Boosting environmental remediation: harnessing the efficiency of graphitic carbon nitride stabilized on red ocher surface for enhanced photocatalytic remove of Escherichia coli.

In the present study, the antibacterial effect of graphitic carbon nitride coated on the red ocher was investigated by the photocatalytic process to remove Gram-negative Escherichia coli bacteria. The concentration effects (0.025, 0.05, and 0.1 g/mL) of disinfectant, contact time (30, 60, and 90 min), and the number of bacteria (102, 104, and 106 CFU/mL) were examined. In this research, in each experiment, 100 mL of the sample was taken, and the test work was performed. The red ocher required for this project was obtained from Hormoz Island, Hormozgan Province, Iran. Melamine was used for the synthesis and manufacture of graphitic carbon nitride. A general-purpose media was used for microbial culture using the pour and spread plate methods, as well as an LED lamp with a wavelength of 420 nm as a light source for the photocatalytic process. To obtain the important factors, the interaction of the factors and the optimal experimental design were used through the response surface methodology (RSM) based on the Box-Behnken design. According to research findings, this method is effective in eliminating E. coli. The results showed that the increase in the amount of disinfectant from 0.025 to 0.1 g/mL and also the increase of contact time from 30 to 90 min accelerated the removal rate of E. coli. The numerical value of R2 obtained for the removal of E. coli was 0.9728, indicating good agreement between experimental and predicted data. Therefore, its utilization in water disinfection seems necessary, both to ensure human health and environmental protection.

Ammonia removal from industrial effluent using zirconium oxide and graphene-oxide nanocomposites.

The present study developed and evaluated nano-adsorbents based on zirconium oxide and graphene oxide (ZrO2/GO) as a novel adsorbent for the efficient removal of ammonia from industrial effluents. Fourier transform infrared (FTIR) spectroscopy, Field Emission Scanning Electron Microscope, Energy-dispersive X-ray Spectroscopy, and X-ray diffraction were used to evaluate and identify the novel adsorbent in terms of morphology, crystallography, and chemical composition. The pH (7), adsorbent quantities (20 mg), adsorbent contact time (30 min) with the sample, and initial ammonia concentration were all tuned for ammonia uptake. To validate ammonia adsorption on the ZrO2/GO adsorbent, several kinetic models and adsorption isotherms were also utilized. The results showed that the kinetics of ammonia adsorption are of the pseudo-second order due to high R2 (>0.99) value as compared first-order (R2 = 0.52). The chemical behavior and equilibrium isotherm were analyzed using the isotherm models and Langmuir model provided high R2 (>0.98) as compared Freundlich (>0.96). Hence, yielding a maximum uniform equilibrium adsorption capacity of 84.47 mg g-1. The presence of functional groups on the surface of graphene oxide and ZrO2 nanoparticles, which interact efficiently with ammonia species and provide an efficient surface for good ammonia removal, is most likely to be responsible.

The thermodynamic stability, potential toxicity, and speciation of metals and metalloids in Tehran runoff, Iran.

Surface runoff is the most significant source of water in dry cities like Tehran. The surface runoff is polluted by heavy metals, which their risk level is a function of their speciation. Herein, Tehran runoff quality and the speciation of metals and metalloids were investigated. The results of quality showed that oxidation-reduction potential (Eh) and pH ranged from + 186 to + 230 mV and from 7.31 to 10.29, respectively. Cluster analysis indicated that Cr, Si, Mn, Fe, Pb, Se, Th, Ba, Ni, Li, and Sr had similar behaviors and origins, and salinity played an active role in restricting their concentrations. Eh and dissolved oxygen (DO) negatively affected the concentrations of all the studied elements. The speciation model (according to HSC Chemistry program) exhibited that all the studied elements are stable; however, in two cases, they would become unstable (pH < 7, Eh < - 480 mV or Eh > 1100 mV) and (pH > 10, Eh < - 570 mV or Eh > 970 mV). Also, Ba, Cd, Li, Mn, Al, As, Sr, Cr, Si, and Se are present in bioavailable species and As and Cd in the runoff exist in high toxic oxidation states of + 3 and + 2, respectively. The linear regression of Cu, Co, Cd, Zn, and As with Eh provided a good fit, and all of these metals were significant at levels 1 and 5%. Finally, it is recommended to continuously monitor the Eh-pH changes for investigating the potential toxicity of metals and predicting the metal pollution by regression equations in any other stations.

Waste plastic filter modified with polyaniline and polypyrrole nanoparticles for hexavalent chromium removal.

