Evaluation of an integrated sponge--granular activated carbon fluidized bed bioreactor for treating primary treated sewage effluent

An integrated fluidized bed bioreactor (iFBBR) was designed to incorporate an aerobic sponge FBBR (ASB-FBBR) into an anoxic granular activated carbon FBBR (GAC-FBBR). This iFBBR was operated with and without adding a new starch based flocculant (NSBF) to treat synthetic primary treated sewage effluent (PTSE). The NSBF contains starch based cationic flocculants and trace nutrients. The results indicate that the iFBBR with NSBF addition could remove more than 93% dissolved organic carbon (DOC), 61% total nitrogen (T-N) and 60% total phosphorus (T-P) at just a very short hydraulic retention time of 50 min. The optimum frequency of adding NSBF to the iFFBR is four times per day. As a pretreatment to microfiltration, the iFFBR could increase 5 L/m² h of critical flux thus reducing the membrane fouling. In addition, better microbial activity was also observed with high DO consumption (>66%) and specific oxygen uptake rate (>35 mg O₂/g VSS h).     

Assessment of bacterial growth and total organic carbon removal on granular activated carbon contactors.

The overall growth rate of bacteria on granular activated carbon (GAC) contactors at the Philadelphia Torresdale Water Treatment Pilot Plant facility was found to decrease until steady state was reached. The growth rate was found to fluctuate between 6.94 X 10(-3) and 8.68 X 10(-4) doublings per h. The microbiological removal of total organic carbon (TOC) was calculated by considering the GAC contactors as semiclosed continuous culture systems and using growth yield factors determined in laboratory experiments. After ozonation, the average TOC entering the contactors was 1,488 micrograms/liter, and the average effluent TOC was 497 micrograms/liter. Microbiological TOC removal was found to average 240 micrograms/liter on GAC contactors, which was not significantly different from microbiological TOC (220 micrograms/liter) removal across a parallel sand contactor where no adsorption took place. Thus, GAC did not appear to enhance biological TOC removal. Bacterial growth and maintenance was responsible for approximately 24% of the TOC removal on GAC under the conditions of this study.     

Bioadsorption of lead(II) from aqueous solution by fungal biomass of Aspergillus niger

The removal of lead by waste fungal biomass of Aspergillus niger, originated from citric acid fermentation industry, was investigated. The experimental results indicated that the bioadsorption achieved equilibrium within 4 h. The kinetic analysis of lead adsorption onto the fungal biomass revealed that the bioadsorption process followed the first-order reaction kinetics. The adsorption isotherm can be simulated by Freundlich model, which gave a correlation coefficient equal to 0.93. The lead-loaded biomass can be effectively regenerated by 0.1 M nitric acid. This research demonstrated that the waste biomass of A. niger is a potential bioadsorbent for the removal of lead from aqueous solution.     

Physico-chemical method for ammonia removal from synthetic wastewater using limestone and GAC in batch and column studies

The purpose of the present study was to examine the removal of ammoniacal nitrogen (NH4-N) from synthetic wastewater using limestone (LS) and granular activated carbon (GAC) mixture as low cost adsorbent. In batch study, optimum shaking and settling times were 150 and 120 min, respectively. The LS-GAC mixture ratio of 25:15 removed about 58% NH4-N. The smaller particle size of medium yielded higher adsorption capacity. The equilibrium adsorption data followed the Freundlich isotherm (R2 > 0.98) but it showed weak bond. Adsorption kinetics were well described by the pseudo second-order rate model (R2 > 0.93). The upflow column showed that higher flow rate and initial concentration resulted in shorter column saturation time. The study showed that the usage of GAC could be reduced by combining GAC with LS for the removal of NH4-N from wastewater; thus reducing the cost of treatment.     

