PAC Addition Research Articles

Feasibility study of powdered activated carbon membrane bioreactor (PAC-MBR) for source-separated urine treatment: A comparison with MBR

Micropollutants (MPs) such as pharmaceuticals and personal care products are a group of emerging environmental contaminants, which are structurally complex and can cause adverse physiological effects on human health at low concentration. This study demonstrated that a hybrid process of powdered activated carbon and microfiltration membrane bioreactor (PAC-MBR) could be utilized for efficient removal of metronidazole, acetaminophen, naproxen, ibuprofen, carbamazepine, estriol (> 99 %) from source-separated urine via physical adsorption and biodegradation in a single step, without compromising the operating system stability. PAC addition to MBR improved 5 % of nitrification performance in terms of ammonia to nitrate conversion rate. Further, it improved organic removal efficiency from 88.6 ± 2.9 % to 96.0 ± 1.2 %, promoted rapid biomass growth, increased sludge floc size growth by 17 % and reduced membrane fouling propensities. This study showed the production of a micropollutant-free fertiliser from source-separated urine achieving a complete nutrient recovery in a single stage MBR system.

Enhanced biodegradation of coal gasification wastewater (CGW) by a novel integration of powdered activated carbon treatment (PACT) coupled with wet air regeneration (WAR)

This study illustrated the advanced degradation of coal gasification wastewater (CGW) by powdered activated carbon treatment (PACT) coupled with wet air regeneration (WAR). The results demonstrated that the PACT-WAR process achieved high efficiencies on the removal of COD (92.58%), Tph (96.56%), NH4+-N (99.52%), and TN (71.52%). The PACT process was more favorable to improving the structural stability of activated sludge (AS) and the biodiversity of specific functional microbial communities. Among them, the relative abundance of Sphingopyxis, Flavobacterium, Nitrosomonas and Terrimonas was enriched to facilitate the degradation of phenolic and nitrogen compounds. More importantly, the regeneration efficiency of spent PAC was 83.33% by the WAR process, which would effectively reduce the addition of fresh PAC. The regeneration solution displayed better denitrification capacity as the additional carbon source. Therefore, the PACT-WAR process was an excellent practical process for enhancing CGW treatment.

Addition of Conductive Materials to Support Syntrophic Microorganisms in Anaerobic Digestion

Syntrophy and interspecies electron transfer among different microbial groups occurs in anaerobic digestion, and many papers recently reported their positive effect on biogas and methane production. In this paper, we present the results on the effect of conductive material, i.e., graphene, PAC and biochar addition in 3.5 L batch experiments, analyzing the biogas production curve. A peculiar curve pattern occurred in the presence of conductive materials. Compared to the respective controls, the addition of graphene produced a biogas surplus of 33%, PAC 20% and biochar 8%. Microbial community molecular analysis showed that syntrophic microorganisms present in the inoculum were stimulated by the conductive material addition. Graphene also appears to promote an interspecies electron transfer between Geobacter sp. and ca. Methanofastidiosum. This paper contributes to the understanding of the DIET-related microbial community dynamic in the presence of graphene and PAC, which could be exploited to optimize biogas and methane production in real-scale applications.

PAC-UF Process Improving Surface Water Treatment: PAC Effects and Membrane Fouling Mechanism.

