequential batch reactor (A/O-SBR) and an aerobic sequential batch reactor (A-SBR). The effects of hydraulic retention time (HRT) on both systems were investigated in terms of chemical oxygen demand (COD), total nitrogen (TN), color, and AAs removal. Ranging between 85% and 92%, the COD removal efficiency was almost similar in the A/O-SBR and A-SBR systems, suggesting that the aerobic phase is primarily responsible for COD removal. However, A/O-SBR showed higher removal of color (90%) than A-SBR (75%) due to the presence of an anoxic phase. HRT has a significant impact on color removal in both systems. However, there was no significant effect on COD removal when HRT exceeded 12 h. According to LC-MS/MS analysis, increasing the HRT from 12 h to 24 h increased the AAs concentration in the anoxic phase, from 253 ng/L to 261 ng/L and slightly decreased the AAs concentration in the aerobic phase from 107 ng/L to 102 ng/L. This resulted in an overall improvement in both dye and AAs removal. The presence of aerobic phase in A/O-SBR and A-SBR demonstrates strong AAs removal capacity. GC-MS/MS analysis indicated that as the HRT of A/O-SBR and A-SBR increased, the number of by-products increased.

The Photocatalytic Activity of Green Zinc Oxide Nanoparticles in The Treatment of Aerobically Palm Oil Mill Effluent

Traditional treatment of aerobically palm oil mill effluent (A-POME) is incapable of removing the colour and organic load that does not exceed the discharge standard limit to the stream channel. Green synthesis nanoparticles (NPs) provide a significant potential for substantial performance in the photocatalytic degradation of high-strength wastewater. Therefore, the current project's goal is to investigate the photocatalytic degradation performance of A-POME in the addition of green Zinc Oxide Cymbopogon Citratus (ZnO–CC) NPs in terms of chemical oxygen demand (COD), turbidity, and colour removal. The outcomes showed that pH 8 and a ZnO-CC NPs loading of 0.3g/L was ideal for the photocatalytic degradation of A-POME with a significant percentage reduction of turbidity (68.03%), colour (48.11%), and COD (75.4%). The equilibrium data revealed a better fit Langmuir-Hinshelwood models with higher R2 and K values of 0.9906 and 0.0225, respectively. Increased ZnO–CC NPs loading in alkaline medium aided in the breakdown of A-POME pollutants by increasing the surface area accessible for UV light adsorption during the photocatalytic process. Thus, the finding from this study can assist the palm oil mill sector in improving A-POME treatment to provide high-quality treated effluent.

Low-cost treatment method for organic matter and nutrients in landfill leachate.

In this study, the ability of low-cost composite adsorbents to treat organic compounds in terms of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) was investigated. The composite adsorbents were composed of washed sea sand (WSS), dewatered alum sludge (DAS), zero-valent iron (ZVI), and granular activated carbon (GAC). The removal efficiency of COD in landfill leachate by a composite adsorbent (composed of WSS (40%), DAS (40%), ZVI (10%), and GAC (10%) in weight) was 79.93 ± 1.95%. The corresponding adsorption capacity was 8.5 mg/g. During batch sorption experiments, the maximum COD removal efficiencies given by DAS, WSS, ZVI, and GAC were 16, 51.3, 42, and 100.0%, respectively. The maximum removal efficiencies of the above composite adsorbent for TN and TP were 84.9 and 97.4%, respectively, and the adsorption capacities were 1.85 and 0.55 mg/g, respectively. The Elovich isotherm model gave the best fit for COD, TN, and TP adsorption. This composite adsorbent can treat more than one contaminant simultaneously. The application of DAS and ZVI to make an efficient adsorbent for wastewater treatment would be a good re-use application for them, which would otherwise be landfilled directly after their generation.

Innovative pilot-scale constructed wetland-microbial fuel cell system for enhanced wastewater treatment and bioelectricity production

In this study, a unique configuration of pilot scale constructed wetland-microbial fuel cell (CW-MFC) system was evaluated in terms of chemical oxygen demand (COD) removal from synthetic wastewater and bioelectricity generation. The system consists of nine individual CW-MFC units and two aerobic chambers configured in a fibre-reinforced rectangular tank (Total working volume-135.5 L). Typha angustifolia was used as wetland plant. To enhance electrical performance of the system, two auxiliary MFCs equipped with terracotta-based separator-electrode-assembly (SEA) were integrated into the anodic zone of each CW-MFC unit in addition to the conventional sediment-configured MFC. The system was evaluated in fed-batch and continuous up-flow modes of operations. All the CW integrated MFCs were studied individually without any combinations (parallel/series). In fed-batch mode, the CW-MFC unit of the system removed a maximum of 97.56 ± 1.6 % of COD from wastewater. The highest power and current densities achieved by the auxiliary MFCs were 58.55 mW/m2 and 229.6 mA/m2 respectively. In the continuous up-flow mode, the pilot-scale system treated around 4100 L of wastewater and exhibited a maximum of 82.8 ± 1.9 % COD removal efficiency. Whereas, the auxiliary MFCs attained the maximum power and current densities of 41.44 mW/m2 and 283.3 mA/m2 respectively. In both modes, the internal resistance of the auxiliary MFCs was found to be two times lower than that of the conventional sediment-configured MFCs of the system. The overall results manifested that the inclusion of SEAs and aerobic chambers in this innovative pilot-scale CW-MFC shows merit and improved the energetics of the system.

