Use Of Powdered Activated Carbon Research Articles

Using zeolite filters to reduce activated carbon use in micropollutant removal from wastewater

Micropollutants (MPs) are a wide group of human-made chemicals, such as pharmaceuticals and/or industrial compounds, with a negative impact on ecosystems. As they are discharged through water lines, they are a common presence in wastewater treatment plants (WWTPs). Among the known MPs removal treatments, adsorption-based processes are mostly used given their high MP removal capacity, although their production costs and environmental impact can be high. This is the case of powdered activated carbon (PAC), that remains nevertheless often the best option. Therefore, the optimization of PAC adsorption through the combination with natural zeolites is an interesting perspective. In this study, a combined approach made of zeolite-based filter and PAC to reduce water concentrations of eleven micropollutants is reported. The addition of a zeolite-based removal step increased the overall average removal by 14 % compared to 55 % obtained by the sole PAC adsorption. The combined zeolite-PAC process, by having higher removal efficiency allows a reduction in the use of PAC with interesting potential savings in costs and CO2 emissions. Also, a zeolite step before conventional PAC can ease the organic matter loading on the carbon, allowing for an improved recirculation in the biology tank, and can make the use of renewable sources-based PAC more appealing.

Advanced hybrid membranes for efficient nickel retention from simulated wastewater

AbstractThis paper describes the preparation of a new type of hybrid material suitable to be used for the amendment of wastewaters laden with Ni ions relying on two purification principles, mechanical and adsorption. The membranes were prepared using as first component copolymers of acrylonitrile with vinyl acetate, acrylic acid or methacrylic acid. The second component of the developed membranes consisted of powdered activated carbon (PAC), of natural or synthetic origin, used in a content of either 4% or 8%. In this way, separation based on porosity is combined with the adsorptive properties of PAC. Hybrid membranes, prepared by phase inversion, were fully characterized by Fourier transform IR (FTIR) spectroscopy, pure water flux analysis, TGA, SEM, Brunauer–Emmett–Teller analysis and XRD. Moreover, water amendment was also investigated using synthetic water bearing heavy metals, in our case nickel, a laboratory electrodialysis set‐up being used for this purpose. FTIR revealed that the use of PAC led to several peaks at low wavelength (900–650 cm−1). Pure water flux values vary in a fairly wide range, from 0.02 to almost 1.00, depending on the preparation conditions. It can be concluded that the final properties of the developed membranes may be adjusted by changing either the copolymer or the PAC. An additional control is provided by the amount of PAC. The developed membranes were found to achieve an enhanced release of Ni ions, as the percentage of extraction was at least 51%. © 2021 Society of Chemical Industry

Powdered activated carbon (PAC) – vacuum-assisted air gap membrane distillation (V-AGMD) hybrid system to treat wastewater containing surfactants: Effect of operating conditions

Membrane distillation (MD), which uses hydrophobic porous membranes with a temperature gradient to produce pure water, has the potential to treat high-salinity wastewater. However, it cannot directly treat wastewater containing surfactants, which lower the surface tension and thus result in membrane wetting. To overcome this limitation, this study proposed a hybrid process consisting of powdered activated carbon (PAC) adsorption and MD, where PAC removes the surfactants in the wastewater to alleviate the wetting of the MD membranes. A bench-scale vacuum-assisted air gap MD (V-AGMD) equipment was adopted for the treatment of synthetic wastewater containing inorganic salts and surfactants. The conductivity of the permeate from V-AGMD was continuously monitored to detect membrane wetting. Without the use of PAC, the MD membrane was wetted within a short period, which decreased as the surfactant concentration increased. On the other hand, the addition of PAC retards the onset of wetting even at higher surfactant concentrations. The effectiveness of the PAC addition to the MD system on wetting control was examined under various conditions to elucidate its mechanism.

The influence of natural organic matter on the adsorption of microcystin-LR by powdered activated carbon

In this study, microcystin-LR (MC-LR) adsorption to four different types of powdered activated carbon (PAC) was evaluated to provide insight into the use of PAC to treat water containing MC-LR.

Mercury Reduction—The Plant Experience

This paper communicates the design and installation process of a mercury capture system in a cement kiln located in the state of Oregon. This paper will document the timeline and decision points between 2006 and 2012 pertinent to the reduction of mercury, first to meet a state agreement and later to meet new federal government requirements. The use of powder-activated carbon as a collection medium will be discussed, along with various materials tested with less positive results. The optimization of the system to increase performance will be covered, along with methods of mercury measurement and tracking employed for reporting. This paper will show that the subject cement plant overcame a significant challenge to install a system capable of bringing emissions in compliance with the Environmental Protection Agency Portland Cement National Emissions Standard for Hazardous Air Pollutants limit.

