Powdered Activated Carbon Addition Research Articles

Operational mode and powdered activated carbon promoting syntrophic propionate oxidation during anaerobic digestion of complex organic substances

Operational mode and powdered activated carbon (PAC) are key factors facilitating microbial syntrophy and interspecies electron transfer during anaerobic digestion, consequently benefiting process stability and efficient methanogenesis. In this study, continuous-flow reactor (CFR) and sequencing batch reactor (SBR), with and without the addition of PAC, respectively, were operated to examine their effects on system performance and methanogenic activity. Based on the cycle-test result, the PAC-amended CFR (CFRPAC) recorded both the highest methane yield (690.1 mL/L) and the maximum CH4 production rate (28.8 mL/(L·h)), while SBRs exhibited slow methanogenic rates. However, activity assays indicated that SBRs were beneficial for organics removal in batch experiments fed with peptone. Taxonomic and functional analysis confirmed that CFRs were optimal for proliferating oligotrophs (e.g., Geobacter) and SBRs were more suitable for copiotrophs (e.g., Desulfobulbus). Metagenomic analysis revealed that CFRs had efficient acetate metabolic pathways from propionate and ethanol, whereas SBRs did not, resulting in the buildup of propionate. Furthermore, Methanobacterium and Methanothrix were acclimated to the different operational conditions, while acetoclastic Methanosarcina and hydrogenotrophic Methanolinea were acclimated in SBRs (5.1–13.4%) and CFRs (0.3–1.7%), respectively. This study confirmed the enhancement of microbial syntrophy by the addition of PAC as well as the acclimation of electroactive bacteria (e.g., Geobacter) with complex organic substances.

A thorough analysis of the occurrence, removal and environmental risks of organic micropollutants in a full-scale hybrid membrane bioreactor fed by hospital wastewater

The Urban Wastewater Treatment Directive recent draft issued last October 2022 pays attention to contaminants of emerging concern including organic micropollutants (OMPs) and requires the removal of some of them at large urban wastewater treatment plants (WWTPs) calling for their upgrading. Many investigations to date have reported the occurrence of a vast group of OMPs in the influent and many technologies have been tested for their removal at a lab- or pilot-scale. Moreover, it is well-known that hospital wastewater (HWW) contains specific OMPs at high concentration and therefore its management and treatment deserves attention. In this study, a 1-year investigation was carried out at a full-scale membrane bioreactor (MBR) treating mainly HWW. To promote the removal of OMPs, powdered activated carbon (PAC) was added to the bioreactor at 0.1 g/L and 0.2 g/L which resulted in the MBR operating as a hybrid MBR. Its performance was tested for 232 target and 90 non-target OMPs, analyzed by UHPLC-QTOF-MS using a direct injection method. A new methodology was defined to select the key compounds in order to evaluate the performance of the treatments. It was based on their frequency, occurrence, persistence to removal, bioaccumulation and toxicity. Finally, an environmental risk assessment of the OMP residues was conducted by means of the risk quotient approach. The results indicate that PAC addition increased the removal of most of the key OMPs (e.g., sulfamethoxazole, diclofenac, lidocaine) and OMP classes (e.g., antibiotics, psychiatric drugs and stimulants) with the highest loads in the WWTP influent. The hybrid MBR also reduced the risk in the receiving water as the PAC dosage increased mainly for spiramycin, lorazepam, oleandomycin. Finally, uncertainties and issues related to the investigation being carried out at full-scale under real conditions are discussed.

Deciphering anaerobic ethanol metabolic pathways shaped by operational modes

Efficient anaerobic digestion requires the syntrophic cooperation among diverse microorganisms with various metabolic pathways. In this study, two operational modes, i.e., the sequencing batch reactor (SBR) and the continuous-flow reactor (CFR), were adopted in ethanol-fed systems with or without the supplement of powdered activated carbon (PAC) to examine their effects on ethanol metabolic pathways. Notably, the operational mode of SBR and the presence of CO2 facilitated ethanol metabolism towards propionate production. This was further evidenced by the dominance of Desulfobulbus, and the increased relative abundances of enzymes (EC: 1.2.7.1 and 1.2.7.11) involved in CO2 metabolism in SBRs. Moreover, SBRs exhibited superior biomass-based rates of ethanol degradation and methanogenesis, surpassing those in CFRs by 53.1% and 22.3%, respectively. Remarkably, CFRs with the extended solids retention time enriched high relative abundances of Geobacter of 71.7% and 70.4% under conditions with and without the addition of PAC, respectively. Although both long-term and short-term PAC additions led to the increased sludge conductivity and a reduced methanogenic lag phase, only the long-term PAC addition resulted in enhanced rates of ethanol degradation and propionate production/degradation. The strategies by adjusting operational mode and PAC addition could be adopted for modulating the anaerobic ethanol metabolic pathway and enriching Geobacter.

