Effect of powdered activated carbon on Chinese traditional medicine wastewater treatment in submerged membrane bioreactor with electronic control backwashing

Chinese traditional medicine wastewater, rich in macromolecule and easy to foam in aerobic biodegradation such as Glycosides, was treated by two identical bench-scale aerobic submerged membrane bioreactors （SMBRs） operated in parallel under the same feed, equipped with the same electronic control backwashing device. One was used as the control SMBR （CSMBR） while the other was dosed with powdered activated carbon （PAC） （PAC-amended SMBR, PSMBR）. The backwashing interval was 5 min. One suction period was about 90 min by adjusting preestablished backwashing vacuum and pump frequency. The average flux of CSMBR during a steady periodic state of 24 d （576 h） was 5.87 L/h with average hydraulic residence time （HRT） of 5.97 h and that of PSMBR during a steady periodic state of 30 d （720 h） was 5.85 L/h with average HRT of 5.99 h. The average total chemical oxygen demand （COD） removal efficiency of CSMBR was 89.29% with average organic loading rate （OLR） at 4.16 kg COD/（m^3.d） while that of PSMBR was 89.79% with average OLR at 5.50 kg COD/（m^3.d）. COD concentration in the effluent of both SMBRs achieved the second level of the general wastewater effluent standard GB8978-1996 for the raw medicine material industry （300 mg/L）. Hence, SMBR with electronic control backwashing was a viable process for medium-strength Chinese traditional medicine wastewater treatment. Moreover, the increasing rates of preestablished backwashing vacuum, pump frequency, and vacuum and flux loss caused by mixed liquor in PSMBR all lagged compared to those in CSMBR; thus the actual operating time of the PSMBR system without membrane cleaning was extended by up to 1.25 times in contrast with the CSMBR system, and the average total COD removal efficiency of PSMBR was enhanced with higher average OLR.

Study on Regeneration of Powdered Activated Carbon by Electron Beam

The powdered activated carbon which had adsorbed phenylglycine solution from pharmaceutics factory can be regenerated by mean of irradiation of high-energy electron beams in oxygen, nitrogen and water vapor respectively. The effects of radiation dose and beam current on regeneration of activated carbon in different atmosphere were studied. Differential scanning calorimetry (DSC) and the iodine number of activated carbon were used to monitor the change of carbon adsorption. The results show that the powder activated carbon polluted with phenlglycine could be regenerated effectively by irradiation of high energy electron beams in nitrogen stream. The generation did not need high temperature, and the weight loss of carbon and energy consumption were minimum.

Adsorption Characteristics of the Powdered Activated Carbon on Pesticide in the Water

The adsorption characteristics of the powdered activated carbon on four kinds of pesticides （ dichlorvos, chlorothalonil, lindane and chlorphyrifos） were studied, and the influential factors of adsorption effect were discussed. Results showed that the powdered activated carbon could effectively remove the above four kinds of pesticides. It was rapid adsorption period before 30 min, and removal rate has reached 90%. Adsorption kinetics of the powdered activated carbon on pesticides corresponded with quasi-two-level kinetic equation, and both Freundlich and Langmuir adsorption isotherms could simulate the adsorption process of the activated carbon on pesticide well. Competitive adsorption between small-molecule organics in the water diverting from Yellow River and Desticides on microDore of the activated carbon would occur.

Enhanced Adsorption of Pb(II) Ions from Aqueous Solution by Persimmon Tannin-activated Carbon Composites

The modification of activated carbon with persimmon tannin and its application for the removal of Pb（II） ions were carried out by batch method. The effects of solution pH, contact time, temperature and initial concentration on the immobilization of persimmon tannin were studied. The experimental results showed that the experimental data of persimmon tannin and Pb（II） fitted better by Langrnuir adsorption isotherm model and pseudo-second order model. The adsorption capacities of adsorbents for persimmon tannin and Pb（II） were calculated from the Langmuir isotherm model, and found to be 42.97 and 12.40 mg/g at optimum pH, respectively. It was noted that the adsorbent exhibited the best adsorption property for Pb（lI） when 1.0 g activated carbon was modified by 17.32 mg persimmon tannin. The modified activated carbon is more effective than the plain activated carbon, and it is expected to be an economic and effective adsorbent for the disposal of wastewater containing Pb（II） ions.

