Chemical Oxygen Demand Efficiency Research Articles

Pilot–scale vertical continuous–flow reactors applied to treat rural domestic wastewater at low temperature via aerobic granular sludge

A pilot–scale vertical–flow continuous flow reactors (VF–CFR) was investigated for the treatment of rural domestic wastewater in the cold areas of Northeast China. VF–CFR helps in the creating of aerobic granular sludge (AGS), which improves the sludge concentration and removal efficiency of pollutants. VF–CFR achieved a high removal efficiency of Chemical Oxygen Demand (COD), Ammonia Nitrogen (NH3−N), Total Nitrogen (TN) and Total Phosphorus (TP) with 90 %, 94 %, 75 % and 93 % under the condition of sharp fluctuation of influent quality and temperature. The high–throughput sequencing analysis of the AGS revealed that Flavobacterium was a functional bacterium in the AGS process that had the function of heterotrophic nitrification and denitrification. The field–scale experiment confirmed the superiority of VF–CFR in wastewater treatment efficacy and stability. During the experiment, the concentrations of COD, TP and NH3–N in effluent at different temperatures were well met with the first–class A discharge standard of China (GB 18596–2001). However, there was a risk of exceedance exists in the reduction of TN removal under low temperature conditions.

Enhanced methane recovery from anaerobic membrane bioreactor coupled with cold plasma pretreatment for rapid hydrolysis and nitrogen removal

Research to increase biomethane recovery efficiency from thickened sewage sludge (TSWS) using sustainable anaerobic digestion (AD) in municipal wastewater treatment plants is ongoing. Pretreating substrates is known to increase organic biodegradation and biomethane conversion rates in AD. Cold plasma (CP), a recently adopted advanced oxidation processes (AOP) has emerged as an alternative to accelerate pretreatment times under different operation variables. This study assessed raw and CP-pretreated TSWS in an anaerobic sequencing batch reactor (ASBR) and anaerobic membrane bioreactor (AnMBR). The effects of incremental organic loading rates (OLR) and nitrogenous compounds concentration on enhanced CH4 bioconversion efficiency were evaluated. We found that the AnMBR outperformed the ASBR, with an overall chemical oxygen demand (COD) conversion rate of 67%, lower total nitrogen (T–N) accumulation (594 mg L−1), and an overall methane yield of 0.24 L CH4 g−1 COD. CP pretreatment improved TSWS AD, resulting in more efficient COD removal and methane recovery. This study suggests that CP technology is a promising pretreatment to improve AD when treating TSWS.

Loofah sponge crosslinked polyethyleneimine loaded with biochar biofilm reactor for ecological remediation of oligotrophic water: Mechanism, performance, and functional characterization

The removal of complex pollutants from oligotrophic water is an important challenge for researchers. In this study, the HCl-modified loofah sponge crosslinked polyethyleneimine loaded with biochar (LS/PEI@biochar) biofilm reactor was adapted to achieve efficient removal of complex pollutants in oligotrophic water. On the 35 d, the average removal efficiency of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), calcium (Ca2+), and phosphate (PO43--P) in water was 51, 95, 81, and 77 %, respectively. Additionally, it effectively used a low molecular weight carbon source. Scanning electron microscopy (SEM) results showed that the LS/PEI@biochar biocarrier had superior biofilm suspension performance. Meanwhile, analysis of the biocrystals confirmed Ca2+ and PO43- removal through the generation of CaCO3 (calcite and vaterite) and Ca5(PO4)3OH. This study demonstrated that the system has great efficiency and application prospect in treating oligotrophic water on the laboratory scale, and will be further validated for practical application on large-scale oligotrophic water.

Phytoremediation capability of Anabaena sp. for high organic and chromium-loaded wastewater in membrane bioreactors.

The efficiency of Anabaena sp. was analyzed for the phytoremediation of wastewater loaded with organic matter and heavy metals like chromium. Simulated wastewater was contaminated with chromium. A side-stream membrane bioreactor was used for the treatment of wastewater. A feed tank of 20 L capacity was used with a stirring arrangement. A ceramic microfiltration membrane composed of clay and alumina was obtained from Johnson & Johnson. The removal efficiency of chemical oxygen demand, biochemical oxygen demand, and chromium was evaluated. The process was used for algae harvesting and wastewater treatment. About 92% of chemical oxygen demand (COD), 98% chromium, and oil and grease were completely removed. Membrane fouling was explained by the pore blocking and cake resistance model. Stress in algal cells was determined from the superoxide dismutase (SOD) and catalase (CAT) analysis. The lipid content of algal cells was measured.