Evaluating Biogas Production of Polylactic acid with the addition of Conductive Materials

Objectives:The demand for polylactic acid (PLA) is increasing as an alternative to conventional petroleum-based plastics due to its eco-friendly characteristics. PLA can be processed through anaerobic digestion (AD) along with other organic wastes to promote efficient and controlled biodegradation. This study aimed to evaluate the feasibility of biogas production through AD of PLA and to enhance efficiency through the addition of conductive materials.Methods:Two sets of biochemical methane potential (BMP) tests were conducted. The first BMP test involved substrate/inoculum ratios (SIRs) of 0.6, 0.8, 1.0, 1.2, 1.4, and 1.6 (g COD PLA/g COD seed sludge). Conductive materials powdered activated carbon (PAC), carbon nanotube (CNT), and Magnetite were individually added to reactors at a concentration of 3 g/L in the second test.Results and Discussion:The study revealed an increasing trend in methane production and methane yield with higher levels of PLA input. However, a decline in methane yield was observed when PLA was injected at levels surpassing 35g COD/L. This phenomenon can be attributed to a prolonged Lag phase, indicating a longer adaptation period for microorganisms, consequently resulting in a reduction of the conversion rate from 1g COD substrate to methane. The introduction of conductive material led to elevated cumulative methane production and methane yield in comparison to the control group. Notably, Magnetite exhibited the highest increase rate among the tested materials. Additionally, the addition of PAC demonstrated favorable results in terms of methane production rate at 99.4mL/L/Day and a Lag phase of 5.7 days. Conclusion:Experiments were conducted to evaluate the effects of PLA biogas production and the injection of PAC, CNT, and Magnetite at various substrate/inoculum ratios. When PLA was used as a substrate for anaerobic digestion, its feasibility was confirmed. However, it exhibited lower efficiency compared to other substrates. Therefore, the addition of a conductive material was found to increase the biogas production efficiency.

Enhanced production of biohydrogen and biomethane through a two-stage anaerobic fermentation of food waste mixed with conductive additives

This study was conducted to examine the effects of three different conductive materials (CMs) on H2 and CH4 production in a two-stage fermentation process (TSFP). This study also investigated the distinct roles played by the different types of CMs within the process. The study findings revealed that the combination of two or more CMs led to a significant improvement in production compared to using a single CM. Magnetite nanoparticle (MNP) played a crucial role in enhancing H2 productivity during the first stage of the TSFP. The TSFP with carbon nanotubes (CNT) + MNP demonstrated the highest H2 yield of 121 ± 7 mL/g·COD with the H2 production rate of 219 ± 18 mL/hr, followed by the TSFP with MNP alone yielded the second highest H2 of 81 ± 5 mL/g·COD with the H2 production rate of 169 ± 25 mL/hr. Both powdered activated carbon (PAC) alone (277 ± 17 mL/g·COD) and PAC + CNT (278 ± 15 mL/g·COD) showed the highest CH4 yield, indicating that PAC contributed to higher CH4 production in the second stage of the TSFP. The addition of PAC to the samples led to higher chemical oxygen demand (COD) removal efficiency in the TSFP, while the presence of MNP significantly increased the total energy production.