Post treatment of groundwater denitrification fluidized bed reactor effluents to achieve drinking water quality

Post treatment of effluents from heterotrophic groundwater denitrification fluidized bed reactors (FBR) designed to achieve drinking water quality has been investigated. The denitrification process adds to the dissolved organic compounds, biomass and bacteria in the effluent. They are also lacking dissolved oxygen. Effluents from the process were treated in combined post treatment processes based on either a trickling filter and sedimentation unit (‘TF combination’) or contact flocculation (‘CF combination’). Both processes were followed by sand filtration, granular activated carbon (GAC) and chlorination. Results regarding total suspended solids (TSS) and turbidity removal showed an advantage to the ‘CF combination’, and the target turbidity (NTU <1) was always achieved when the alum dose was 10 or 20 mg l⁻¹. Backwash of the sand filter and GAC column was required after 27 h of operation (average value). An average total reduction in dissolved organic carbon (DOC) of 40% was observed with a final DOC of 3.5–4 mg L⁻¹. Most of the removal of the DOC occurred in the sand filter (28%), while the GAC contribution was smaller (18%). No regrowth potential was observed using the Werner method when a pure culture of Pseudomonas fluorescens P17 was used as inoculum in samples of chlorinated effluent (post chlorination). When a mixed culture of indigenous bacteria was used as inoculum, a high regrowth potential was observed. Installing an additional chlorination unit before the sand filter column (pre and post chlorination) resulted in effluent with no regrowth potential for both Pseudomonas fluorescens P17 and indigenous bacteria. Received 17 October 1997/ Accepted in revised form 29 May 1998     

Adsorptive removal of Pb(II) by activated carbon prepared from Spartina alterniflora: Equilibrium,kinetics and thermodynamics

Low-cost activated carbon was prepared from Spartina alterniflora by phosphoric acid activation for the removal of Pb(II) from dilute aqueous solution. The effect of experimental parameters such as pH, initial concentration, contact time and temperature on the adsorption was studied. The obtained data were fitted with the Langmuir and Freundlich equations to describe the equilibrium isotherms. The kinetic data were fitted with the Lagergren-first-order, pseudo-second-order and Elovich models. It was found that pH played a major role in the adsorption process. The maximum adsorption capacity for Pb(II) on S. alterniflora activated carbon (SAAC) calculated from Langmuir isotherm was more than 99 mg g⁻¹. The optimum pH range for the removal of Pb(II) was 4.8–5.6. The Freundlich isotherm model was found to best describe the experimental data. The kinetic rates were best fitted to the pseudo-second-order model. Thermodynamic study showed the adsorption was a spontaneous exothermic process.     

Effect of type of granular activated carbon on DOC biodegradation in biological activated carbon filters

The purpose of this paper is to clarify the effect of the two different GAC types (steam activated or chemically activated) on DOC biodegradation in biological activated carbon (BAC) columns. For this purpose, raw water taken from a surface reservoir was fed to continuous-flow lab-scale biofiltration columns which were run for more than 18,000 bed volumes. The effect of pre-ozonation on DOC removal was also evaluated. Experimental results showed that biological activity inside the BAC columns extended the service life and the choice of filter material was crucial in BAC systems. The DOC biodegradation was higher in thermally activated carbon columns compared to the chemically activated one. The ability of GAC to better adsorb and retain organic compounds increased the chance of biodegradation. Contrary to expectations, pre-ozonation did not significantly enhance DOC biodegradation. Despite the high increase in biodegradable dissolved organic carbon (BDOC) upon ozonation, overall DOC biodegradation efficiencies did not differ from raw water. Overall, the DOC biodegradation in columns was higher than in most of the studies. This observation was primarily attributed to the low specific ultraviolet absorption (SUVA) values in raw water indicating a high biodegradability.     

Comparison of activated carbon and bottom ash for removal of reactive dye from aqueous solution

The adsorption of reactive dye from synthetic aqueous solution onto granular activated carbon (GAC) and coal-based bottom ash (CBBA) were studied under the same experimental conditions. As an alternative to GAC, CBBA was used as adsorbent for dye removal from aqueous solution. The amount of Vertigo Navy Marine (VNM) adsorbed onto CBBA was lower compared with GAC at equilibrium and dye adsorption capacity increased from 0.71 to 3.82 mg g(-1), and 0.73 to 6.35 mg g(-1) with the initial concentration of dye from 25 to 300 mg l(-1), respectively. The initial dye uptake of CBBA was not so rapid as in the case of GAC and the dye uptake was slow and gradually attained equilibrium.     