In this study, the water purification effect and membrane fouling mechanism of two powdered activated carbons (L carbon and S carbon) enhancing Polyvinylidene Fluoride (PVDF) ultrafiltration (UF) membranes for surface water treatment were investigated. The results indicated that PAC could effectively enhance membrane filtration performance. With PAC addition, organic removal was greatly enhanced compared with direct UF filtration, especially for small molecules, i.e., the S-UF had an additional 25% removal ratio of micro-molecule organics than the direct UF. The S carbon with the larger particle size and lower specific surface area exhibited superior performance to control membrane fouling, with an operation duration of S-UF double than the direct UF. Therefore, the particle size and pore structure of carbon are the two key parameters that are essential during the PAC-UF process. After filtration, acid and alkaline cleaning of UF was conducted, and it was found that irreversible fouling contributed the most to total filtration resistance, while the unrecoverable irreversible resistance ratio with acid cleaning was greater than that with alkaline cleaning. With PAC, irreversible UF fouling could be relieved, and thus, the running time could be extended. In addition, the membrane foulant elution was analyzed, and it was found to be mainly composed of small and medium molecular organic substances, with 12% to 21% more polysaccharides than proteins. Finally, the hydrophilicity of the elution was examined, and it was observed that alkaline cleaning mainly eluted large, medium, and small molecules of hydrophilic and hydrophobic organic matter, while acid cleaning mainly eluted small molecules of hydrophilic organic matter.

Effect of clariflocculator and pulsator based sedimentation technology and poly-aluminium chloride coagulant type on the efficiency of the water treatment plant

Abstract Polyaluminium chloride (PAC) with different basicity is used as a coagulant in most drinking water treatment plants (WTP). The aluminium concentration in PAC and its hydrolysis mechanism varied with the basicity of PAC. Incremental addition of PAC changes various physico-chemical properties and turbidity removal mechanisms in water. Water treatment plants use the PAC concentration beyond its optimum dose without considering other aspects, including residual aluminium concentration. In the present work, the effect of high and medium basicity of PAC on different physico-chemical properties like pH, zeta potential, and residual aluminium concentration of water was investigated. The pH of treated water decreases with the incremental addition of PAC, and an increase in zeta potential and residual aluminium concentration in treated water was evidenced. The change in pH after PAC addition is responsible for deciding the coagulation mechanism and efficiency of the coagulation process. pH reduction is comparatively more in high basicity PAC than medium basicity. PAC hydrolysis mechanism is controlled by the zeta potential of water and can be used as an alternative method to decide the optimum coagulant dose. The performance of clariflocculator and pulsator-based WTP was also evaluated for raw water from the same source. To reduce down the turbidity below the acceptable level, the coagulant requirement for clariflocculator based WTP is comparatively less than pulsator based WTP. The floc blanket in the pulsator gets disturbed with a slight change in the coagulant chemistry and quantity.

Antimony removal from textile wastewater by combining PFS&PAC coagulation: Enhanced Sb(V) removal with presence of dispersive dye

• Combining PFS&PAC coagulation is proposed to remove ppb-level Sb(V). • Enhanced Sb(V) removal is achieved with presence of dispersive black UD. • Combining PFS&PAC coagulation also removes turbidity caused by dispersive dye. • The removed Sb(V) is bound with O atom originated from PFS hydrolysis. • Flocs derived from combining PFS&PAC can adsorb much more Sb(V) in 30 min. Antimony (Sb) is a typical contaminant in textile wastewater due to its extensive use in fabric production. Although Fe coagulant shows good performance towards Sb in simulated condition, co-existing components such as dye, coexisting ion, and humic acid (HA) in actual textile wastewater would hinder its application. This study proposes a combination of poly ferric sulfate and poly aluminum chloride (PFS&PAC) to remove ppb-level Sb(V) from both simulated and actual textile matrix with presence of typical dispersive dye. By optimizing the operating parameters, maximum Sb(V) removal efficiency of 95.0% is observed with coexistence of 100 mg L −1 dispersive black UD at pH 3, with dosage of 200 mg L −1 PFS and 100 mg L −1 PAC. The response surface methodology indicates that nitrate and chloride have negligible effect on the Sb(V) removal capacity, while HA and phosphate inhibit Sb(V) removal. When compared with PFS, combining PFS&PAC coagulation also reduces the turbidity caused by dispersive black UD in both simulated (from 450 to 22 NTU) and actual textile wastewater (from 116 to 42 NTU). The XPS spectra of flocs suggests that Sb(V) can be bounded with O atom. Aging test suggests the PAC addition retards transformation of flocs from amorphous ferrihydrite to crystalline phases, thus providing more active adsorption sites for Sb(V) removal with presence of competing dispersive dye. Newly produced flocs derived from combining PFS&PAC coagulation can adsorb 63% Sb(V) in 30 min, which is 2.3 folds than that of PFS only.