Adsorption of lead ions by activated carbon doped sodium alginate/sodium polyacrylate hydrogel beads and their in-situ recycle as sustainable photocatalysts

In this study, sodium alginate (SA), sodium polyacrylate (PAAS) and powdered activated carbon (PAC) were cross-linked by calcium ions [(Ca(II)] to form SA/PAAS/PAC (SPP) hydrogel beads. The hydrogel-lead sulfide (SPP-PbS) nanocomposites were successfully synthesized by in-situ vulcanization after the lead ions [(Pb(II)] adsorption. SPP showed an optimal swelling ratio (600% at the pH value of 5.0) and superior thermal stability (206 °C of heat-resistance index). The adsorption data of Pb(II) was compatible with the Langmuir model, and the maximum adsorption capacity of SPP was 391.65 mg/g after optimizing the mass ratio of SA to PAAS (3:1). The addition of PAC not only enhanced the adsorption capacity and stability, but also promoted photodegradation. The significant dispersive capacity of PAC and PAAS resulted in PbS nanoparticles with particle sizes of around 20 nm. SPP-PbS showed good photocatalysis and reusability. The degradation rate of RhB (200 mL, 10 mg/L) was 94% within 2 h and maintained above 80% after 5 cycles. The treatment efficiency of SPP was more than 80% in actual surface water. The results of quenching experiments and electron spin resonance (ESR) experiments revealed that the superoxide radicals (O2–) and holes (h+) were the main active species in the photocatalytic process.

Optimization and Modelling the Mechanical Performance of Date Palm Fiber-Reinforced Concrete Incorporating Powdered Activation Carbon Using Response Surface Methodology.

Date palm fiber (DPF) has been reported to have many advantages when used in concrete, however, its major disadvantage is that it causes a reduction in compressive strength. In this research, powdered activated carbon (PAC) was added to cement in the DPF-reinforced concrete (DPFRC) to lessen the loss in strength. PAC has not been properly utilized as an additive in fiber reinforced concrete even though it has been reported to enhance the properties of cementitious composites. Response surface methodology (RSM) has also been utilized for experimental design, model development, results analysis, and optimization. The variables were DPF and PAC as additions each at proportions of 0%, 1%, 2%, and 3% by weight of cement. Slump, fresh density, mechanical strengths, and water absorption were the responses that were considered. From the results, both DPF and PAC decreased the workability of the concrete. DPF addition improved the splitting tensile and flexural strengths and reduced the compressive strength, and up to 2 wt% PAC addition enhanced the concrete's strength and lowered the water absorption. The proposed models using RSM were extremely significant and have excellent predictive power for the concrete's aforementioned properties. Each of the models was further validated experimentally and was found to have an average error of less than 5.5%. According to the results of the optimization, the optimal mix of 0.93 wt% DPF and 0.37 wt% PAC as cement additives resulted in the best properties of the DPFRC in terms of workability, strength, and water absorption. The optimization's outcome received a 91% desirability rating. The addition of 1% PAC increased the 28-day compressive strength of the DPFRC containing 0%, 1% and 2% DPF by 9.67%, 11.13% and 5.5% respectively. Similarly, 1% PAC addition enhanced the 28-day split tensile strength of the DPFRC containing 0%, 1% and 2% by 8.54%, 11.08% and 19.3% respectively. Likewise, the 28-day flexural strength of DPFRC containing 0%, 1%, 2% and 3% improved by 8.3%, 11.15%, 18.7% and 6.73% respectively with the addition of 1% PAC. Lastly, 1% PAC addition led to a reduction in the water absorption of DPFRC containing 0% and 1% DPF by 17.93% and 12.2% respectively.

Modeling and Optimization of Date Palm Fiber Reinforced Concrete Modified with Powdered Activated Carbon under Elevated Temperature

Date palm fiber (DPF) is one of the abundant solid waste materials in the agriculture sector in Saudi Arabia, and it is gaining great attraction due to its advantages compared to synthetic and other natural fibers. For proper utilization of DPF in cementitious composites, its performance under high temperatures needs to be understood. This is because DPF is a cellulose-based agricultural fiber material and is expected to degrade when subjected to high temperatures. This will cause a significant loss in strength and structural integrity of the composites. The use of Pozzolanic materials has been reported to reduce the loss in mechanical properties of cementitious composites under high temperatures. With powdered activated carbon (PAC) being a low-cost material compared to other Pozzolanic materials, this study utilized PAC as an additive to the DPF-reinforced concrete to mitigate its loss in mechanical strength when exposed to elevated temperature. The experiment was designed using response surface methodology (RSM), which was used to construct mathematical models for estimating the strengths of the concrete exposed to high temperatures. The DPF was added at proportions of 1%, 2%, and 3% by weight of cement. Similarly, the PAC was added at 1%, 2%, and 3% by weight of cement to the concrete. The concrete was subjected to elevated temperatures of 300 °C, 600 °C, and 900 °C for a 2 h exposure period. The degradation of the concrete in terms of mass loss and the compressive strength of the concrete after heating were measured. DPF in the concrete led to an escalation in weight loss and reduction in strength, which was more pronounced at a temperature of 600 °C and above. The addition of PAC resulted in an enhancement in the strengths of the concrete containing up to 2% DPF at 300 °C, while at 600 °C the improvement was minimal. The models developed for predicting the mass loss and strengths of the DPF-reinforced concrete under high temperatures were statistically significant with a high correlation degree. Based on the optimization results, DPF-reinforced concrete produced with 1% DPF, and 2.27% PAC as additives and subjected to a temperature of 300 °C for 2 h yielded the lowest mass loss of 2.05%, highest residual compressive strength and relative strength of 45.85 MPa and 106.7% respectively.