The role of fungi in the formation and instability of halophilic aerobic granular sludge in a continuous flow reactor

The role of fungi in aerobic granular sludge remains unknown. This study explored the formation and instability of halophilic aerobic granular sludge (HAGS) induced by fungi in a continuous flow reactor (CFR) figured with an aeration tank and a two-zone sedimentation tank. HAGS with a particle size of 420.10 ± 1.13 μm was successfully cultivated by increased hydraulic shear force (HSF). Increasing HSF stimulated microorganisms such as unclassified_f_Rhodobacteraceae, Muricauda, and Raineyella to secrete more extracellular polymeric substances (EPS) with a high protein (PN) content (81.03 ± 2.65 %). The peeled filamentous fungal fragments could act as colonization carriers to connect microorganisms. The mature HAGS had excellent removal efficiency of chemical oxygen demand (COD; 96.20 ± 1.19 %) and ammonia (92.13 ± 5.36 %) from 20 g/L saline wastewater. However, HAGS was disintegrated due to the fast growth of fungi, mainly unclassified_f_Nectriaceae, resulting in the deterioration of the sludge settling performance (SVI5 = 499.05 ± 7.80 mL/g). Filamentous fungi can use EPS secreted by bacteria under anaerobic and aerobic conditions. The excess EPS consumption finally destroyed the EPS and bacteria network. This study revealed the role of fungi in the formation and instability of HAGS in CFR, providing the basis for maintaining long-term HAGS stability.

Treatment of wet coffee processing wastewater using a pulsed-electrocoagulation process: optimization using response surface technique

In this study, the removal efficiency of chemical oxygen demand (COD), color, turbidity, phosphate, and nitrate from wet coffee processing wastewater by pulsed-electrocoagulation process (PECP) was examined with various factors such as pH: 3–11, reaction time: 15–75 min, current: 0.150–0.750 Amp, and electrolyte concentration: 0.25–1.25 g/L. Several operational parameters for the treatment of wet coffee processing wastewater utilizing the PECP have been optimized through the application of the surface response design technique, which is based on the central composite design. A quadratic model helped estimate the percentage removal of COD, color, turbidity, phosphate, and nitrate with power consumption under various situations. It also evaluated the significance and their interaction with independent variables using analysis of variance (ANOVA). Through the use of statistical and mathematical techniques, optimum conditions were determined in order to remove the maximum pollutant and nutrient while using the minimum of power. The results showed that the removal of COD—98.50%, color—99.50%, turbidity—99.00%, phosphate—99%, and nitrate—98.83%, with a power consumption of 0.971 kWh m−3 were achieved at pH-7, NaCl dose of 0.75 g/L, electrolysis duration of 45 min, and current of 0.45 Amp. Therefore, under the different operating conditions, the PECP demonstrated to be a successful technique for pollutant removal from wastewater and industrial effluent.

The performance of pharmaceutical wastewater treatment system of electrocoagulation assisted adsorption using perforated electrodes to reduce passivation.

The integrated electrocoagulation-assisted adsorption (ECA) system with a solar photovoltaic power supply has gained more attention as an effective approach for reduction chemical oxygen demand (COD) from pharmaceutical wastewater (PhWW). In this research, the ECA system was used for the treatment of PhWW.Several operating parameters were investigated, includingelectrode number, configuration, distance,operating time, current density, adsorption time, and temperature. Acurrent density of 6.656mA/cm2, sixelectrodes,a 20-mintime,a 4cm distance,an MP-Pconfiguration, anda 45 °C temperature produced the maximum COD reductions, where the operating cost of conventional energy was 0.273 $/m3. The EC, adsorption, and combination of EC and adsorption processes achieved efficient COD reductions of 85.4, 69.1, and 95.5%, respectively. The pseudo-second-order kinetic model and the Freundlich isotherm fitthe data of the endothermic adsorption process. Therefore, it was found that the combination processes were superior to the use of these processes in isolation to remove COD.