Distinct granulation pathways of aerobic granular sludge under poly aluminum chloride enhancement

Aerobic granular sludge (AGS), a novel strategy for nutrient removal which exhibits compact structure, good settleability, and resilience against high organic load, has been considered as a highly potential wastewater treatment technology. However, the long start-up period for granulation prevented its widespread development. In this study, the distinct pathways of PAC-enhanced AGS granulation were systematically investigated. Four identical sequencing batch reactors (SBR) with different PAC dosages (with 0, 50, 100, 400 mg/L effective Al3+ respectively) were applied. It was observed that the presence of PAC accelerated granules formation, promoted mechanical strength as well as denitrification rate of granules, and thus notably enhanced removal efficacies of COD, NH4+-N, NO2− and NO3−. According to the dissolved oxygen (DO) distribution inside the sludge and the denitrification rate (SDNR) measurements, distinguishing structures of granules under different PAC addition were discovered. Comparatively, AGS under low PAC addition (i.e., 50 mg/L) resulted in the largest granule size, the biggest anaerobic zone and the highest denitrification rate. Presumably, for the system with the low PAC addition (50 mg/L), appropriate aluminum ions (Al3+) neutralized part of the negative charge on the microorganism surface, thereby promoting cells aggregation. In contrast, a high dosage of PAC (400 mg/L) induced excessive Al3+ absorbed on the cell surface after neutralization, which increased the repulsive force between microorganisms, leading to more cavities and channels existed inside the granules. Therefore, granules under low PAC dosage (i.e., 50 mg/L) presented large anaerobic zone and high denitrification rate, thus favored the best internal structure and nutrients removal efficiencies.

Starch and powdered activated carbon amended alginate-biomass beads for metronidazole and bulk organic matter removal: Synthesis, optimization, reaction kinetics and reusability

In this work, biomass immobilized alginate beads were amended with various ratios of starch (0–20%) and powdered activated carbon (PAC: 0–0.1%), and optimum compositions were shortlisted based on simultaneous removal of metronidazole (MNZ) and organic matter from synthetic wastewater. MNZ removal of greater than 80% was achieved for initial MNZ concentration of 1 ppm in 3d with optimum PAC (0.1%) and starch (5%) ratios. The presence of additional carbon substrate (i.e., dextrose) had improved the MNZ removal efficiency. Subsequently, the experiments were conducted with alginate beads amended with 0.1% PAC (A1-C2), 5% starch (A1-S1) and combination of 0.1% PAC and 5% starch (A1-S1-C2) The MNZ removal by PAC and starch amended beads was found to follow the second-order and first-order kinetics, respectively. Compared to starch amended beads, average MNZ, organic carbon and nitrogen removal efficiencies of PAC amended beads were higher by 12%, 32% and 5%, respectively. Moreover, reusability study had shown better stability of PAC (8 cycles) compared to starch (3 cycles). When starch and PAC were added together, the removal efficiencies were better than starch but lower than PAC except in the case of ammonia removal. Among the shortlisted beads, A1-C2 was found to perform best in MNZ, TOC and ammonia removals. PAC addition improved MNZ removal efficiency and the MNZ removal rate. The involvement of both adsorption and biodegradation were established in MNZ removal in all types of beads by FTIR and LC-MS analysis, respectively. However, simultaneous and rapid removal of MNZ along with organic carbon by adsorption paired with subsequent biodegradation demonstrate the applicability of A1-C2 for the treatment of PPCP laden wastewaters.

What are the effects of portable air cleaners with a high-efficiency particulate air filter on aerosol removal in dental surgeries?