Adsorption of fluorobenzene onto granular activated carbon: isotherm and bioavailability studies

The adsorption of a recalcitrant fluoroaromatic compound, fluorobenzene (FB), onto granular activated carbon (GAC) was evaluated. The respective isotherm was obtained and the Langmuir, Freundlich and Redlich-Peterson models were fitted to the experimental data, with the Redlich-Peterson model giving the best fitting. Freundlich model also provided a good fit but the Langmuir model could not adequately fit the experimental data, especially at high FB concentrations. Maximal adsorption capacity of FB onto GAC was found to be 388mg of FB per gram of GAC. The reversibility of the adsorption of FB onto GAC was investigated, both in the absence and presence of microorganisms. Abiotic desorption of FB occurred to a small extent (between 3% and 22%, for amounts of FB initially adsorbed to the GAC between 37 and 388mgg(-1)), and bioregeneration of GAC was shown to occur when the matrix was exposed to a FB degrading culture, with 58-80% of the adsorbed FB being biodegraded. A residual amount of FB showed not to be bioavailable, suggesting that part of the adsorbed FB may be irreversibly bound. The fraction of the non-bioavailable FB increased at higher amounts of adsorbed FB, from 19% to 33%. The results indicate that the GAC employed in this study has a good capacity to adsorb FB and that bioregeneration of this matrix is a feasible process.     

Study on the removal of pesticide in agricultural run off by granular activated carbon

In this batch study, the adsorption of malathion by using granular activated carbon with different parameters due to the particle size, dosage of carbons, as well as the initial concentration of malathion was investigated. Batch tests were carried out to determine the potential and the effectiveness of granular activated carbon (GAC) in removal of pesticide in agricultural run off. The granular activated carbon; coconut shell and palm shells were used and analyzed as the adsorbent material. The Langmuir and Freundlich adsorption isotherms models were applied to describe the characteristics of adsorption behavior. Equilibrium data fitted well with the Langmuir model and Freundlich model with maximum adsorption capacity of 909.1 mg/g. The results indicate that the GAC could be used to effectively adsorb pesticide (malathion) from agricultural runoff.     

Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge

Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600 °C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity.     

Measurement of biocolloid collision efficiencies for granular activated carbon by use of a two-layer filtration model

Point-of-use filters containing granular activated carbon (GAC) are an effective method for removing certain chemicals from water, but their ability to remove bacteria and viruses has been relatively untested. Collision efficiencies (alpha) were determined using clean-bed filtration theory for two bacteria (Raoutella terrigena 33257 and Escherichia coli 25922), a bacteriophage (MS2), and latex microspheres for four GAC samples. These GAC samples had particle size distributions that were bimodal, but only a single particle diameter can be used in the filtration equation. Therefore, consistent with previous reports, we used a particle diameter based on the smallest diameter of the particles (derived from the projected areas of 10% of the smallest particles). The bacterial collision efficiencies calculated using the filtration model were high (0.8 < or = alpha < or = 4.9), indicating that GAC was an effective capture material. Collision efficiencies greater than unity reflect an underestimation of the collision frequency, likely as a result of particle roughness and wide GAC size distributions. The collision efficiencies for microspheres (0.7 < or = alpha < or = 3.5) were similar to those obtained for bacteria, suggesting that the microspheres were a reasonable surrogate for the bacteria. The bacteriophage collision efficiencies ranged from > or = 0.2 to < or = 0.4. The predicted levels of removal for 1-cm-thick carbon beds ranged from 0.8 to 3 log for the bacteria and from 0.3 to 1.0 log for the phage. These tests demonstrated that GAC can be an effective material for removal of bacteria and phage and that GAC particle size is a more important factor than relative stickiness for effective particle removal.     

Dissolved organic carbon fluxes in the Shetucket River of eastern Connecticut,U.S.A.*

SUMMARY. Seasonal changes in dissolved organic carbon (DOC) concentrations were monitored biweekly for 1 year at seven stations in the Shetucket River watershed in eastern Connecticut, U.S.A. Nine monthly diurnal studies revealed 24-h fluctuations of up to 53% of the seasonal range of 250–2200 μm DOC. Net DOC removal along a 1.9-km stretch below a secondary sewage treatment plant (activated sludge effluent diluted to a final average volume of 1.4% in the river) ranged from 0 to 1600 and averaged 68 ± 64 mmol m^?2 day^?1. Removal of DOC further downstream could only be observed during a severe 3-h October storm when net uptake ranged from 16 to 92 mmol m^?2 h^?1, using upstream-downstream techniques. Oxygen respiration could account for about half of the net DOC removal during the October storm. Even though net uptake was somewhat greater than reported in other lotic studies, about 97% of the DOC potentially available to benthic heterotrophs was exported further downstream.     