Degradation of 2,4-dinitrotoluene in aqueous solution by dielectric barrier discharge plasma combined with Fe–RGO–BiVO4 nanocomposite

2,4-Dinitrotoluene (2,4-DNT) as a priority and hazardous pollutant, is widely used in industrial and military activities. In this study the synergistic effect of Fe–RGO–BiVO4 nanocomposite in a non-thermal dielectric barrier discharge plasma reactor (NTP-DBD) for degrading 2,4-DNT was evaluated. Preparation of the Fe–RGO–BiVO4 nanocomposite was done by a stepwise chemical method depositing Fe and reduced graphene oxide (RGO) on BiVO4. Field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), UV–vis diffuse reflectance spectra (DRS), and energy-dispersive X-ray spectroscopy mapping (EDS-mapping) validated the satisfactory synthesis of Fe–RGO–BiVO4. To find the optimal conditions and to determine the interaction of model parameters, a central composite design (RSM-CCD) had been employed. 2,4 DNT can be completely degraded at: initial 2,4-DNT concentration of 40 mg L−1, Fe–RGO–BiVO4 dosage of 0.75 g L−1, applied voltage of 21kV, reaction time of 30 min and pH equal to 7, while the single plasma process reached a degradation efficiency of 67%. The removal efficiency of chemical oxygen demand (COD) and total organic carbon (TOC) were 90.62% and 88.02% at 30 min contact time, respectively. Results also indicated that average oxidation state (AOS) and carbon oxidation state (COS) were enhanced in the catalytic NTP-DBD process, which demonstrate the effectiveness of proposed process for facilitating biodegradability of 2,4-DNT.

Prediction of the removal of solid suspensions and chemical oxygen demand from a pharmaceutical wastewater plant using a neural network approach

This study aimed to model the removal efficiency of chemical oxygen demand (COD) and solid suspension (SS) from a real pharmaceutical wastewater treatment plant (WWTP) using artificial neural network-multilayer perception (ANN-MLP). The ANN model was developed using experimental data which were collected during four years. The input variables of the neural network are water pH, temperature, SS, and COD. The percentages of removal of COD (CODRE) and of SS (SSRE) are considered as output variables. The Levenberg–Marquardt algorithm was utilized to train ANN. It was found that the ANN architecture has two hidden layers with 8 neurons. The results of ANN models were compared with the measured data based on the correlation coefficient (R2) and mean square error (MSE). It was noticed that the best ANN model provides good accurate results with R2 values of 0.9783 for SSRE and 0.9826 for CODRE, and a value of MSE equal to 1.695 10−3. This study may aid the users to adjust operational parameters in recovering COD and SS in the case of the process treatment of industrial effluents.

Preparation of a coagulant of polysilicate aluminum ferric from foundry dust and its coagulation performance in treatment of swine wastewater

Polysilicate aluminum ferric (FD-PSAF) was prepared from foundry dust under polymerization temperature of 50 °C, polymerization time of 2 h and pH 2, to produce its amorphous Si–Al–Fe polymer. Removal efficiency of chemical oxygen demand (COD), color, turbidity and phosphate from swine wastewater reached 50.4%, 95.7%, 97.1% and 99.7% after addition of 10 mL/L of the prepared FD-PSAF, which were higher than those obtained when using polysilicate aluminum ferric (PSAF), polyaluminum chloride (PAC) and polymerized ferrous sulfate (PFS). The percentage content of Feb for PFS, PSAF and the prepared FD-PSAF was 7%, 11% and 24%, respectively. The mean particle size in the swine wastewater increased from 39 nm to 84 nm, 1003 nm, 1198 nm and 2138 nm respectively after the addition of PSAF, PAC, PFS and prepared FD-PSAF into the swine wastewater. The prepared FD-PSAF with the higher coagulation performance could be related to its higher percentage content of Feb and greater particle aggregation ability. The removal efficiency of color, turbidity and phosphate from swine wastewater by FD-PSAF did not obviously change with storage time from 1 d to 32 d, indicating that FD-PSAF had good stability performance. The FD-PSAF is an efficient coagulant that could be used to treat swine wastewater.