Pilot Study on Powder Active Carbon / Flotation/Microflocculation / Ultrafiltration Combined Process for Treatment of Reservoir Water

[Objective] The study aimed to discover the effects of powder active carbon（ PAC） /flotation /micro-flocculation /ultrafiltration combined process on the treatment of reservoir water. [Method]Taken the water from a mountainous reservoir for the initial samples,the parameters such as turbidity,COD Mn,chlorophyll-a and methylisobormeol（ MIB） of water samples were monitored before and after treated with combined processes of micro-flocculation /ultrafiltration, flotation /micro-flocculation /ultrafiltration, PAC /flotation /micro-flocculation /ultrafiltration. [Result] The results showed that the removal rates of turbidity of water samples by the above three processes were 97. 5%,98. 0% and 98. 6%,respectively. The removal rates of COD Mn were 30. 9%,35. 0% and 52. 0%. The removal rates of chlorophyll-a were 80. 6%,91. 0% and 99. 0%. The removal rates of MIB were 17. 0%,34. 2% and 97. 0%. [Conclusion]The PAC /flotation /micro-flocculation ultrafiltration combined process can be flexibly combined based on the characteristics of algae and odor in water,and is suitable for water plant construction or reconstruction.

Uptake of copper ion by activated sludge and its bacterial community variation analyzed by 16S rDNA

The effect and uptake of copper ion on SBR(sequence batch reactor) biological treatment system was studied. Special nutrient and powder activated carbon(PAC) additive were tested as uptake stimulation technique. Results showed that copper ion had higher effect on unacclimated activated sludge system than on acclimated one. The special nutrient adding could enhance the uptake of copper significantly, while PAC adding could improve the sludge settling and decrease the turbidity of effluent. The variation of bacterial community analyzed by 16S rDNA method showed the acclimation of copper could increase copper resistance species, and excess accumulation could cause some species diminish. It was confirmed that acclimation could improve the resistance and uptake ability of microorganism to heavy metal.

Mechanism of powdered activated carbon enhancing caproate production

Caproate, produced by microbial chain elongation process, is potential to replace the diversified fossilbased 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-Co A, and simultaneously boosted the efficiency of reverse β oxidation(RBO) by promoting the timely reaction of butyrate and acetyl-Co A to synthesis caproate. The addition of PAC also shifted the microbial community by enriching more caproateproducing 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.

Simultaneous removal of ammonia and N-nitrosamine precursors from high ammonia water by zeolite and powdered activated carbon

When adding sufficient chlorine to achieve breakpoint chlorination to source water containing high concentration of ammonia during drinking water treatment, high concentrations of disinfection by-products（DBPs） may form. If N-nitrosamine precursors are present, highly toxic N-nitrosamines, primarily N-nitrosodimethylamine（NDMA）, may also form. Removing their precursors before disinfection should be a more effective way to minimize these DBPs formation. In this study, zeolites and activated carbon were examined for ammonia and N-nitrosamine precursor removal when incorporated into drinking water treatment processes.The test results indicate that Mordenite zeolite can remove ammonia and five of seven N-nitrosamine precursors efficiently by single step adsorption test. The practical applicability was evaluated by simulation of typical drinking water treatment processes using six-gang stirring system. The Mordenite zeolite was applied at the steps of lime softening, alum coagulation, and alum coagulation with powdered activated carbon（PAC） sorption. While the lime softening process resulted in poor zeolite performance, alum coagulation did not impact ammonia and N-nitrosamine precursor removal. During alum coagulation, more than67% ammonia and 70%–100% N-nitrosamine precursors were removed by Mordenite zeolite（except 3-（dimethylaminomethyl）indole（DMAI） and 4-dimethylaminoantipyrine（DMAP））. PAC effectively removed DMAI and DMAP when added during alum coagulation. A combination of the zeolite and PAC selected efficiently removed ammonia and all tested seven N-nitrosamine precursors（dimethylamine（DMA）, ethylmethylamine（EMA）, diethylamine（DEA）, dipropylamine（DPA）, trimethylamine（TMA）, DMAP, and DMAI） during the alum coagulation process.