Comparison of Dissolved Organic Matter Composition and Microbial Distribution between Distributed-Inflow Biological Reactor and Two-Stage Anoxic/Aerobic for Piggery Wastewater Treatment

Piggery wastewater contains high amounts of feces, carbon, nitrogen, phosphorus, and other contaminants, introducing serious pollution into water, soil, and the atmosphere. Biological treatment technology is widely used in large-scale pig farms because of its high efficiency and economical advantages. In this study, two typical biological treatment systems—a distributed-inflow biological reactor (DBR) and a two-stage anoxic/aerobic (A/O/A/O)—were adopted to treat piggery wastewater to compare the treatment performance, the dissolved organic matter (DOM) composition, and the microbial distribution characteristics. The results show that the A/O/A/O system had better removal performance in terms of chemical oxygen demand (COD) compared to the DBR system, and similarly effective at removing and ammonia nitrogen (NH4+-N) and total nitrogen (TN). Using parallel factor analysis of the fluorescence excitation–emission matrix, four DOM components—namely fulvic acid-like/humic-like substances (C1), tyrosine-like substances (C2), humic-like substances (C3), and tryptophan-like substances (C4)—were tracked in piggery wastewater. Protein-like substances were significantly degraded, while humic-like substances were difficult for microorganisms to utilize. The endogenous input and humus characteristics of effluents were enhanced. Bacteroidetes (43.9% and 37.5% ) and Proteobacteria (43.1% and 56.7%) are the dominant bacteria in DBR and A/O/A/O systems. The microbial metabolites in DBR and A/O/A/O systems are mainly composed of amino acids, sugars, alcohols, and other small molecules, while those in the municipal sewage treatment plant system is mainly composed of ketones, amines, acids, lipids, and other small molecules. The results of microbial communities and metabolites can help to trace the process of biological systems treating piggery wastewater.

Landfill leachate treatment by a combination of a multiple plant hybrid constructed wetland system with a solar photoFenton process in a raceway pond reactor

The sustainable and green treatment of landfill leachate (LL), produced by municipal solid waste, represents one of the most relevant challenges in the integrated waste management systems. Accordingly, in this work a green solution was investigated by coupling an innovative hybrid constructed wetland (HCW) to a solar photo-Fenton (SPF) process. A multiple layers HCW pilot plant including different medium substrates (sand, solid compost and carriers) and plant species (Phragmites australis, Arundo donax and A. plinii) was designed. The HCW was functionalised with compost tea solution to simultaneously provide high nutrient content for plants and increase the microorganism biodiversity. Process efficiency was investigated using different real LLs (young and mature) in terms of chemical oxygen demand (COD), nitrogen compounds, chlorides and metals. Removals in the range 75–95% were observed for all the parameters after ten days of leachate recirculation in the pilot plant. Subsequently, the SPF process was carried out in a raceway pond reactor (RPR) as polishing step, significantly improving COD removal (further 49%). HCW combined with SPF in RPR would allow to meet the corresponding limits according to the final use/fate of the effluent by modulating the main parameters of the process.

Enhanced Degradation of the Substrate Using Modified Upflow Anaerobic Sludge Blanket Reactor–Static Granular Bed Reactor Series with Varying Hydraulic Retention Time at Lab Scale

The performance of a modified upflow anaerobic sludge blanket (MUASB) reactor with a modified three-phase separator and a rope matrix, combined with SGBR in series was analyzed for the treatment of synthetic wastewater. The performance of the reactor series in terms of chemical oxygen demand (COD) removal was evaluated by varying the operational hydraulic retention times (HRT) from 12 to 30 h. The optimum HRT for the reactor series was found to be 24 h, with a corresponding organic loading rate (OLR) of 8 kg COD/m3/day. The maximum overall COD removal of the reactor series of 98.75% ±0.62% was obtained with the corresponding overall biogas production of 0.339%±0.01 m3/kg CODdigested. The reactor series was found to be stable during the operational period in terms of volatile fatty acids (VFAs)/alkalinity ratio. The analytical hierarchy process was used for choosing a better treatment option among the alternatives based on the selected criteria. MUASB–static granular bed reactor (SGBR) series was found to be superior to the MUASB and the SGBR individually based on COD removal. The payback period for the reactor series was calculated to be 8 years (approximately). The MUASB-SGBR series was found to be robust, stable, and economical, with better performance in terms of COD removal.