TREATMENT OF LEACHATE FROM ERBIL LANDFILL SITE BY ELECTRO- AND CHEM-ICAL COAGULATION METHODS

Landfill leachate is commonly heavily contaminated wastewater. and consists of a high number of organic compounds, inorganic salts, toxic gases and heavy metals that exert a serious threat to the environment and public health. Thus, it requires treatments before direct release into receiving waters.  This paper presents the results of electrocoagulation (EC) and chemical coagulation (CC) treatment of leachate from the Erbil landfill site. The removal efficiency of chemical oxygen demand (COD), phosphate (PO43-), total suspended solids (TSS), total organic compound (TOC), and color of leachate was studied using iron and aluminum electrodes. The removal percentages were also compared to those produced by electrochemically generated Fe2+ and Al3+ dosages. The effect of different pH values on the removal efficiency of these parameters was evaluated at optimal conditions. The removal percentages for chemically added coagulants were lower than those for electrochemically generated Fe2+ and Al3+. In EC, the highest COD removal efficiency of 92% and 87% was achieved at the original concentration (C1) for iron and aluminum electrodes, respectively. The iron and aluminum electrodes also showed a maximum color removal of 90% and 95%, respectively, for the original undiluted leachate solution. Both Fe and Al electrocoagulation methods were not effective in removing TOC from the leachate of municipal solid waste. The highest removal efficiency of 78% was achieved at a 1:4 diluted solution (C2) using the Al-electrocoagulation method. The maximum removal percentage for PO43- was 94% at C1 using the Fe-electrocoagulation system. However, both systems were not very effective in removing TSS.

Copper Nanoparticles Coupled with Fine-Powdered Active Carbon-Modified Ceramic Membranes for Improved Filtration Performance in a Membrane Bioreactor

Membrane fouling is a key factor limiting the application of a membrane bioreactor (MBR), and membrane-surface modification holds the potential to control membrane fouling and solves this problem. In the research, novel nanocomposite membranes were designed and fabricated using antimicrobial copper nanoparticles (CuNPs) coupled with powdered active carbon (PAC) to mitigate membrane fouling. The successful coating was confirmed by SEM, XRD, and FTIR analysis. Compared with a pristine membrane, the functionalization of CuNPs and PAC improved the hydrophilicity of the modified membrane but led to a lower permeate flux. The result of antimicrobial adhesion experiments showed that the modified M-CuOC displayed high antibacterial activity with the bacteria count decreased by 72%. In MBR operation, the modified M-CuOC leads to the removal efficiency of chemical oxygen demand (COD) increasing to 93%, with better filtration performance under a lower TMP rise. The fouling-resistance analysis demonstrated that, although the intrinsic membrane resistance of modified M-CuOC slightly increased, the reversible and irreversible fouling resistances obviously decreased by 45% and 90%. Moreover, the membrane flux recovery efficiency of the modified M-CuOC also increased by 35%. Overall, these results indicated that, in addition to an improvement in antifouling performance, the functionalization of CuNPs and PAC also enhanced the membrane flux recovery efficiency, revealing a good antifouling potential in a practical application.

Supplementation of strigolactone analog for enhancing the removal of nutrient and heavy metal by microalgae-fungi symbionts

The purification effects of Chlorella vulgaris and Chlorella vulgaris-Clonostachys symbionts on nutrients and heavy metals in wastewater were investigated to determine the optimal symbiotic treatment technology and the suitable concentration of GR24. The results showed that exogenous GR24 not only promoted the formation of uniform green spheres in microalgae-fungi symbionts, but also increased its photosynthetic performance and growth. At 10−7 M GR24 addition concentration, the specific growth rate of microalgae-fungi symbionts was 0.367 ± 0.04 d−1, the maximum removal efficiency of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were 81.96 ± 7.93 %, 80.26 ± 7.91 % and 82.96 ± 8.05 %, respectively. When the concentration of exogenous GR24 was 10−5 M, the removal efficiency of heavy metals was the best at both low and high pollution levels. It was worth noting that the removal efficiency of Zn at low concentration pollution levels (1 mg L−1) was 99.32 ± 0.43 %, nearly 100 %. This study promoted the development of microalgae-fungal symbionts in the field of wastewater treatment.

Enhancement of carbon nanotubes on microalgal-fungal consortium formation and wastewater treatment

As a promising material with an efficient light capture capability, a low amount of carbon nanotubes can affect growth and photosynthesis by regulating microalgal cells, thereby enhancing the pollutant removal efficiency in wastewater. In this study, microalgal-fungal consortia of Chlorella vulgaris and Ganoderma lucidum were developed with different types and concentrations of carbon nanotubes. The treatment effect of microalgal-fungal consortia on simulated digestate was also studied. The results demonstrate that 1.5 mg/L of carboxylated multi-walled carbon nanotubes remarkably promoted the formation, growth and photosynthesis of consortium. The dry weight and chlorophyll a content reached 19.3 ± 0.53 mg/symbiont and 27.3 ± 0.52 μg/L, respectively. Moreover, the removal efficiency of chemical oxygen demand, total nitrogen, total phosphorus and tetracycline hydrochloride were 94.1%, 65.5%, 61.9% and 96.2%, respectively. Overall, these findings suggest a promising future for the use of carbon nanotubes in wastewater treatment by regulating microalgal-fungal consortia.