Chromium (Cr) is a toxic heavy metal for environmental compartments and human health. In this study, waste polypropylene hollow filters (PPF) with an optimal pore size of 5 µm were amino-functionalized with an optimized amount of polyaniline (PANI) and polypyrrole (PPy) as an adsorbent for removing Cr (VI). The adsorbent was characterized by scanning electron microscope, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and the Brunauer-Emmett-Teller method, showing the successful polymerization of co-polymer on the surface of PPF and increasing the surface area up to 15.08 m2 g-1. A Box-Behnken design was applied by a quadratic model with 99.15% accuracy, revealing a significant impact of the initial concentration of Cr (VI) on the removal efficiency. Dynamic adsorption was conducted in a continuous and semi-continuous system with over 99% removal efficiency for various initial concentrations of Cr(VI). The fitted data showed that the adsorption process followed the pseudo-second-order kinetics and Langmuir isotherm models at the optimum pH of 2 with the predicted maximum adsorption capacity of 510.9 mg g-1 of PANI+PPy, which was significantly higher than some reported adsorbents. The effect of coexisting cations (Cu2+, Ni2+, and Zn2+) and anions (SO42-, Cl- and NO3-) on the removal efficiency revealed selective adsorption of Cr(VI) by the adsorbent. The produced adsorbent was capable of removing 76.6% of Cr(VI) from real electroplating wastewater. Regeneration of the adsorbent was performed by NaOH 1 mol L-1 up to three cycles with a 20% reduction in adsorption performance. All data showed that PPF@PANI+PPy was a promising adsorbent for Cr(VI) removal from aqueous solutions and real-world wastewater.

Synthesis of sewage sludge-based carbon/TiO2 /ZnO nanocomposite adsorbent for the removal of Ni(II), Cu(II), and chemical oxygen demands from aqueous solutions and industrial wastewater.

The removal of heavy metal ions and organic materials from wastewater due to their toxicity is necessary. In the present study, the titanium dioxide/zinc oxide (TiO2 /ZnO) nanocomposite has been coated on the sewage sludge carbon (SSC) surface and its application was investigated for the adsorption of Ni(II), Cu(II), and chemical oxygen demands (COD) reduction from aqueous solutions and industrial wastewaters in Eshtehard, Iran. The effect of adsorption parameters in a single system such as TiO2 /ZnO ratio, TiO2 /ZnO concentration, pH, adsorbent dosage, contact time, ionic strength, temperature, and initial concentrations of Ni(II), Cu(II), and COD was investigated on the adsorption capacity of synthesized SSC/TiO2 /ZnO adsorbent. The pseudo-second order and Redlich-Peterson isotherm models were best described the kinetic and equilibrium data of Ni(II), Cu(II), and COD sorption. The maximum monolayer sorption capacities of Ni(II), Cu(II), and COD were found to be 62.3, 75.1, and 1,120.3 mg/g, respectively. The central composite design was used to investigate the interaction effects of pH and initial concentrations of Ni(II), Cu(II), and COD on the simultaneous removal of Ni(II), Cu(II), and COD from aqueous solutions in a ternary system. The potential of synthesized SSC/TiO2 /ZnO adsorbent was investigated for Ni(II), Cu(II), and COD adsorption from industrial wastewaters of Iran. PRACTITIONER POINTS: The novel sewage sludge carbon/TiO2 /ZnO adsorbent was synthesized. Adsorption of Ni(II), Cu(II), and chemical oxygen demands (COD) from industrial wastewaters was investigated. Maximum Ni(II), Cu(II), and COD sorption capacities were 62.3, 75.1, and 1,120.3 mg/g. Simultaneous removal of Ni(II), Cu(II), and COD was investigated in a ternary system.

Improvement and prediction of OSA system performance in sludge reduction through integration with thermal and mechanical treatment.

The oxic-settling-anoxic (OSA) process is one of the sludge production reduction methods in the activated sludge process. In this method, sludge is stored in an anaerobic tank within the sludge return line before entrance into an aeration tank. Due to this method's flexibility in application to operating treatment plants and not being energy-consuming, its application is developing. In this research, the improvement of the OSA process is investigated via thermal and mechanical treatment in a sequencing batch reactor (SBR). A pilot-scale reactor and domestic wastewater are used. Sludge was subjected to high temperature in an anaerobic tank using a heat transformer and it was subjected to mechanical shear through mechanical mixing in the anaerobic tank. Different temperatures and voltages were tested. The OSA process reduced sludge production by 24% while the chemical oxygen demand (COD) removal rate decreased from 90% to 86%. Thermal treatment combined with the OSA process caused a maximum of 46% sludge production reduction. However temperatures above 90 °C are not recommended due to a high level of decrease in COD removal. Mechanical mixing in combination with the OSA process led to 34% sludge production reduction. The effluent quality is not affected by the OSA process itself but is slightly reduced by thermal treatment and mechanical mixing. Therefore, for reaching the maximum sludge reduction in OSA plus thermal and mechanical treatment it would be necessary to evaluate the effect of different sets of parameters on effluent quality beside the sludge reduction. For this purpose multi-layer perceptron artificial neural network models are developed to predict the effluent total suspended solids and COD removal efficiency as well as sludge production rate. The models perform well and would be useful tools in determining the optimal set of system operation parameters.