Effects of powdered activated carbon dosage on the performance of membrane bioreactors treating biochemical tail water

As a promising treatment technology for wastewater, the promotion of membrane bioreactors (MBR) is restricted by biological fouling. Among the measures used to mitigate membrane fouling, the addition of powdered activated carbon (PAC) to MBRs has been recognized as an effective practice. However, the effects of PAC dosage on the performance of MBRs that treat highly biochemical influent from wastewater treatment plants remain unclear. In this study, by investigating the treatment of biochemical tailwater by PAC–MBRs, we thoroughly analyzed the effects of PAC dosage on the contamination removal efficiency, membrane operation cycles, sludge mixture properties, and microorganism distributions. The results indicated that the addition of PAC enhanced the removal efficiency of MBRs depending on the contaminant of interest. For example, the removal efficiency of total nitrogen can be boosted from 30 % to 60 % with PAC addition, while the removal efficiencies of total phosphorus were comparable with or without PAC addition. Furthermore, the application of PAC in MBRs can prolong the duration of membranes by suppressing biological fouling. This was supported by the decreased microbial products, reduced smaller solid particles, and stronger stability of sludge particles. PAC addition also boosts the proportion of Proteus and decreases the proportion of Bacteroides, which helps to improve the removal efficiencies of contaminants. Finally, among the PAC dosages tested in our study, 1.5 g/L PAC was proposed as the optimal candidate for treating highly biochemical influents. For example, the corresponding time for transmembrane pressure to reach 0.03 MPa was 19 d at 1.5 g/L PAC, while these periods were 7 and 14 d at dosages of 0 and 0.5 g/L, respectively. Overall, the findings of this study will aid in the selection of optimal dosages for other systems with different types of influents.

Influence of powdered activated carbon on gravity-driven ultrafiltration for decentralized drinking water treatment: Insights from microbial community and biofilm structure

Gravity-driven membrane (GDM) filtration, an appealing approach for decentralized drinking water treatment, tolerates the development of membrane biofilms for the benefit of low energy consumption and stable flux. In this study, the effect of introducing powdered activated carbon (PAC) on the biofilm generated during long-term GDM filtration was investigated. The results indicated that the addition of PAC significantly enhanced the removal of dissolved organic compounds (DOC) (31 %), whereas only 15.7 % removal was achieved in the control GDM system without PAC. The improved permeate quality was attributed to the combined effects of adsorption and biodegradation of organic compounds by PAC. However, the presence of PAC reduced the permeability of the GDM system by 39 % compared to the control one, which was related to the synergetic effect of the increased extracellular polymeric substances (EPS) content and the decreased metazoan amounts (especially Nematoda) in the biofilm. A large number of substrates adsorbed by PAC facilitated the growth of bacteria and hence intensified the secretion of EPS. Meanwhile, the deposition of PAC on the membrane surface limited the movement space of metazoans, leading to a denser and flatter biofilm basal structure. Furthermore, fewer metazoans meant less predation on bacteria, which also contributed to bacterial reproduction. In addition, an enhanced removal efficiency of ammonia nitrogen was observed in the PAC/GDM system, corresponding to a much higher abundance of Nitrospira in bacterial community. This study links microbial community to hydraulic resistance of biofilm and has practical implications for the application of GDM processes.