Removal of bromate ion using powdered activated carbon

Bromate ion （BrO3-） removal from drinking water by powdered activated carbons （PACs） in bath mode was evaluated under various operational conditions. Six kinds of PACs, including wood-based carbon, fruit-based carbon, coal-based carbon, and these three carbons thermally deoxidized in a nitrogen atmosphere, were selected to investigate their capacity on BrO3- removal. With the highest zeta potential value and being richly mesoporous, coal-based carbon had a high and an excellent BrO3- adsorption efficiency. The removal content of BrO3- by per gram of coal-based carbon was 0.45 mg within 5 hr in 100 μg/L bromate solution. The surface characteristics of PACs and bromide formation revealed that both physical and chemical PACs properties simultaneously affected the adsorptionreduction process. Under acidic conditions, PACs possessed high zeta value and adequate basic groups and exhibited neutral or positive charges, promoting BrO3- adsorption-reduction on the carbon surface. Interestingly, the PACs thermally deoxidized in N2 atmosphere optimized their properties, e.g. increasing their zeta values and decreasing the oxygen content which accelerated the BrO3- removal rate. The maximum adsorption capacity of fruit-based carbon was the highest among all tested carbons （99.6 mg/g）, possibly due to its highest pore volume. Remarkably, the thermal regeneration of PACs in N2 atmosphere could completely recover the adsorption capacity of PACs. The kinetic data obtained from carbons was analyzed using pseudo second-order and intraparticle diffusion models, with results showing that the intraparticle diffusion was the more applicable model to describe adsorption of BrO3- onto PACs.

Removal of phenol by powdered activated carbon adsorption

In this study, the adsorption performance of powdered activated carbon （PAC） on phenol was investi- gated in aqueous solutions. Batch adsorption studies were performed to evaluate the effects of various experimental parameters like PAC type, PAC dose, initial solution pH, temperature and pre-oxidation on the adsorption of phenol by PAC and establish the adsorption kinetics, thermo- dynamics and isothermal models. The results indicated that PAC adsorption is an effective method to remove phenol from water, and the effects of all the five factors on adsorption of phenol were significant. The adsorption rate of phenol by PAC was rapid, and more than 80% phenol could be absorbed by PAC within the initial 10 min. The adsorption process can be well described by pseudo- second-order adsorption kinetic model with rate constant amounted to 0.0313, 0.0305 and 0.0241 mg.μg .min -1 with coal, coconut shell and bamboo charcoal. The equilibrium data of phenol absorbed onto PAC were analyzed by Langmuir, Freundlich and Tempkin adsorp- tion isotherms and Freundlich adsorption isotherm model gave the best correlation with the experimental data. Thermodynamic parameters such as the standard Gibbs free energy （△G0）, enthalpy （△H0） and entropy （△S0） obtained in this study indicated that the adsorption of phenol by PAC is spontaneous, exothermic and entropy decreasing.

STUDY ON THE EROSION RATE OF POWDERED ACTIVATED CARBON IN RAW WATER AQUEDUCT

Growing interest in using Powdered Activated Carbon （PAC） in raw water aqueduct, as a method of polluted surface water treatment, raises the question of transport of PAC in the aqueduct, which is related to the potential PAC erosion along the aqueduct. By means of a recently developed re-circulating flume, erosion rates of PAC with the grain size of 230 meshes （less than 62μm） depending on shear stress and bulk density were the discussed with real-time measurement of suspended PAC concentration. Lateral cross sectional averaging shear stress was decided by the actual value in the raw water conveying aqueduct of upstream Huangpu River, Shanghai, China, smaller than 1.8 N＇m 2. As for the bulk density, it was measured with compacting times varying from 1 d to 15 d, equivalent to 1 550 kg/m3-1 800 kg/m3. Experiments were conducted for the shear stress and bulk density separately, so as to isolate and quantify the effects of one of the parameters. The results demonstrate that, for a particular PAC particle, the erosion rate increases with shear stress and decreases with bulk density as a function of power form. A product of powers of the lateral cross sectional averaging shear stress and bulk density to estimate PAC erosion rate is presented by approximating experimental data sets.

Study on transport of powdered activated carbon using a rotating circular flume

This study employed a rotating flume to examine the Powdered Activated Carbon （PAC） transport with water flow. The initial PAC concentration was 10 mg/L-30 mg/L, and PAC concentration versus time under a specified cross-sectional averaging fluid shear was observed. Results show that compared with PAC deposition in still water, PAC is depleted to zero faster under a fluid shear of 0.02 Pa, due to PAC agglomeration with the fluid shear. However, since PAC floc size only ranges from a single particle （2 μm） to approximate 6 μm, an increasing of instantaneous turbulent fluctuations could counteract the force of PAC floc settling downward, and as a result the steady PAC concentration increases with the increase of shear stress. It is found that the critical shear stress for PAC deposition is about 0.60 Pa, and further the PAC deposition probability is presented according to the experimental scenarios between 0.02 Pa and 0.60 Pa. Combining the PAC transport and deposition formula with PAC-pollutant removal model provides an insight into PAC deployment in raw water aqueduct for sudden open water source pollution.