Design Volumetric air flow was measured in a number of dental surgeries to calculate the air change rate per hour (ACHvent). In each surgery, measurements of aerosol removal by ventilation alone, and then with ventilation provided by a high-efficiency particulate air filter (PAC), were completed. The concentrations of aerosol particles of various sizes were recorded at baseline, after an initial period of incense burn, and then after 30 minutes of observation with and without the use of the PAC or ventilation system.Sample selection Ten dental surgeries with differing baseline ventilation rates had the concentrations of 0.3, 0.5 and 1.0 μm aerosol particles measured at 0 minutes, after 5 minutes of incense burn and then after 30 minutes of observation, firstly without the PAC system in operation and then with the PAC system in use.Data analysis For the 0.3 μm particles, velocities of aerosol removal were assessed by analysing the concentration decay constants with ventilation alone and ventilation with the PAC. Aerosol removal velocities were assessed by the time needed to reach 95% and 100% removal of accumulated aerosol particles.Results ACHvent in the ten different surgeries varied from 3-45. The concentration decay constants for the 0.3 μm particles with ventilation alone and ventilation with the PAC were correlated to the mechanical ventilation rate and combined respectively. For rooms with ACHvent of less than 15, accumulated aerosol particles could not be removed by ventilation alone in 30 minutes. The PAC accelerated aerosol removal and reduced aerosol accumulation, and with the use of the PAC in addition to ventilation, accumulated aerosols were removed completely in 4-12 minutes. The PAC was shown to be more beneficial in rooms with poor ventilation and the added effectiveness of the PAC in aerosol removal was inversely correlated with the ACHvent by ventilation.Conclusions Although the air change rate differed considerably among dental surgeries, this study suggests that the addition of the PAC with a HEPA filter significantly increased aerosol removal and lessened aerosol accumulation, particularly in rooms with low ventilation rates.

Effect and mechanism of reduced membrane bioreactor fouling by powdered activated carbon.

Powered Activated Carbon - Membrane Bioreactors (PAC-MBRs) have been used with good results for slightly polluted water treatment. Our batch experiments showed that the transmembrane pressure of a PAC-MBR was 25% less than that of a MBR in one period of test, which indicated that PAC did help control the fouling in MBRs. Based on this observation, several mechanisms of membrane fouling of MBRs and PAC-MBRs were investigated to have some insight into how PAC brought a positive impact. The total resistances decreased by 60% and different resistances were redistributed after adding PAC. The dominant one changed from filtration resistance to cake resistance. These smaller cake resistances resulted from the PAC because, showing in the scanning electron microscopy pictures, it made the cake layer looser and rougher than that on a normal membrane. Meanwhile, the analysis of the membrane eluent showed that the addition of PAC changed the microbial species and its metabolites on the membrane and effectively reduced the adsorption of hydrophilic organic molecules on the membrane surface. Additionally, PAC prevented polypeptide compounds from being trapped inside the pores of membranes, so the cake on the PAC-MBR contaminated membrane surface was easier to scrape off. In the test of cleaning methods, alkaline cleaning removed the most organics from contaminated membranes to restore membrane performance.

To what extent may pharmaceuticals and pesticides be removed by PAC conventional addition to low-turbidity surface waters and what are the potential bottlenecks?

