Problems due to the taste and odor in drinking water are common in treatment facilities around the world. Taste and odor are perceived by the public as the primary indicators of the safely and ...acceptability of drinking water and are mainly caused by the presence of two semi-volatile compounds − 2-methyl isoborneol (MIB) and geosmin. A review of these two taste and odor causing compounds in drinking water is presented. The sources for the formation of these compounds in water are discussed alongwith the health and regulatory implications. The recent developments in the analysis of MIB/geosmin in water which have allowed for rapid measurements in the nanogram per liter concentrations are also discussed. This review focuses on the relevant treatment alternatives, that are described in detail with emphasis on their respective advantages and problems associated with their implementation in a full-scale facility. Conventional treatment processes in water treatment plants, such as coagulation, sedimentation and chlorination have been found to be ineffective for removal of MIB/geosmin. Studies have shown powdered activated carbon, ozonation and biofiltration to be effective in treatment of these two compounds. Although some of these technologies are more effective and show more promise than the others, much work remains to be done to optimize these technologies so that they can be retrofitted or installed with minimal impact on the overall operation and effectiveness of the treatment system.
Occurrence and frequency of six most prescribed antibiotics (tetracycline, norfloxacin, azithromycin, anhydro erythromycin, cephalexin, and amoxicillin) were assessed in three wastewater treatment ...plants (WWTPs), and in water and sediments of the Persian Gulf at Bushehr coastline, Iran. The antibiotics concentration in the influent and effluent of septic tank (the hospital WWTP), activated sludge (the hospital WWTP), and stabilization pond (municipal WWTP) ranged between 7.89 and 149.63, 13.49–198.47, 6.55–16.37 ng/L, respectively. Conventional treatment resulted in incomplete removal of most of the studied antibiotics. Furthermore, the activated sludge was more effective in terms of antibiotic elimination compared to the stabilization pond or septic tank. The mean concentration of antibiotics ranged 1.21–51.50 ng/L in seawater and 1.40–25.32 ng/g in sediments during summer and winter. Norfloxacin was the dominant detected antibiotic in seawater, sediments, and influent of two hospital WWTPs. Seasonal comparisons showed significant differences for erythromycin and amoxicillin concentrations in seawater. Spatial variation indicated the role of physicochemical properties on distribution of antibiotics in seawater and sediments. The results emphasize the need to pay attention to antibiotic contamination in water and sediments of the Persian Gulf.
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•6 antibiotics occur in Persian Gulf, Iran (water: 0.8-89 ng/L, sediments: 1–118 ng/g).•Winter- and summer-time content of 2 antibiotics was different in seawater (p ˂ 0.05).•Direct correlation was seen between antibiotics and pH, TOC, Mg and K in water.•Processes in WWTPs showed antibiotics cannot be fully removed (0.1–88%).•Pseudo-partitioning coefficient (kd,s) of antibiotics was obtained 88–28,436 L/kg.