Experimental study of microwave-catalytic oxidative degradation of COD in livestock farming effluent by copper-loaded activated carbon

ABSTRACT The problem of massive discharge of livestock wastewater is becoming more and more severe, causing irreversible damage to the ecological environment, and how to treat livestock wastewater efficiently and rapidly deserves to be studied in depth. In this work, CuO/granular activated carbon (GAC) loaded catalysts were prepared and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption/desorption techniques, and X-ray energy spectroscopy (EDS). The results showed that CuO was successfully attached to the GAC surface with good adsorption performance. The effects of catalyst dosage, H2O2 dosage, initial pH, microwave power and microwave irradiation time in different reaction systems on the degradation efficiency of chemical oxygen demand (COD) in wastewater were investigated, and the orthogonal experiments were used to explore the importance ranking of these factors. The highest degradation rate of COD was found to be enhanced by 12.1% in the reaction system of CuO/GAC, and the initial pH had the greatest effect on the COD removal rate. The combined MW/catalyst/H2O2 method used in this work provided a rapid and effective degradation of COD in wastewater, which can be helpful for reference in other microwave catalytic oxidation studies.

Effect of mariculture wastewater concentrations on high-value production and pollutants removal with bacterial-algal coupling reactor (BACR)

To achieve the goal of cost-effective mariculture wastewater treatment, a novel Bacteria-Algae Coupling Reactor (BACR) integrating acidogenic fermentation with microalgae cultivation was applied for the mariculture wastewater treatment. Currently, there is limited research on the impact of different concentrations of mariculture wastewater on the pollutant removal and the high-value products recovery. In this study, different concentrations (4, 6, 8, and 10 g/L) of mariculture wastewater were treated with BACR. The results showed thatoptimalMW concentrations of 8 g/L improved the growth viability and biochemical components synthetic of Chlorella vulgaris, which increased the potential for high-value products recovery. The BACR exhibited the excellent removal efficiency of chemical oxygen demand, ammonia–nitrogen and total phosphorus with 82.30%, 81.12% and 96.40%, respectively. This study offers an ecological and economic approach to improve the MW treatment through the utilization of a novel bacterial-algal coupling system.

Synergistic effect of adsorption and photocatalytic degradation of oilfield-produced water by electrospun photocatalytic fibers of Polystyrene/Nanorod-Graphitic carbon nitride

Graphitic carbon nitride with nanorod structure (Nr-GCN) was synthesized using melamine as a precursor without any other reagents by hydrothermal pretreatment method. XRD, FTIR, SEM, N2 adsorption-desorption from BET, UV–Vis DRS spectroscopy, and photoluminescence were used to characterize the prepared samples. Also, the photoelectrochemical behavior of nanoparticles was studied by photocurrent transient response and cyclic voltammetry analysis. Polystyrene (PS) fibrous mat was fabricated by electrospinning technique and used as a support for the stabilization of the nanoparticles. The performance of the synthesized nanoparticles and photocatalytic fibers (PS/Nr-GCN) was evaluated in oilfield-produced water treatment under visible light irradiation. During this process, oil contaminants were adsorbed by hydrophobic polystyrene fibers and simultaneously degraded by Nr-GCN. The removal efficiency of chemical oxygen demand (COD) has been obtained 96.6% and 98.4% by Nr-GCN and PS/Nr-GCN, respectively, at the optimum conditions of pH 4, photocatalyst dosage 0.5 g/L, COD initial concentration 550 mg/L, and illumination time 150 min. The gas chromatography-mass spectroscopy analysis results showed 99.3% removal of total petroleum hydrocarbons using photocatalytic fibers of PS/Nr-GCN. The results demonstrated that the GCN has outstanding features like controllable morphology, visible-light-driven, and showing high potential in oily wastewater remediation. Moreover, the synergistic effect of adsorption and photocatalytic degradation is an effective technique in oilfield-produced water treatment.