Pilot runs of powdered activated carbon/coagulation/flocculation/sedimentation (PAC/CFS) were conducted to investigate the removal of 19 pharmaceutical compounds and 9 pesticides as a function of their properties. PAC addition impact on the clarification effectiveness of low-turbidity surface waters was also explored. Four sets of operating conditions tested different PAC types, doses and contact times. Removals of 65–79 % for total-pharmaceuticals and 73–83 % for total-pesticides were achieved with 3−9 mg/L of a mesoporous PAC or with 20−24 mg/L of a microporous PAC. Microcontaminants’ key properties for adsorption were charge, hydrophobicity and aromaticity. For low-hydrophobicity compounds, positively charged functional groups and low surface polar area and/or high number of aromatic rings acted as adsorption enhancers. The positively charged compounds were better removed than the negatively charged ones, an effect stronger for the negatively charged PAC. Results show PAC dose reduced to half/one-third using an adequate PAC and to one-quarter/one-eighth with additional 1-h contact time. PAC dose saving is crucial, for economic and environmental reasons and for PAC/CFS effectiveness. PAC addition, particularly above 10 mg/L PAC, hampered the clarification of the low-turbidity waters studied towards residual turbidity, aluminium and aerobic endospores, and may require a reliable downstream filtration to retain PAC fines.

Treatment of municipal wastewater in AnMBRs with powdered activated carbon addition under psychrophilic temperatures.

The performance of anaerobic membrane bioreactors (AnMBRs) at psychrophilic temperatures commonly observed in temperate climates (10-24°C) was assessed. A unique aspect of the research was operation at controlled SRT with regular membrane cleaning. COD removal and permeate VFA concentrations were similar at 15 and 24°C and deteriorated at 10°C. As temperature decreased, the COD mass flow to methane decreased and COD mass flows in the permeate and waste sludge increased. At 24°C, rapid membrane TMP increases were not observed while at 15 and 10°C rapid increases occurred at 11.7±0.46 and 7.6±0.45days, respectively, indicating a greater fouling propensity of the mixed liquor at lower temperatures. When the temperature was reduced from 15°C to 10°C in a transient test, CH4 production was reduced and VFA concentrations increased. A 2-3 SRT lag in the responses suggested that the delayed response was due to long-term changes in microbial population. The permeate VFA content in a PAC-dosed reactor was lower than that without PAC dosing, and PAC addition increased the time to rapid TMP development to 11.3±0.46days from 7.4±0.49days. The primary benefit of PAC addition at low temperatures is enhanced membrane performance. PRACTITIONER POINTS: AnMBRs can produce high-quality effluents at temperatures of 15°C Membrane fouling increases as temperature decreases Bioreactor performance was sustained for 2-3 SRTs after temperature decrease PAC addition reduced the permeate VFA concentrations Membrane fouling at 10°C was reduced through PAC addition.

Comparing powdered and granular activated carbon addition on membrane fouling control through evaluating the impacts on mixed liquor and cake layer properties in anaerobic membrane bioreactors

Concerning the lack of comprehensive study on the impact of powdered and granular activated carbon (PAC and GAC) on AnMBR, their impact on treatment performance, mixed liquor and cake layer properties and membrane fouling behaviors were further investigated. High COD removal efficiencies (>90%) and COD converting to CH4 rates (>70%) were achieved. GAC greatly increased extracellular polymeric substances (EPS) production in mixed liquor, but significantly reduced biosolids deposited on membrane surface; while PAC largely increased proteins and polysaccharides on membrane surface. In addition, PAC decreased, whereas GAC increased particle sizes. Fouling rates showed PAC and GAC addition effectively alleviated membrane fouling at HRT 8 h, and GAC remarkably postponed the occurrence of the transmembrane pressure jump and extended membrane service time. This study clarified the roles of GAC and PAC on membrane fouling control over long-term operation, which provides the basis for decision-making in practical application.

Anaerobic bioaugmentation hydrolysis of selected nitrogen heterocyclic compound in coal gasification wastewater

Anaerobic bottle experiments were conducted in parallel for 120 consecutive days to perform the bioaugmentation hydrolysis of selected nitrogen heterocyclic compounds (NHCs) in coal gasification wastewater. Due to enhancement with PAC and Fe(OH)3@PAC, quinoline, pyridine, and indole were hydrolyzed more effectively. The addition of PAC and Fe(OH)3@PAC improved the coagulation capacity of microorganisms, which laid a solid foundation for the removal of selected NHCs and the adverse environmental conditions. Anaerobic degradation of the NHCs occurred first through hydrogenation, then through the opening of the nitrogen heterocycles, followed by the release of ammonia nitrogen and finally the opening of the benzene rings. Enriched Acinetobacter, Levilinea, Comamonas, and Longilinea were the main functional groups responsible for the anaerobic biodegradation of the selected NHCs.