The need for energy efficient Domestic Wastewater (DWW) treatment is increasing annually with population growth and expanding global energy demand. Anaerobic treatment of low strength DWW produces ...methane which can be used to as an energy product. Temperature sensitivity, low removal efficiencies (Chemical Oxygen Demand (COD), Suspended Solids (SS), and Nutrients), alkalinity demand, and potential greenhouse gas (GHG) emissions have limited its application to warmer climates. Although well designed anaerobic Membrane Bioreactors (AnMBRs) are able to effectively treat DWW at psychrophilic temperatures (10–30 °C), lower temperatures increase methane solubility leading to increased energy losses in the form of dissolved methane in the effluent. Estimates of dissolved methane losses are typically based on concentrations calculated using Henry's Law but advection limitations can lead to supersaturation of methane between 1.34 and 6.9 times equilibrium concentrations and 11–100% of generated methane being lost in the effluent. In well mixed systems such as AnMBRs which use biogas sparging to control membrane fouling, actual concentrations approach equilibrium values. Non-porous membranes have been used to recover up to 92.6% of dissolved methane and well suited for degassing effluents of Upflow Anaerobic Sludge Blanket (UASB) reactors which have considerable solids and organic contents and can cause pore wetting and clogging in microporous membrane modules. Microporous membranes can recover up to 98.9% of dissolved methane in AnMBR effluents which have low COD and SS concentrations. Sequential Down-flow Hanging Sponge (DHS) reactors have been used to recover between 57 and 88% of dissolved methane from Upflow Anaerobic Sludge Blanket (UASB) reactor effluent at concentrations of greater than 30% and oxidize the rest for a 99% removal of total dissolved methane. They can also remove 90% of suspended solids and COD in UASB effluents and produce a high quality effluent. In situ degassing can increase process stability, COD removal, biomass retention, and headspace methane concentrations. A model for estimating energy consumption associated with membrane-based dissolved methane recovery predicts that recovered dissolved and headspace methane may provide all the energy required for operation of an anaerobic system treating DWW at psychrophilic temperatures.
Primary fuel to unit operation energy conversion process. Display omitted
•Anaerobic systems can lose between 11 and 100% of generated methane in the effluent.•Membrane systems can recover up to 98.9% dissolved methane.•Microporous membranes may ares suitable for AnMBR effluent degassing.•Down Hanging Sponge reactors can efficiently recover dissolved methane and produce a high quality effluent.•Net-zero wastewater treatment may be achieved with dissolved methane recovery.
Because of its extremely low concentrations and strong resistance to most treatment technologies, perchlorate has become one of the biggest challenges currently being faced by the drinking water ...industry. Although significant research has been performed to evaluate different treatment technologies for perchlorate removal from drinking water, there has not been a holistic review performed recently. A complete and critical review on the intriguing contaminant ‘perchlorate’ is presented. The sources of perchlorate along with the degree of contamination are discussed. The policy aspects including the regulation and toxicity in addition to the most recent developments in perchlorate analysis are also considered. The applicable treatment technologies including their feasibility are discussed in detail. Although some technologies such as microbial reduction and ion-exchange have become more established than the others, there is still not a single technology that can be directly applied to a drinking water treatment system for compete removal of perchlorate. Although significant research is still being conducted to come up with a novel technology for perchlorate remediation, it is highly likely that it would not be a single novice or conventional technology but a combination of these technologies that would have to be employed to overcome this challenge.
This investigation was aimed to identify microplastics in the sediment and mudskipper fish (Periophthalmus waltoni) in mangrove forests in southern Iran. Sediments and mudskipper samples were ...collected at high, mid, and low tidal points of five stations. A total of 2657 plastic particles in different size, color, shape, and genera were identified from sediment samples and 15 microplastic were isolated from mudskippers. The highest and lowest abundance of isolated microplastics from sediments was observed in mangrove forests of Bidkhoun (urban area) and Bordkhon, respectively while no microplastics were found in the fish tissue in those stations. The black (60%) and white (7%) color microplastics in the mudskipper had the highest and the lowest frequency. The highest and lowest polymers in mangrove forest sediments were corresponded to polystyrene (26%) and polycarbonate (3%), respectively. Raman and Fourier transform infrared spectroscopy (FT-IR) techniques were used to identify the type of the polymer. Most of the microplastics found were made of polystyrene, polypropylene, and polyethylene terephthalate. The type of studied area and texture of sediment separately affected the frequency of microplastic and mesoplastic (P-value <0.05) in the sediment samples. The abundance of microplastics in the sediment samples of the Bidkhoun mangrove forest was higher than other studied stations due to proximity to urban and industrial areas. The findings of this study raised concerns about microplastic pollution in the mangrove forests of southern Iran, a threat to the ecosystem and public health, which requires careful actions to prevent and diminish its adverse effects.