Effect of two sorbents on the distribution and transformation of N-ethyl perfluorooctane sulfonamido acetic acid (N-EtFOSAA) in soil-soybean systems

The broad application of perfluoroalkyl acid (PFAA) precursors has led to their occurrence in soil, resulting in potential uptake and bioaccumulation in plants. In this study, we investigated the effect of powdered activated carbon (PAC) and montmorillonite on the distribution and transformation of a perfluorooctanesulfonic acid (PFOS) precursor, N-ethyl perfluorooctane sulfonamido acetic acid (N-EtFOSAA), in soil-plant systems. The results showed that N-EtFOSAA at 300 μg/kg was taken up by soybean roots and shoots together with its transformation products (i.e., perfluorooctane sulfonamide (PFOSA), PFOS), while decreasing the biomass of shoots and roots by 47.63% and 61.16%, respectively. PAC amendment significantly reduced the water leachable and methanol extractable N-EtFOSAA and its transformation products in soil. In the presence of soybean and after 60 days, 73.5% of the initially spiked N-EtFOSAA became non-extractable bound residues. Compared to the spiked controls, the PAC addition also decreased the total plant uptake of N-EtFOSAA by 94.96%. In contrast, montmorillonite showed limited stabilization performance for N-EtFOSAA and its transformation products and was ineffective to lower their bioavailability. Overall, the combination of PAC and soybean was found to be effective in immobilizing N-EtFOSAA in soil.

Study on Treatment of Tiny Pollution Water with PAC-HUM System in Kuitun River

Kuitun city, Xinjiang is dry and short of water, so it is urgent to treat and utilize all kinds of unconventional water. In view of this problem, we conducted a study on the treatment of tiny pollution water in Kuitun River. We investigated the effect of dosage of powder activated carbon (PAC) on hollow-fiber ultrafiltration membrane (HUM) performance. The results show that the stable operation time of hollow fiber ultrafiltration membranes lengthened and the rate of reduction of the flux was reduced when the PAC dosage was increased. The addition of PAC had no obvious effect on the resistance of membrane filtration. We conducted experiments to evaluate the effect of ultrafiltration of tiny pollution water in combination with PAC. When the parameters of operation and PAC dosage were appropriately regulated, the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and ferric ions (Fe) reached 62%, 32% and 90%, respectively. When the PAC dosage was 200 mg/L, 100 mg/L and 150 mg/L, the highest removal rates were achieved under normal temperature and pressure. The effluent COD was less than 5.0 mg/L, NH3-N was less than 1.5 mg/L and Fe was less than 0.5 mg/L, achieving better results than the quality standard of surface water (GB3838-2002). The treated water can be discharged into the river or recirculated to utilities. The fouled membrane was cleaned by water rinsing, water/acid rinsing and water/alkali rinsing, with recovery ratios of 44%, 81% and 88%, respectively. The results of this study can serve as a foundation for the efficient utilization of water resources and the development of new water treatment technologies in Xinjiang.

Removal of algae and algogenic odor compounds via combined pre-chlorination and powdered activated carbon adsorption for source water pretreatment

This study investigated the combination sequence and time interval of chlorination and powdered activated carbon (PAC) adsorption for the control of algae inactivation, algogenic odor removal, and disinfection by-product (DBP) formation. Results indicated that pre-chlorination/post-PAC exhibited the highest algae removal efficiency in all sequential combinations of PAC adsorption and chlorination, while it had displayed slight effect on the removal of DBPs. The evaluated sequential combinations all had significant effect on the removal of odor. Nevertheless, prolonged time interval between chlorination and PAC adsorption exhibited enhanced control of algae and odor compounds in all experiments; with increasing time interval from 0 to 15 min in pre-chlorination/post-PAC process, the removal efficiency of Chl-a, algal cell viability, GSM, and 2-MIB increased by 46%, 15%, 15% and 23%, respectively. In the combined processes, the odor removal efficiency was positively correlated with PAC dosage but negatively correlated with chlorine dosage. Furthermore, PAC addition could effectively reduce the total DBP yields, especially the N-DBPs. This study can provide a better understanding of improving in-situ operation of the pre-chlorination and PAC dosing systems for source water pretreatment.