Drinking water production by uitrafiltration of Songhuajiang River with PAC adsorption

In recent years, membrane ultrafiltration （UF） of surface water for drinking water treatment has become a more attractive technology worldwide as a possible alternative treatment to conventional clarification. To evaluate the performance of ultrafiltration membranes for treatment of surface water in North China, a 48-m^2 low pressure hollow fiber membrane ultrafiltration pilot plant was constructed. Ultrafiltration was operated in cross-flow and with powdered activated carbon （PAC） adsorption. Turbidity was almost completely removed to less than 0.2 NTU （below Chinese standard 1 NTU）. It was found that PAC addition enhanced organic matter removal. The combined process of PAC/UF allowed to 41% removal of CODMn, 46% removal of DOC and 57% decrease in UV254 absorbance. The elimination of particles, from average 12000/ml in the raw water to approximately 15/ml in the permeated, was observed. When PAC concentration was below 30 mg/L, backwashing could recovery the membrane flux with backwash interval/backwashing duration of 1/30.

Comparative study on the removal technologies of 2-methylisoborneol(MIB) in drinking water

Removal of 2-methylisoborneol （MIB） in drinking water by ozone, powdered activated carbon （PAC）, potassium permanganate and potassium ferrate was investigated. The adsorption kinetics of MIB by both wood-based and coat-based PACs show that main removal of MIB occurs within contact time of 1 h. Compared with the wood-based PAC, the coat-based PAC evidently improved the removal efficiency of MIB. The removal percentage of trace MIB at any given time for a particular carbon dosage was irrelative to the initial concentration of MIB. A series of experiments were performed to determine the effect of pH on the ozonation of MIB. The results show that pH has a significant effect on the ozonation of MIB. It is conclusive that potassium permanganate and potassium ferrate are ineffective in removing the MIB in drinking water.

The influence of chlorinated aromatics＇ structure on their adsorption characteristics on activated carbon to tackle chemical spills in drinking water source

This study focused on evaluating the efficiency of powdered activated carbon （PAC） adsorption process and tackling chlorobenzenes and chlorophenols spill in drinking water source. The adsorption kinetics and PAC＇s capacities for five chlorobenzenes and three chlorophenols at drinking water contamination levels were studied in order to determine the influence of different functional groups on the adsorption behavior. The results showed that PAC adsorption could be used as an effective emergency drinking water treatment process to remove these compounds. The adsorption kinetics took 30 min to achieve nearly equilibrium and could be described by both pseudo first-order and pseudo second-order models. A mathematic relationship was developed between the pseudo first-order adsorption rate constant, k1, and the solutes＇ properties including lgKow, polarizability and molecular weight. The Freundlich isotherm equation could well describe the adsorption equilibrium behaviors of chlorinated aromatics with r2 from 0.920 to 0.999. The H-bond donor/acceptor group, hydrophobicity, solubility and molecular volume were identified as important solute properties that affect the PAC adsorption capacity. These results could assist water professionals in removing chlorinated aromatics during emergency drinking water treatment.

PAC Addition for MBR Start up in Micro-polluted Water Treatment

In order to improve membrane reactor( MBR) performance for micro-polluted surface water treatment in start-up phase,removals of nitrogen and organic matters especially synthetic organic matters by MBR and a simultaneous application of powdered activated carbon( PAC) with MBR( PAC-MBR) using flat sheet membrane are investigated. The results confirm that MBR treatment can be effective for the removal of organic matters including trace organics. The added PAC can improve contaminant removal efficiency especially in the beginning of operation when MBR cannot effectively remove contaminants and effluent satisfying quality standards is obtained. Moreover,the removal efficiency of target trace synthetic organics is investigated and the removal mechanism is discussed. Biodegradation by microorganism,rejection by filtration of membrane with biofilm and adsorption all contribute to the removal performance. Furthermore,volatile organic compounds can be removed by aeration. The filtration process is confirmed important for natural organic matters( NOM)removal in both MBR and PAC-MBR systems. Combining with PAC,the MBR can remove all fractions of NOM while the single MBR can hardly reduce fulvic or humic acid in water even during the steady operation.