Evaluation of persulfate enhanced electrocoagulation (EC/PS) for bio-treated landfill leachate: Organics transformation pathways and carbon flow quantitative analysis

The sulfate radical-based advanced oxidation processes (SR-AOPs) have shown promise in treating bio-treated landfill leachate (BLL). However, little is known about the dissolved organic matter (DOM) transformation and reaction mechanisms at the molecular level after treating BLL using SR-AOPs. This study investigates the DOM degradation and transformation pathways during both electrocoagulation (EC) and persulfate enhanced electrocoagulation (EC/PS) of real BLL samples. The results indicate that the removal efficiency of chemical oxygen demand (COD) and total organic carbon (TOC) were enhanced to 46.34% and 36.39%, respectively, once persulfate is coupled with EC. Additionally, the removal of fluorescent contaminants in BLL significantly enhanced after treatment with EC/PS to 91.57%, 80.99%, and 39.10% for biogenic humic-like components C1, C2, and C3, respectively. A decrease in the proportion of macromolecular and aromatic matters was observed after the EC/PS process. The degree of oxidation of DOM was reduced, and the compounds with unstable structure and high biodegradability became the main compounds in the EC/PS effluent. The analysis of sediments generated by EC and EC/PS showed a similar composition of FeOOH and Fe3O4, although there was additional Fe2(SO4)3 in the EC/PS sludge. The degraded organics in the solution and sediment phase were quantified by material flow analysis, indicating that the precipitation was the main contributor to DOM removal during the EC/PS process. These findings aid in understanding the role of PS in the EC/PS process during real landfill leachate treatment and reevaluate the advantages and limitations of PS as an oxidant.

Highly reusable bentonite clay@biochar@Fe3O4 nanocomposite for Hg(II) removal from synthetic and real wastewater.

The present research investigates the performance of bentonite clay@biochar@Fe3O4 nanocomposite in removing mercury ions (Hg2+) from aqueous media. The physical and structural properties of bentonite clay@biochar@Fe3O4 were determined using Brunauer-Emmett-Teller (BET), vibrating-sample magnetometer (VSM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and Raman analyses. The highest uptake efficiency of Hg2+ was obtained at pH 6, Hg2+ concentration of 10 mg/L, contact time of 80 min, and the composite dose of 1.5 g/L. Under these conditions, the uptake efficiency of bentonite clay@biochar@Fe3O4 and bentonite clay was obtained as 98.78% and 97.67%, respectively, which are remarkable values. Also, the qmax values in Hg2+ removal using bentonite clay@biochar@Fe3O4 and bentonite clay were obtained as 66.66 and 60.98 mg/g, respectively. Moreover, the uptake process of Hg2+ ions using bentonite clay@biochar@Fe3O4 nanocomposite and bentonite was spontaneous, physical, favorable, and exothermic. Besides, the impact of various divalent ions such as Co2+, Cu2+, Pb2+, Ni2+, and Zn2+ on the removal efficiency of Hg2+ was studied. The results showed that Co2+ and Zn2+ ions have the highest and lowest interference effect in Hg2+ removal, respectively. Also, the reusability of both adsorbents showed that they have high stability and can be used for at least 5 cycles with high uptake efficiency. Additionally, the removal efficiency of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), Hg2+, As3+, and As5+ from real wastewater using bentonite clay@biochar@Fe3O4 was obtained as 37.5%, 28.9%, 65%, 60.5%, and 50%, respectively, indicating its remarkable performance.

Investigation of a basic nitrification–denitrification biofiltration system for primary wastewater treatment

Abstract The study aimed to eliminate the nitrogen and its main residual forms from municipal wastewater by using a biofilter system adapted for a small community. The biological nitrification/denitrification system used involved two successive PVC columns; a first gravel column (C1) loaded with primary wastewater followed by a second sandy column (C2). A complex biofilm development on the gravel and sand materials has been confirmed by scanning electron microscope. The efficiency of chemical oxygen demand (COD), BOD5, TSS, and NH4+-N removal from primary wastewater reached 75.3, 88.4, 83.5, and 88.1%, respectively, at the exit of the sandy column (C2). Inoculation with activated sludge as an external carbon source allowed an improvement in the nitrate removal, from 80 to 28 mg/l N-NO3. However, sludge inoculation showed non-significant fecal coliforms and Streptococcus contamination, and the biofilter appeared as effective for total nitrogen removal and a bacterial abatement of over 3.2 U-log10. The average bacterial removal seemed directly related to the applied load of about 50 cm/day and a tertiary disinfection treatment, such as UV-C254 irradiation, is needed as a preventive step to ensure the removal of pathogens.