Performance of a hybrid process integrating PAC adsorption with ceramic membrane ultrafiltration for drinking water treatment

Membrane separation technologies have broad application prospects in water treatment. Compared with polymeric membranes, ceramic membranes have higher stability for long-term operation in practical applications. Coupling ceramic membranes with other water treatment processes is an effective way to improve membrane treatment effect and alleviate membrane fouling. This study evaluated the water purification efficiency and membrane fouling behaviors of powdered activated carbon (PAC), flat-sheet ceramic membranes and their hybrid process in treating model organic pollutants and natural water. Results showed that the PAC-ceramic membrane hybrid process could alleviate the membrane fouling caused by humic acid but aggravate that caused by sodium alginate. Addition of PAC notably improved the removal performance of the ceramic membrane for organic matters in natural water as well as pharmaceutical and personal care products, and effectively controlled membrane fouling. The PAC adsorption obviously reduced the irreversible fouling of the ceramic membrane under multi-cycle operation. This study can provide a reference for the practical application of ceramic membranes in drinking water treatment.

Mechanism of powdered activated carbon enhancing caproate production

Caproate, produced by microbial chain elongation process, is potential to replace the diversified fossil-based products, contributing to carbon neutrality. However, its production performance is far from industrial application, so the cost-effective enhancement measures are highly needed. This study confirmed powdered activated carbon (PAC) has a significant effect on enhancing caproate production performance. The production, yield, and selectivity of caproate were improved by more than 1-fold by the optimized PAC dosage of 15 g/L, comparing with control. Mechanism investigation from a new visual angle showed that PAC accelerated ethanol oxidation to generate acetyl-CoA, and simultaneously boosted the efficiency of reverse β oxidation (RBO) by promoting the timely reaction of butyrate and acetyl-CoA to synthesis caproate. The addition of PAC also shifted the microbial community by enriching more caproate-producing bacteria but eliminating irrelevant ones. Furthermore, metagenomic analysis revealed that PAC effectively up-regulated the functional genes encoding key enzymes responsible for ethanol oxidation and RBO pathway, which was the root cause for the improved caproate production. This study presented the intrinsic insights into the mechanism of PAC promoting caproate generation, laying a foundation to the scale production of caproate.

Powdered activated carbon full-scale addition to the activated sludge reactor of a municipal wastewater treatment plant: Pharmaceutical compounds control and overall impact on the process

Powdered activated carbon (PAC) dosing to a conventional activated sludge (AS) reactor is a low-investment option for controlling pharmaceutical compounds (PhCs) in municipal wastewater treatment, but its advantages and limitations in real operating environments are not fully assessed. A 3-week PAC-AS full-scale test was conducted in an oxidation ditch plant to assess PAC impact on effluent quality (PhCs, dissolved organic carbon (DOC) and other parameters), energy consumption, sludge production and costs. DOC-normalized PAC doses of 0.7–2.6 mgPAC/mgDOC significantly reduced recalcitrant PhC discharge (e.g. by 63–83 % for carbamazepine and 67–69 % for diclofenac), the higher dose yielding a more reliable effluent quality. Effluent quality for total phosphorus, colour, organic matter and transmittance was also enhanced and no interference with nitrification, oxidation-reduction potential or dissolved oxygen in the oxidation ditch was observed, resulting in no energy consumption increase. PAC had no impact on effluent turbidity and mixed liquor suspended solids settleability, showing a positive effect on dewatered sludge dry weight and ultimately a 7–9 % increase on final sludge production. After stopping PAC dosing, PAC remaining in the return sludge presented adsorption capacity for some PhCs until it was completely out of the system. Estimated costs for PAC addition to AS-reactor compare favourably with literature data for PAC and GAC post-treatment and similarly with post-ozonation.

Mitigation of membrane fouling of alginate with combined actions of aeration and powdered activated carbon: Fouling behaviors and mechanisms.

A laboratory-scale flat-sheet ceramic microfiltration membrane system was developed to investigate the membrane fouling behaviors and mechanisms of sodium alginate (SA) in the presence of aeration and powdered activated carbon (PAC). When the SA concentration increased from 20 to 500 mg/L, the permeate flux decreased by 81.7%, and the transmembrane pressure (TMP) and resistance increased 1.7 and 24.5 times, respectively. At an SA concentration of 500 mg/L, it was found that the membrane fouling tended to decrease with the increase in the aeration rate, indicating high control of the fouling by air scouring, while PAC-aeration scouring produced a significant improvement in the permeate flux with substantially reduced fouling. In the microfiltration of 500 mg/L SA at an air flow rate of 2.2 L/min and PAC concentrations of 40, 100, and 250 mg/L, the flux increased by 179.3%, 238.0%, and 302.7%, the TMP decreased by 32.6%, 34.8%, and 45.7%, and the cake and pore blocking resistance decreased by 78.0%, 85.1%, and 87.9%, respectively, compared to the corresponding values without PAC-aeration scouring. Intermediate blocking and complete blocking models were confirmed to elucidate the effect of aeration scouring and PAC-aeration scouring on the mitigation of membrane fouling by SA. PRACTITIONER POINTS: Air scouring was effective at mitigating membrane fouling of sodium alginate. The addition of PAC could alleviate membrane fouling of SA. Synergistic scouring by aeration and PAC offers a promising means for more-efficient and cost-effective control of membrane fouling. The fouling mechanisms in various scenarios were elucidated.