Environmental Comparison of Biochar and Activated Carbon for Tertiary Wastewater Treatment.

Micropollutants in wastewater present environmental and human health challenges. Powdered activated carbon (PAC) can effectively remove organic micropollutants, but PAC production is energy intensive and expensive. Biochar adsorbents can cost less and sequester carbon; however, net benefits depend on biochar production conditions and treatment capabilities. Here, life cycle assessment was used to compare 10 environmental impacts from the production and use of wood biochar, biosolids biochar, and coal-derived PAC to remove sulfamethoxazole from wastewater. Moderate capacity wood biochar had environmental benefits in four categories (smog, global warming, respiratory effects, noncarcinogenics) linked to energy recovery and carbon sequestration, and environmental impacts worse than PAC in two categories (eutrophication, carcinogenics). Low capacity wood biochar had even larger benefits for global warming, respiratory effects, and noncarcinogenics, but exhibited worse impacts than PAC in five categories due to larger biochar dose requirements to reach the treatment objective. Biosolids biochar had the worst relative environmental performance due to energy use for biosolids drying and the need for supplemental adsorbent. Overall, moderate capacity wood biochar is an environmentally superior alternative to coal-based PAC for micropollutant removal from wastewater, and its use can offset a wastewater facility's carbon footprint.

Removal of micropollutants in municipal wastewater treatment plants by powder-activated carbon

Micropollutants (MP) are only partly removed from municipal wastewater by nutrient removal plants and are seen increasingly as a threat to aquatic ecosystems and to the safety of drinking water resources. The addition of powder activated carbon (PAC) is a promising technology to complement municipal nutrient removal plants in order to achieve a significant reduction of MPs and ecotoxicity in receiving waters. This paper presents the salient outcomes of pilot- and full-scale applications of PAC addition in different flow schemes for micropollutant removal in municipal wastewater treatment plants (WWTPs). The sorption efficiency of PAC is reduced with increasing dissolved organic carbon (DOC). Adequate treatment of secondary effluent with 5-10 g DOC m(-3) requires 10-20 g PAC m(-3) of effluent. Counter-current use of PAC by recycling waste PAC from post-treatment in a contact tank with an additional clarifier to the biology tank improved the overall MP removal by 10 to 50% compared with effluent PAC application alone. A dosage of 15 g PAC m(-3) to a full-scale flocculation sand filtration system and recycling the backwash water to the biology tank showed similar MP elimination. Due to an adequate mixing regime and the addition of adapted flocculants, a good retention of the fine fraction of the PAC in the deep-bed filter were observed (1-3 g TSS m(-3); TSS: total suspended solids). With double use of PAC, only half of the PAC was required to reach MP removal efficiencies similar to the direct single dosage of PAC to the biology tank. Overall, the application of PAC in WWTPs seems to be an adequate and feasible technology for efficient MP elimination (>80%) from wastewater comparable with post ozonation.

Integration of ceramic membrane microfiltration with powdered activated carbon for advanced treatment of oil-in-water emulsion

An integration process of ceramic membrane microfiltration (MF) with powdered activated carbon (PAC) was used to treat the oil-in-water emulsion in order to enhance the treatment efficiency. The role of PAC addition in flux enhancement mechanisms was investigated in detail. Results showed that the membrane flux for this system with particles was obviously higher than that of the oil-in-water emulsion alone. Combined with FESEM and EDS analyses, it was concluded that the gel layer formed on the membrane surface could be obviously reduced due to the mechanical scouring effect of particles according to the estimation of hydrodynamic forces, resulting in a higher membrane flux. The addition of PAC had no obvious effect on the removal efficiency of TOC and p-xylene, and they were removed about 96% in all cases. In short, the results of the present study demonstrated that the use of PAC as an additive in the integrated MF-PAC system was effective to mitigate membrane fouling and as a result increased the membrane flux because of scouring action.