Effects of powdered activated carbon addition on filtration performance and dynamic membrane layer properties in a hybrid DMBR process

A powdered activated carbon-dynamic membrane bioreactor (PAC-DMBR) was developed and used to treat domestic wastewater by dosing with 3g/L PAC. The experimental results were compared with those of a control DMBR to investigate the filtration performance and various properties of the dynamic membrane (DM) layer. One flat-sheet DM module made of nylon mesh (pore size 75μm) was used for effluent production at a high stable flux (50–100L/m2h) under a 10cm water head by gravity flow, resulting in continuous operation cycles of 60–120h. During the operation period, the PAC-DMBR showed enhanced removal efficiency of pollutants, higher stable membrane flux (10L/m2h more), lower filtration resistance (6.0–8.0×1010m−1), quicker formation of the DM layer (within 5min), and better DM layer regeneration after air backwashing. The DM layer in the PAC-DMBR showed a more porous and incompressible structure, because less extracellular polymeric substance and a portion of the biological PAC were incorporated into the DM layer formed as verified by the analytical results. Using high-throughput pyrosequencing technology, it was revealed that at the genus level the diversity of bacterial communities increased from 18 to 23 genera, while several genera that were favored in the PAC-assisted environment or were responsible for degrading complex organics were enriched. Moreover, the abundance of phylum Proteobacteria, which served as pioneer surface colonizers, was reduced in the PAC-DMBR. It was concluded that PAC addition could modify various aspects of the activated sludge and the DM layer properties, which affected the filtration behavior of the DM layer in the PAC-DMBR.

Organic micropollutants (OMPs) oxidation by ozone: Effect of activated carbon on toxicity abatement

Oxidation and removal of organic micropollutants (OMPs) on ultrapure (UPW) and natural water (NW) by ozone (O3) and ozone/powdered activated carbon (O3/PAC) have been studied. The OMPs atrazine (ATZ, herbicide), carbamazepine (CBZ, anticonvulsant), diclofenac (DCL, anti-inflammatory) and triclosan (TCS, antimicrobial) are incorporated continuously and uncontrolled on water treatment systems (e.g., drinking water treatment plants, wastewater treatment plants).Batch experiments on ultrapure and natural water showed that ATZ treated with O3 and O3/PAC has the slowest transformation rate (>90% at 30min reaction) while CBZ, DCL and TCS were oxidized very fast (>90% at ~5min). The radical scavenger tert-Butyl alcohol (TBA) was used to evaluate the contribution of HO on the OMPs oxidation. TBA, a hydrophilic compound with low adsorbability, was used as a strong HO scavenger to assess the role of the OH radical in the oxidation of the OMPs studied. ATZ oxidation was mainly driven by OH radicals. On the contrary, CBZ, DCL and TCS were removed by direct reaction with ozone. Infrared analysis (FTIR) showed changes in the PAC surface functional groups of the carbon exposed to ozone, decreasing its basic properties.The acute toxicity assays of the OMPs mixture dissolved in UPW performed with D. magna was significantly reduced by ozonation. The addition of PAC to the ozonation process, strongly improved the acute toxicity removal. Short chain mono- and di-carboxylic acids were identified as some of the oxidation intermediates formed during ozone treatment.