•We studied microplastic in the sediment and mudskipper in Iranian mangrove forests.•Microplastic abundance was correlated to sediment tissue and pH.•Fiber-shaped and white particles were the most common microplastics in sediment.•PS, PP, and PET were dominant polymers in sediment and fish.•The sediment texture affected meso- and micro-plastics frequency (P-value <0.05).
In the current study, the influence of iron oxide nanoparticles and chitosan (CS) on the adsorption capacity of natural clay for chromium removal from aqueous media was explored. Clay-based ...adsorbents (clay, CS/Clay, Clay/Fe3O4, and CS/Clay/Fe3O4) were manufactured and their physicochemical properties were identified. The effects of operating factors on the adsorption efficiency were optimized. The results showed that the adsorption equilibrium data for the clay, CS/Clay, and Clay/Fe3O4 corresponds to the Langmuir model, while for the CS/Clay/Fe3O4 is consistent with the Freundlich model. The maximum adsorption capacity (qmax) of Cr(VI) using clay, CS/Clay, Clay/Fe3O4 and CS/Clay/Fe3O4 were 63.69 mg/g, 80.30 mg/g, 97.08 mg/g, and 117.64 mg/g, respectively. It was showed that the addition of chitosan and Fe3O4 magnetic nanoparticles to the clay increases its adsorption capacity. The values of ΔG° and ΔH° parameter for Cr adsorption using adsorbents were negative, indicating that the removal process is spontaneous and exothermic. The kinetic behavior obeyed the pseudo-second-order model. The chromium removal process using all the adsorbents had a two-step mechanism. The wastewater of a leather factory was effectively treated using clay based-adsorbents. Based on R2, MSE, SSE, and ARE values, good agreement was observed between the ANFIS model and experimental outcomes.
•Clay was composited with chitosan (CS) and Fe3O4 for Cr(VI) adsorption.•The maximum Cr-adsorption capacity onto CS/Clay/Fe3O4 was obtained 117.64 mg/g.•The adsorbent mass, Cr(VI) concentration, and pH affected the adsorption efficiency.•The adsorption process was followed pseudo second order kinetic model.•The ANFIS model was used to predict the Cr adsorption efficiency onto adsorbents.
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•Nano-scale adsorbent was produced from eggshell wastes.•Eggshell nano-particles were used as sorbent of Hg(II) and methyl violet dye.•Surface properties of nano-particles were fully ...determined (BET = 5.6 m2/g).•Sorption data was obeyed Freundlich and second-order kinetic model.•The landfill leachate and textile wastewater was treated by the sorbent.
A nano-scale sorbent was produced from eggshell wastes for sorption of Hg(II) and methyl violet (MV) from aqueous solutions and real wastewaters. The properties of the nano-particles were fully determined using SEM, DLS, FTIR, XRD, BET, TGA, AFM, EDAX, mapping, and TEM analyses. The adsorbent structure mainly contained carbonate and silica. The effects of influential parameters including temperature, contact time, initial contaminants concentration, sorbent dose, and initial pH on the removal efficiency were investigated. The maximum sorption efficiency of Hg(II) and MV occurred at pH of 6 and 9 and temperatures of 25 °C and 55 °C, respectively. Freundlich model could be interpreted the equilibrium data of the sorption process of both contaminants. The maximum sorption capacity of Hg(II) and MV using eggshell nano-particles was obtained as 116.27 mg/g and 123.45 mg/g, respectively. The dynamic behavior of the process was studied using two kinetic models. The sorption system performance was also examined and t1/2 were determined as 4.34 min for Hg(II) and 4.97 min for MV. The sorption process of Hg(II) and MV was exothermic and endothermic, respectively. Effective sorption after seven cycles and successful treatment of landfill leachate and textile wastewater with eggshell nano-particles confirms its adequacy.