Determination of the Dose of PAC in Ultrafiltration System for Drinking Water Treatment

Immersed ultrafiltration (UF) process was chosen to treat the raw water of the Yangtze River. In order to control the membrane fouling, powdered activated carbon (PAC) was added to the UF tank for removing natural organic matter (NOM). The optimal dosage of PAC was investigated in the PAC/UF combined process. UV254 was used to measure the organic matter adsorbed by PAC. And the results show that the maximum elimination can be achieved while the dosage of PAC is 60mg/L. However, the elimination can not reduce the rate of membrane fouling which indicates that the organic matter absorbed by PAC is not the only factor leading to the fouling and the overload of PAC also contributes to the fouling. Therefore, the optimal dosage of PAC should be determined by organic matter removal as well as membrane fouling control. The ultimately optimized dosing of PAC is 20mg/L in this study, and the average removal rate of the PAC/UF process for dissolved organic carbon (DOC), UV254, and CODMn are 42.6%, 63.4%, and 45.7% respectively.

Rapid removal of bisphenol A on highly ordered mesoporous carbon

Bisphenol A （BPA） is of global concern due to its disruption of endocrine systems and ubiquity in the aquatic environment. It is important, therefore, that efforts are made to remove it from the aqueous phase. A novel adsorbent, mesoporous carbon CMK-3, prepared from hexagonal SBA- 15 mesoporous silica was studied for BPA removal from aqueous phase, and compared with conventional powdered activated carbon （PAC）. Characterization of CMK-3 by transmission electron microscopy （TEM）, X-ray diffraction, and nitrogen adsorption indicated that prepared CMK-3 had an ordered mesoporous structure with a high specific surface area of 920 m^2/g and a pore-size of about 4.9 nm. The adsorption of BPA on CMK-3 followed a pseudo second-order kinetic model. The kinetic constant was 0.00049 g/（mg.min）, much higher than the adsorption of BPA on PAC. The adsorption isotherm fitted slightly better with the Freundlich model than the Langmuir model, and adsorption capacity decreased as temperature increased from 10 to 40℃. No significant influence of pH on adsorption was observed at pH 3 to 9; however, adsorption capacity decreased dramatically from pH 9 to 13.

Cement-based solidification/stabilization of contaminated soils by nitrobenzene

The cement-based solidification/stabilization （S/S） of nitrobenzene （NB） contaminated soils, with cement and lime as binders, sodium silicate solution and powder activated carbon （PAC） as additives, was optimized through an orthogonal experiment, and S/S efficiency was estimated by both leaching test and volatilization measurement. The leaching test results showed that the factors affecting S/S efficiency were NB concentration, cement-to-lime ratio and binder-to-soils ratio, in sequence. With increasing curing time, the leaching concentration of NB between different levels of the same factor in the orthogonal experiment decreased, and less than 9% NB leached out from the 28 d cured samples. The volatilization measurement results indicated that 0.5 %0 of NB was volatilized during the mixing and curing processes for the samples without PAC in the 28 d cycle, whereas adding 2 wt% and 5 wt% PAC, with respect to the weight of contaminated soils, could reduce NB volatilization to half of its original values either during the mixing or curing process. The optimizing formula, that is, contaminated soils （dry weight）：cement：lime = 100：25：25, with 5 wt% additional sodium silicate and 2 wt% additional PAC, was applied to the engineering application of NB contaminated soils. Both the leaching test results of the product and the ambient air quality monitoring results met related regulations during the treating process.

Preparation and characterization of a lipoid adsorption material and its atrazine removal performance

A novel adsorbent named lipold adsorption material （LAM）, with a hydrophoblc nucleolus （trlolem） and a hydrophlllc membrane structure （polyamide）, was synthesized to remove hydrophobic organic chemicals （HOCs） from solution. Triolein, a type of lipoid, was entrapped by the polyamide membrane through an interfacial polymerization reaction. The method of preparation and the structure of the LAM were investigated and subsequent experiments were conducted to determine the characteristics of atrazine （a type of HOC） removal from wastewater using LAM as the adsorbent. The results showed that LAM had a regular structure compared with the prepolymer, where compact particles were linked with each other and openings were present in the structure of the LAM in which the fat drops formed from triolein were entrapped. In contrast to the atrazine adsorption behavior of powdered activated carbon （PAC）, LAM showed a persistent adsorption capacity for atrazine when initial concentrations of 0.57, 1.12, 8.31 and 19.01 mg/L were present, and the equilibrium time was 12 hr. Using an 8 mg/L initial concentration of atrazine as an indicator of HOCs in aqueous solution, experiments on the adsorption capacity of the LAM showed 69.3% removal within 6-12 hr contact time, which was close to the 75.5% removal of atrazine by PAC. Results indicated that LAM has two atrazine removal mechanisms, namely the bioaccumulation of atrazine by the nucleous material and physical adsorption to the LAM membrane. Bioaccumulation was the main removal mechanism.