TİTANYUM DİOKSİT(TiO2) NANOPARTİKÜL MADDELERİN EVSEL ATIKSULAR ÜZERİNE UYGULANMASI: KİRLETİCİLERİN GİDERİMİ

Titanium is the ninth most abundant element in the earth's crust and is usually found in minerals such as rutile, ilmenite, and sphene. Adsorption, photocatalysis, and advanced oxidation processes are used in water and wastewater treatment. Among these processes, photocatalysis has emerged as a safe, efficient, and environmentally friendly treatment process for the treatment of wastewater with high pollutant content. Titanium dioxide (TiO2) is widely used as a photocatalyst and adsorbent. Titanium dioxide nanoparticle material has been applied in various fields, including environmental water and wastewater treatment. In this study, treatment performance was investigated by using TiO2 nanoparticles for the removal of pollutants in domestic wastewater. System performance was evaluated in terms of chemical oxygen demand (COD), dissolved organic carbon (DOC), and total nitrogen (TN). Different adsorbent concentrations (50-200 mg/L) and reaction times (15-90 min) were investigated at pH 7.2 to determine optimum conditions. Optimum adsorption concentration and reaction time were found to be 50 mg TiO2/L and 60 minutes, respectively. COD, DOC, and TN removal efficiencies were observed as 80%, 30%, and 35%, respectively. The obtained results showed that the removal efficiency of COD and DOC from domestic wastewater of TiO2 nanoparticles is high.

Application of electrocoagulation process for the treatment of dairy wastewater: A mini review

This review includes many studies of Electrocoagulation (EC) process in dairy wastewater (DWW) treatment and make comparison among these experimental results in absolute terms of chemical oxygen demand (COD) removal. To do that unit COD removal indicator (CODi-t) is calculated. Recently, EC technique gained immense attention due to its efficiency. The technique involves dissolution of the sacrificial anodes to provide an active metal hydroxide as a strong coagulant that destabilizes and amasses particles and then removes them by precipitation or adsorption. Conventional treatments are less efficient and are bulkier with less controllable parameter. This study reviews the effect of various operating parameter i.e. current density, electrolysis time, pH, conductivity, temperature, electrode material and gap on COD removal from the DWW. Some efforts are also given in design and economical aspect of EC process for particularly in dairy wastewater treatment. The characterization of the DWW of the reviewed articles has been analyzed to find suitability and advantages of the EC process in DWW treatment over the conventional treatment.

A natural microalgae consortium for the biological nutrient removal in a upflow photobioreactor as tertiary wastewater treatment

A natural microalgae consortium from a eutrophic lagoon was used and evaluated for the tertiary treatment in a upflow photobioreactor. The photobioreactor was continuously fed with the effluent of a UASB high-rate reactor. The photobioreactor average concentration of the inflow pre-treated wastewater in terms of chemical oxygen demand (COD), nitrogen (N), and phosphorus (P) was 125 mg/L, 49 mg/L, and 8 mg/L, respectively. The operation variables of the photobioreactor include a hydraulic retention time (HRT) of 1 day and 2 days of solids retention time (SRT). The photoperiod in the photobioreactor was 24 h at a light illuminance of 5000 lx. The highest nutrient uptake rates in the photobioreactor were 14 mg TN/L·d and 2 mg TP/L·d. Environmental conditions in the photobioreactor favour the cyanobacteria dominance over the microalgae taxonomic groups. In addition, the outcomes established CO2:N ratios of 9:1 to ensure the N removal in wastewater microalgae treatment systems.

Can microalgae grown in wastewater reduce the use of inorganic fertilizers?

Alternatives to conventional inorganic fertilizers are needed to cope with the growing global population and contamination due to the production and use of those inorganic compounds. The recovery of nutrients from wastewater and organic wastes is a promising option to provide fertilization in a circular economy approach. In this context, microalgae-based systems are an alternative to conventional wastewater treatment systems, reducing the treatment costs and improving the sustainability of the process, while producing nutrient-rich microalgal biomass. The aim of the present study is to evaluate the use of microalgal biomass produced during domestic wastewater treatment in high rate algal ponds as a biofertilizer in basil crops (Ocimum basilicum L.). Wastewater was successfully treated, with removal efficiencies in the secondary treatment of 69, 91 and 81% in terms of chemical oxygen demand (COD), total inorganic nitrogen (TIN) and phosphates (PO43–P), respectively. The microalgal biomass, composed mainly by Scenedesmus, presented the following composition: 12% of dry weight and nutrients concentration of 7.6% nitrogen (N), 1.6% phosphorus (P) and 0.9% potassium (K). The study compared the performance of 3 different fertilizers: 1) microalgae fertilizer (MF), 2) inorganic fertilizer (IF) as positive control and 3) the combination of both microalgae and inorganic fertilizer (MF + IF). Comparable plant growth (i.e., number of leaves, shoot fresh and dry weight and leaf fresh weight) was observed among treatments, except for leaf dry weight, which was significantly higher in the IF + MF and MF treatments (28 and 27%, respectively) in comparison with the control. However, the microalgae treatment provided the lowest chlorophyll, N and K leaf content. In conclusion, this study suggests that combining microalgae grown in wastewater with an inorganic fertilizer is a promising nutrients source for basil crops, enhancing the circular bioeconomy.