Simultaneous coupling of fluidized granular activated carbon (GAC) and powdered activated carbon (PAC) with ultrafiltration process: A promising synergistic alternative for water treatment

Ultrafiltration (UF) has been extensively employed in current water treatment practice, during which limited removal for soluble contaminants and membrane fouling remain two perennial hurdles to efficient operation. This study proposed a promising approach by simultaneous coupling of fluidized granular activated carbon (GAC) and PAC with UF process, whereby PAC was responsible for improving effluent quality, and fluidized GAC was targeted for mitigating UF fouling and PAC deposition. The operational performance of such integrated GAC-PAC-UF system was systemically evaluated in a lab-scale setup. The results showed that fluidized GAC particles with larger size appeared highly effective in removing PAC deposition and fouling formed by surface water. PAC addition improved the effluent quality mainly by adsorbing humic acid-like substances. More importantly, energy consumption by GAC fluidization was found to be at least an order-of-magnitude lower than conventional fouling control methods employed in UF. Furthermore, redundancy analysis revealed that the key mechanism for UF fouling mitigation was tied to GAC particle momentum, whereas inorganic fouling mitigation was mostly achieved by GAC-induced liquid turbulence. It is expected that such integrated GAC-PAC-UF process proposed should be technically feasible and economically viable, potentially achieving high permeate quality and reducing membrane fouling with limited energy requirement.

Enhancing phenol removal from waste water by adding powder activated carbon to the lab-scale activated sludge system

In this study, the commercial powder activated carbon (PAC) was added to a bench scale conventional activated sludge (CAS) system to enhance phenol removal. The mixed liquor suspended solid (MLSS) concentration of CAS with adding PAC was stable in all stages of operation, while MLSS concentrations in CAS without PAC addition sharply decreased as the Phenol loading reached 1.8 g phenol/L.day. Higher removal of chemical oxygen demand (COD) and Phenol achieved with the CAS by PAC addition compared with those achieved with CAS without PAC addition. The difference in COD removal efficiency was 7 - 9% in stages 3 and 4 (0.8 and 1.2 g phenol/L.day, respectively), and about 33% in stage 5 (1.8 g phenol/L.day). The advantage of CAS with PAC addition was clearly observed in the highest phenol loading (1.8 g phenol/L.day) because the MLVSS/MLSS ratio of CAS with PAC addition increased and the COD and phenol removal efficiencies kept stable in this stage, while reverse trends were found for CAS without PAC addition. The results indicated that the adaptive ability of the CAS by adding PAC was significantly higher than the CAS without AC addition. This study offers useful preliminary results for applying a hybrid system between CAS and adsorption with PAC for further research and application in future.

Physical Properties of Starch/Powdered Activated Carbon Composite Films

In the present study, starch/powdered activated carbon composite films were prepared by incorporating various amounts of powdered activated carbon (PAC)—1–5, 10, and 15 %—into a starch matrix, using the solvent casting method. The effect of PAC addition on the biopolymer film was investigated. The mechanical properties were examined by ultra-nanoindentation, nanoscratch, and micro-tensile tests. Since the mechanical properties of biopolymer films are correlated with their structure, the effect of PAC addition was tested using X-ray diffraction. The surface parameters morphology and wettability were analyzed by atomic force microscopy (AFM) and contact angle measurements. The barrier properties were examined by determining water vapor permeability and the water solubility index. The obtained results did not show a monotonic dependence of the mechanical parameters on PAC content, with the exception of the maximum strain, which decreased as the amount of the additive increased. The visible effect of PAC addition was manifested in changes in the adhesive force value and in water vapor permeability (WVP). The barrier properties decreased with the increase of the filler content.