Mechanism and kinetic considerations of TOC removal from the powdered activated carbon ozonation of diclofenac aqueous solutions

Ozonation of DCF in aqueous solution in the presence of powdered activated carbon (PAC) has been studied for mechanistic and kinetic purposes. The effects of gas flow rate, ozone gas concentration and initial TOC on the TOC elimination rate were then investigated. The use of PAC allows liquid–solid and internal diffusion mass transfer resistances being eliminated. Gas–liquid mass transfer resistance is also eliminated when ozonation is applied to DCF preozonated solutions. In the absence of mass transfer resistances a mechanism of reactions involving homogeneous and heterogeneous steps for TOC removal was proposed. From this mechanism a mathematical model constituted by mass balances of main species in water was established. Considerations about the changing nature of ozonation intermediates, as being promoters or inhibitors of ozone decomposition, is a key point to better predict the experimental concentrations of species present in this system.

Photocatalytic hybrid system in degradation of herbicide (metsulfuron–methyl)

Photocatalytic oxidation is becoming an emerging technology in water and wastewater treatment. Photocatalysis often leads to complete degradation of organic pollutants without any need for chemicals. In this study, the removal of the herbicide metsulfuron–methyl (MM) by photocatalysis was studied. Titanium dioxide (TiO2) was used as a catalyst in a UV reactor equipped with three lamps each with 8 watts of power. The total surface of UV lamps was 537 cm2. The capacity of the photocatalytic reactor was 1.5 L. The effects of parameters such as pH and TiO2 dose on the removal of MM were studied. The combined system of the photocatalytic reactor with powder activated carbon (PAC) adsorption was also investigated. The results indicate that the use of PAC reduced the TiO2 dose and led to very high removal efficiency. A very small dose of 0.05 g/L PAC reduced TiO2 requirement from 2 g/L to less than 0.5 g/L. A detailed molecular size distribution measurement made using high performance size exclusion chromatography (HPSEC) showed that TiO2 can degrade the MM to a small molecular weight compound of 50 daltons within a detention time of 40 minutes. This hybrid system was found to be technically and economically more efficient than the other processes used to remove herbicides and pesticides.

Rapid adsorption pretreatment with submicrometre powdered activated carbon particles before microfiltration

Manufacturer-supplied powdered activated carbon (PAC) was ground to produce submicrometre particles (0.8 and 0.6 m median diameter) for use as an adsorbent before microfiltration (MF) for drinking water treatment. Batch tests revealed that the microground PAC adsorbed natural organic matter (NOM) much more rapidly and had a higher adsorptive capacity than ordinary PAC. The water samples pretreated with the submicrometre PAC were subjected to MF, and the results of experiments with different PAC contact times revealed that a 1 min retention time was sufficient for adsorptive removal of NOM. The use of submicrometre PAC permitted not only shorter PAC contact times but also a 75% reduction in dose.

Application of a PAC-Membrane Hybrid System for Removal of Organics from Secondary Sewage Effluent: Experiments and Modelling

As world supplies of clean, fresh water come under increasing pressure and the need for water reuse rises, membrane technology is becoming increasingly important as a possible solution. However, membrane fouling is a major obstacle to the successful operation of the membrane process in wastewater treatment. In this study, a submerged hollow-fiber membrane with powdered activated carbon (PAC) adsorption was investigated for the removal of organics from secondary sewage effluent from a sewage treatment plant. The use of PAC in the membrane system was found to be very effective, not only in removing refractory organics, but also in reducing membrane clogging. A simple mathematical model was developed to predict the effluent quality [in terms of total organic carbon (TOC)] of the submerged membrane–adsorption hybrid system.

Synergistic effects of potassium permanganate and PAC in direct filtration systems for THM precursor removal

Some traditional methods for reducing trihalomethane concentrations in finished water may be less effective or inappropriate for direct filtration water treatment systems. Reduced prefiltration hydraulic detention times and mass solid loading considerations affect the use of potassium permanganate (KMnO 4) and powdered activated carbon (PAC) in direct filtration systems. KMnO 4 and PAC were investigated both individually and in combination to determine the effectiveness in reducing maximum total trihalomethane potential (MTP). The effectiveness of the chemicals was evaluated by using jar tests and/or a 23,850 l d −1 direct filtration pilot plant. The results indicated that permanganate oxidation of THM precursors to reduce MTP was ineffective at low concentrations (< 1 mg l −1) and prefiltration contact times (< 1 h) typical of direct filtration systems. PAC (30 mg l −1) adsorption of THM precursors reduced MTP by 10–26%, however, the time of pilot filter run length was reduced by 40%. Combined use of permanganate (2 mg l −1) and PAC allowed effective control of excess residual permanganate ion and exhibited a synergistic effect by reducing MTP up to 35%, which was a greater reduction than achieved by either compound individually.