Use of jute processing wastes for treatment of wastewater contaminated with dye and other organics

A study was conducted to examine the potential of jute processing waste (JPW) for the treatment of wastewater contaminated with dye and other organics generated from various activities associated with jute cultivation and fibre production. Adsorption studies in batch mode have been conducted using dye solution as an adsorbate and JPW as an adsorbent. A comparative adsorption study was made with standard adsorbents such as powdered and granular activated carbon (PAC and GAC, respectively). A maximum removal of 81.7% was obtained with methylene blue dye using JPW as compared to 61% using PAC and 40% using GAC under similar conditions. The adsorption potential of JPW was observed to be dependent on various parameters such as type of dye, initial dye concentration, pH and dosage of adsorbent. The batch sorption data conformed well to the Langmuir and Freundlich isotherms. However, lower BOD (33.3%) and COD (13.8%) removal from retting effluent was observed using JPW as compared to 75.6% BOD removal and 71.1% COD removal obtained with GAC.     

Removal of H(2)S by Thiobacillus denitrificans immobilized on different matrices

Biological removal of high concentrations of H(2)S was studied using the immobilized Thiobacillus denitrificans with peat moss, wood chip, ceramic and granular activated carbon (GAC) separately. Experiments on the physical adsorption capacity of matrix, retention time and pressure drop were carried out; the ability of bioreactor to buffer shock loading and the removal efficiency with different packing materials were also investigated. Besides, the kinetics of single-stage biodesulfuration was analyzed. The results showed that GAC provided higher bacteria adsorption capacity, showed a more resistance to shock loading and allowed better operational control with respect to pressure drop than other inert carriers. When the retention time was changed from 30 to 100 s at an influent concentration of 100 mg/L of H(2)S, the removal efficiencies were above 98%; when the inlet concentration of H(2)S were changed from 110 to 120 mg/L, an average 96.8% removal efficiency was achieved during the long-term operation for GAC bioreactor. Next to GAC, wood chip was found to be a good packing material; however, peat moss and ceramic had limited effectiveness and their removal efficiencies were less of 90%. The kinetic analysis showed that the maximum removal rate and the half-saturation constant of the GAC bioreactor were 666.7 mg (H(2)S)/(L.d) and 20.8 mg/L, respectively.     

Removal of high concentration of NH3 and coexistent H2S by biological activated carbon (BAC) biotrickling filter

High efficiency of NH3 and H2S removal from waste gases was achieved by the biotrickling filter. Granular activated carbon (GAC), inoculated with Arthrobacter oxydans CH8 for NH3 removal and Pseudomonas putida CH11 for H2S removal, was used as packing material. Under conditions in which 100% H2S was removed, extensive tests to eliminate high concentrations of NH3 emission-including removal characteristics, removal efficiency, and removal capacity of the system-were performed. The results of the Bed Depth Service Time (BDST) experiment suggested that physical adsorption of NH3 gas by GAC was responsible for the first 10 days, after which NH3 gas was biodegraded by inoculated microorganisms. The dynamic steady state between physical adsorption and biodegradation was about two weeks. After the system achieved equilibrium, the BAC biotrickling filter exhibited high adaptation to shock loading, elevated temperature, and flow rate. Greater than 96% removal efficiency for NH3 was achieved during the 140-day operating period when inlet H2S loading was maintained at 6.25 g-S/m3/h. During the operating period, the pH varied between 6.5 and 8.0 after the physical adsorption stage, and no acidification or alkalinity was observed. The results also demonstrated that NH3 removal was not affected by the coexistence of H2S while gas retention time was the key factor in system performance. The retention time of at least 65 s is required to obtain a greater than 95% NH3 removal efficiency. The critical loading of NH3 for the system was 4.2 g-N/m3/h, and the maximal loading was 16.2 g-N/m3/h. The results of this study could be used as a guide for further design and operation of industrial-scale systems.     