A new flat sheet membrane bioreactor hybrid system for advanced treatment of effluent, reverse osmosis pretreatment and fouling mitigation.

This paper introduces a new hybrid electro membrane bioreactor (HEMBR) for reverse osmosis (RO) pretreatment and advanced treatment of effluent by simultaneously integrating electrical coagulation (EC) with a membrane bioreactor (MBR) and its performance was compared with conventional MBR. Experimental results and their statistical analysis showed removal efficiency for suspended solids (SS) of almost 100% for both reactors. HEMBR removal of chemical oxygen demand (COD) improved by 4% and membrane fouling was alleviated according to transmembrane pressure (TMP). The average silt density index (SDI) of HEMBR permeate samples was slightly better indicating less RO membrane fouling. Moreover, based on the SVI comparison of two reactor biomass samples, HEMBR showed better settling characteristics which improved the dewaterability and filterability of the sludge. Analysis the change of membrane surfaces and the cake layer formed over them through field emission scanning electron microscopy (FESEM) and X-ray fluorescence spectrometer (XRF) were also discussed.

Synthesis, modification and graft polymerization of magnetic nano particles for PAH removal in contaminated water.

Magnetic nanoparticles (MNPs) were modified with 3-Mercaptopropytrimethoxysiline (MPTMS) and grafted with allyl glycidyl ether for coupling with beta naphtol as a method to form a novel nano-adsorbent to remove two poly aromatic hydrocarbons (PAHs) from contaminated water. The modified MNPs were characterized by transmission electron microscopy, infrared spectroscopy and thermogravimetric analysis. Results showed that the modified MNPs enhanced the process of adsorption. Tests were done on the adsorption capacity of the two PAHs on grafted MNPs; factors applied to the tests were temperature, contact time, pH, salinity and initial concentration of PAHs. Results revealed that adsorption equilibrium was achieved in 10 min, and the maximum adsorption capacity was determined as 4.15 mg/g at pH = 7.0 and 20°C. The equilibrium adsorption data of the two PAHs by the modified MNPs were analyzed by Langmuir, Freundlich and Temkin models. Equilibrium adsorption data was determined from the Langmuir, Freundlich and Temkin constants from tests under conditions of pH = 7 and temperature 20°C. Analysis of the adsorption-desorption process indicated that the modified MNPs had a high level of stability and good reusability. Magnetic separation in these tests was fast and this shows that the modified MNPs have great potential to be used as a new adsorbent for the two PAHs removal from contaminated water in water treatment.

Attenuation of municipal landfill leachate through land treatment.

The treatment of municipal landfill's leachate is considered as one of the most significant environmental issues. In this study a laboratory experiment was conducted through land treatment, achieving an efficient and economical method by using Vetiver plant. Moreover, the effects of land treatment of leachate of municipal landfills on the natural reduction of organic and inorganic contaminants in the leachate after the pre-treatment in the Aradkouh disposal center are invested. Three pilots including the under-investigation region's soil planted by Vetiver plant, the region's intact soil pilot and the artificial composition of the region's soil including the natural region's soil, sand, and rock stone are used. The leachate, having passed its initial treatment, passed through the soil and to the pilot. It was collected in the end of the pilots and its organic and inorganic contaminants were measured. However, the land treatment of leachate was conducted in a slow rate at various speeds. According to the results, in order to remove COD, BOD5, TDS, TSS, TOC the best result was obtained in the region's soil planted with Vetiver plant and at the speed of 0.2 ml per minute which resulted 99.1%, 99.7%, 52.4%, 98.8%, 94.9% removal efficiencies, respectively. It also can be concluded that the higher the organic rate load is, the lower the efficiency of the removal would be. In addition, EC & pH were measured and the best result was obtained in the region's soil planted with Vetiver plant and at the speed of 0.2 ml/min.

Evaluation of membrane bioreactor for advanced treatment of industrial wastewater and reverse osmosis pretreatment.

The evaluation of a membrane bioreactor (MBR) for pretreatment of reverse osmosis (RO) in order to reuse and reclamation of industrial town wastewater treatment plant was investigated in this study. Performance of MBR effluent through water quality in term of parameters such as chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN) and total coliform (TC) were measured. Also Silt density index (SDI) was used as indicator for RO feed water. The results of this study demonstrated that MBR produce a high quality permeate water. Approximately 75%, 98%, 74% and 99.9% removal of COD, TSS, TN and TC were recorded, respectively. Also SDI of the permeate effluent from membrane was below 3 for most of the times. It means that pilot yield a high quality treated effluent from the membrane module which can be used as RO feed water.