To reduce environmental and human health risks of contaminated sites, having a comprehensive knowledge about the polycyclic aromatic hydrocarbon (PAH) removal processes is crucial. PAHs are ...contaminants which are highly recognized to pose threats to humans, animals, and plants. PAHs are hydrophobic and own two or more benzene rings, and hence are resistant to structural degradation. There are various techniques which have been developed to treat PAH-contaminated soil. Four distinct processes to remove PAHs in the contaminated soil, thought to be more effective techniques, are presented in this review: soil washing, chemical oxidation, electrokinetic, phytoremediation. In a surfactant-aided washing process, a removal rate of 90% was reported. Compost-amended phytoremediation treatment presented 58–99% removal of pyrene from the soil in 90 days. Chemical oxidation method was able to reach complete conversion for some PAHs. In electrokinetic treatment, researchers have achieved reliable results in removal of some specific PAHs. Researchers’ innovations in novel studies and advantages/disadvantages of the techniques are also investigated throughout the paper. Finally, it should be noted that an exclusive method or a combination of methods by themselves are not the key to be employed for remediation of every contaminated site but the field characteristics are also essential in selection of the most appropriate decontamination technique(s). The remedy for selection criteria is based on PAH concentrations, site characteristics, costs, shortcomings, and advantages.
The natural clay is an abundant, accessible, and low-cost material that has the potential for use in the water and wastewater industry. In this paper, Iranian natural clay and clay/Fe-Mn composite ...were used to remove toxic arsenic from the liquid environment. The natural clay and clay/Fe-Mn composite were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDX), X-ray diffractometry (XRD), thermo-gravimetric analysis (TGA), and atomic force microscopy (AFM) techniques. The effects of parameters (initial pH, temperature, sorption dose, and contact time) on the efficiency and behavior of the arsenic(V) adsorption process were studied. Freundlich (
R
2
= 0.945 and 0.989), Langmuir (
R
2
= 0.922 and 0.931), modified Langmuir (
R
2
= 0.921 and 0.929), and Dubinin–Radushkevich (
R
2
= 0.706 and 0.723) models were fitted to evaluate the equilibrium data of arsenic(V) adsorption process by natural clay and clay/Fe-Mn composite, respectively. The Langmuir adsorption capacity of arsenic(V) by the natural clay and clay/Fe-Mn composite was determined to be 86.86 mg/g and 120.70 mg/g, respectively. The arsenic(V) adsorption process followed the pseudo-second-order model. Negative values of Δ
G
° and Δ
H
° showed that the arsenic(V) sorption by the studied materials is thermodynamically spontaneous and exothermic. According to the findings, the natural clay and clay/Fe-Mn are suitable and recyclable sorbents for arsenic(V) adsorption from aqueous solutions. Also, the composite of clay with iron and manganese can improve the efficiency of clay in the removal of arsenic.
A beta type-chitin was produced from the shell of
Penaeuse semisulcatuse
shrimp for removal of lead and cadmium from the aqueous environment. Full physicochemical properties of the chitin (FTIR, SEM, ...mapping, XRD, EDX, AFM, and TGA-DTG) were obtained. Effects of solution pH, chitin dose, metals concentration, and contact time on the lead and cadmium adsorption were assessed. The solution pH had a great influence on the metal removal. Pseudo-first and pseudo-second order models were used to evaluate the kinetic behavior of metals adsorption by
P. semisulcatuse
chitin. Freundlich isotherm model was slightly better than the Langmuir model to describe the adsorption data. The R
L
value (obtained from the Langmuir model) for the adsorption of lead and cadmium was calculated to be 0.027 and 0.133, respectively, which showed the metals adsorption process by the chitin is desirable. The maximum adsorption capacity of lead and cadmium by
P. semisulcatuse
chitin was determined 13.14 mg/g and 19.15 mg/g, respectively. To desorb the adsorbed-metal from the chitin, the 1M HNO
3
solution was applied and the heavy metals desorption was suitable (90%). The half life (t
1/2
) factor in the adsorption of Pb and Cd onto chitin was calculated 2.817 min and 3.876 min, respectively.