Removal of 17α-ethynylestradiol from aqueous solutions by a hybrid PAC/UF process

This study investigated the removal of 17α-ethynylestradiol (EE2) from water using activated carbon adsorption and powdered activated carbon/ultrafiltration (PAC/UF). EE2 was easily adsorbed by PAC. The adsorption of EE2 fitted the Freundlich model well. The influences of initial EE2 concentration, filtration rate, PAC dose, natural organic matter (NOM), and sodium dodecyl benzene sulfonate (SDBS) were investigated. The EE2 concentration and filtration rate had no significant effect on EE2 removal, whereas the addition of PAC had a significant effect on EE2 removal. The removal rate of EE2 increased dramatically from 7.01% to 80.03% as the PAC dose was increased from 0 to 10 mg/L. Both SDBS and NOM decreased the EE2 removal efficiency. The removal efficiency of EE2 in the PAC/UF process decreased from 86.77% to 42.64% as the SDBS concentration was increased from 0 to 50 mg/L. It was concluded that activated carbon adsorption and PAC/UF can be used for the effective removal of EE2 from water.

Characterization of a hybrid powdered activated carbon-dynamic membrane bioreactor (PAC-DMBR) process with high flux by gravity flow: Operational performance and sludge properties

Three PAC-DMBRs were developed for wastewater treatment under different PAC dosages with biomass concentrations averaged at 2.5, 3.5 and 5.0g/L. The DMBRs could be continuously operated at 40–100L/m2h, while higher fluxes were obtained within the PAC-DMBRs with hydraulic retention times varying in 4–10h. A dose of 1g/L PAC brought about obvious improvement in the sludge particle size distribution, settling, flocculating and dewatering properties due to the formation of biological PAC, and the sludge properties were further improved at a higher PAC dose (3g/L). The addition of PAC notably shortened the DM formation time after air backwashing and enhanced pollutant removal. Moreover, under a long solid retention time (approximately 150d), the concentrations of both soluble and bound extracellular polymeric substances (EPS) decreased substantially because of the adsorption and biodegradation effects of the biological PAC. No obvious impact on biomass activity was observed with PAC addition.

Micro-polluted surface water treatment and trace-organics removal pathway in a PAC-MBR system

Trace-organic contaminants elimination effectiveness and their removal pathways in a powder-activated carbon-membrane bioreactor (PAC-MBR) used for micro-polluted surface water treatment were investigated in this study. The results showed that PAC-MBR was capable of consolidating DOM elimination, enhancing trace-organic contaminants (2,4,6-trichlorophenol, nitrobenzene and trichloroethylene) removal efficiency, improving permeate biostability, and decreasing bulk organic content and specific fractional components, which was beneficial for membrane fouling mitigation. By series of well-designed batch-tests and estimation, trace-organics removal pathways were analyzed. The primary way of TCE removal was aeration volatilization, while that of NB and 2,4,6-TCP elimination was biodegradation which was greatly affected by biomass content within bulk. PAC addition was a positive way for effective trace-organics removal by increasing mixed solid adsorption capability, especially in start-up phase, and offering beneficial circumstances for biomass enrichment and functional bacteria accumulation. Thus, PAC addition into MBR is a simple and effective strategy to treat micro-polluted water resources.

Controlling a toxic shock of pentachlorophenol (PCP) to anaerobic digestion using activated carbon addition

Several powdered and granular activated carbons (PACs and GACs) were tested for adsorption of pentachlorophenol (PCP) in bench-scale anaerobic digestion reactors to control the toxicity of PCP to acetoclastic methanogenesis. Results showed that the adsorption capacities of PAC were reduced by 21–54%, depending on the PAC addition time, in the presence of the methanogenic sludge compared to the controls without sludge. As a preventive measure, PAC at a low dose of 20% (mass ratio to the VSS) added 24h prior to, or simultaneously with, the addition of PCP could completely eliminate the toxic effects of PCP. At the same dose, PAC also enabled methanogenesis to recover immediately after the sludge had been exposed to PCP for 24h. GAC was not effective in enabling the recovery of methanogenesis due to its slow adsorption kinetics; however, at a dose of 80% it could partially ameliorate the toxic shock of PCP.