Application of an anaerobic hybrid reactor for petrochemical effluent treatment.

An anaerobic hybrid reactor (UASB/Filter) was used for petrochemical wastewater treatment in mesophilic conditions. The seeded flocculent sludge from a UASB plant treating dairy wastewater, acclimatized to the petrochemical wastes in a two-stage operation. After start up, under steady-state conditions, experiments were conducted at OLRs of between 0.5 and 24 kg TCOD m(-3) d(-1), hydraulic retention times (HRT) of 4-48 h and up-flow velocities 0.021-0.25 mh(-1). Removal efficiencies in the range of 42-86% were achieved at feed TCOD concentrations of 1,000-4,000 mg L(-1). The results of reactor performance at different operational conditions and its relations are presented and discussed in this paper. Then, the obtained data are used for determination of kinetic models. The results showed that a second-order model and a modified Stover-Kincannon model were the most appropriate models for this reactor. Finally, the biogas production data were used for the determination of biogas production kinetics.

Water pinch analysis for water and wastewater minimization in Tehran oil refinery considering three contaminants.

This study aims to find an appropriate way to minimize water utility in the petrochemical and petroleum industries due to high rate of water consumption. For this purpose, Tehran oil refinery has been well studied. In this research, three key contaminants including suspended solid, hardness as well as COD have been considered to analyze the water network. In addition, the potential of water reuse was studied for all methods. These key contaminants once were analyzed separately as a single contaminant and the amount of required freshwater was calculated for them. In this stage, amount of freshwater was reduced to about 60.9 (17%), 203 (59.7%) and 143 m(3)/h (42.5%) in terms of suspended solids, hardness, and COD, respectively. Water minimization within operations for suspended solids is less than two others. Therefore, this is a limiting contaminant and can be selected as a key contaminant. In the next stage, three contaminants were analyzed two by two based on their mass transfer. Results show that, in the targeting for minimization based on the suspended solids and hardness, the amount of required water is reduced to 142.74 m(3)/h or 42%. This amount for suspended solids and COD is equal to 86.3 m(3)/h (26%) and for COD and hardness is 124 m(3)/h (37%). Analyzing the methods shows that the method based on the double contaminant gives more precise results rather than single contaminant.

Simultaneous nitrification-denitrification and phosphorus removal in a fixed bed sequencing batch reactor (FBSBR).

Biological nutrient removal (BNR) was investigated in a fixed bed sequencing batch reactor (FBSBR) in which instead of activated sludge polypropylene carriers were used. The FBSBR performance on carbon and nitrogen removal at different loading rates was significant. COD, TN, and phosphorus removal efficiencies were at range of 90-96%, 60-88%, and 76-90% respectively while these values at SBR reactor were 85-95%, 38-60%, and 20-79% respectively. These results show that the simultaneous nitrification-denitrification (SND) is significantly higher than conventional SBR reactor. The higher total phosphorus (TP) removal in FBSBR correlates with oxygen gradient in biofilm layer. The influence of fixed media on biomass production yield was assessed by monitoring the MLSS concentrations versus COD removal for both reactors and results revealed that the sludge production yield (Y(obs)) is significantly less in FBSBR reactors compared with SBR reactor. The FBSBR was more efficient in SND and phosphorus removal. Moreover, it produced less excess sludge but higher in nutrient content and stabilization ratio (less VSS/TSS ratio).

Optimizing aeration rates for minimizing membrane fouling and its effect on sludge characteristics in a moving bed membrane bioreactor.

In MBR processes, sufficient aeration is necessary to maintain sustainable flux and to retard membrane fouling. Membrane permeability, sludge characteristics, nutrient removal and biomass growth at various air flow rates in the membrane and moving bed biofilm reactor (MBBR) compartments were studied in a pilot plant. The highest nitrogen and phosphorous removal rates were found at MBBR aeration rates of 151 and 85 L h(-1) and a specific aeration demand per membrane area (SAD(m)) of 1.2 and 0.4 m(air)(3) m(-2) h(-1), respectively. A linear correlation was found between the amount of attached biofilm and the nutrient removal rate. The aeration rate in the MBBR compartment and SAD(m) significantly influenced the sludge characteristics and membrane permeability. The optimum combination of the aeration rate in the MBBR compartment and SAD(m) were 151 L h(-1) and 0.8-1.2 m(air)(3) m(membrane)(-2) h(-1), respectively.