Adsorption of Antimony on Sediments from Typical Water Systems in China: A Comparison of Sb(III) and Sb(V) Pattern

The present work investigated the adsorption of Sb(III) and Sb(V) on five sediment samples (Pearl River, Yangtze River, Yellow River, Yongding River, and Liao River) from typical water systems in China and the adsorption of Sb(V) on Pearl River sediment with different organic carbon (OC) fractions using batch experiments. In order to assess the contributions of sedimentary organic components to the overall adsorption of pentavalent Sb on sediments, one sediment sample was treated by commonly used chemical and physical methods to remove different organic components. Experimental data of Sb(III) and Sb(V) adsorption on five sediments were successfully modeled using the Freundlich (r² > 0.96) isotherm. In general, the sediments with high Fe and Al oxide contents and total organic carbon (TOC) had higher Sb(III) and Sb(V) adsorption than the sediments containing small amounts of Fe and Al oxides and TOC. Dissolved organic carbon (DOC) in sediment promoted the adsorption of Sb(V), and humin fractions and black carbon-like material in sediment had a high affinity for Sb(V).     

Activated carbon prepared from biomass as adsorbent: elimination of Ni(II) from aqueous solution.

Activated carbon (AC) prepared from waste Parthenium was used to eliminate Ni(lI) from aqueous solution by adsorption. Batch mode adsorption experiments are carried out, by varying contact time, metal ion concentration, carbon concentration, pH and desorption to assess kinetic and equilibrium parameters. They allowed initial adsorption coefficient, adsorption rate constant and maximum adsorption capacities to be computed. The adsorption data were modeled by using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacity (Q0) calculated from the Langmuir isotherm was 54.35 mg Ni(II)/g of AC at initial pH of 5.0 and 20 degrees C, for the particle size 250-500 microm. Increase in pH from 2 to 10 increased percent removal of metal ion. The regeneration by HCl of Ni(II)-saturated carbon by HCl, allowed suggestion of an adsorption mechanism by ion-exchange between metal ion and H+ ions on the AC surfaces. Quantitative recovery of Ni(II) was possible with HCl.     

Characterization of mesoporous activated carbons prepared by pyrolysis of sewage sludge with pyrolusite

Activated carbons were prepared from sewage sludge by chemical activation. Pyrolusite was added as a catalyst during activation and carbonization. The influence of the mineral addition on the properties of the activated carbons produced was evaluated. The results show that activated carbons from pyrolusite-supplemented sewage sludge had up to a 75% higher BET surface area and up to a 66% increase in mesoporosity over ordinary sludge-based activated carbons. Batch adsorption experiments applying the prepared adsorbents to synthetic dye wastewater treatment yielded adsorption data well fitted to the Langmuir isotherm. The adsorbents from pyrolusite-supplemented sludges performed better in dye removal than those without mineral addition, with the carbon from pyrolusite-augmented sludge T2 presenting a significant increase in maximum adsorption capacity of 50 mg/g. The properties of the adsorbents were improved during pyrolusite-catalyzed pyrolysis via enhancement of mesopore production, thus the mesopore channels may provide fast mass transfer for large molecules like dyes.     

Changes of biomass and bacterial communities in biological activated carbon filters for drinking water treatment

Biological activated carbon (BAC) filtration can usually perform well in removal of biodegradable organic compounds in drinking waters. In this study, a pilot-scale down-flow BAC filtration system was constructed for treatment of ozonated waters. The changes of biomass concentration and bacterial community in the BAC filters with contact time and service time were characterized using phospholipid fatty acid (PLFA) analysis and 16S rRNA gene clone library analysis, respectively. The operational results indicated the BAC filtration system could effectively remove dissolved organic carbon (DOC) and assimilable organic carbon (AOC). Biomass concentration decreased with contact time, but showed only a slight change with service time. Contact time and service time could affect the microbial community structure. Alphaproteobacteria was the largest bacterial group and might have important links with the DOC and AOC removal. This work might provide some new insights into microbial community and biological process in the drinking water biofilters.