Effluent Dissolved Organic Carbon Research Articles

Effect of temperature during the hydrothermal carbonization of sewage sludge on the aerobic treatment of the produced process waters

The treatment of the highly contaminated process water produced during the hydrothermal carbonization (HTC) of waste activated sludge is of major concern for the full-scale implementation of the HTC process. So far, no satisfying treatment strategies have been elaborated and the biodegradability under aerobic conditions has hardly been studied. To fill these gaps, aerobic tests were first carried out in batches with HTC process waters produced at 190 °C, 218 °C and 249 °C, and two parallel sequencing batch reactors (SBR) were operated to treat process waters produced at 190 °C and 217 °C. Both experiments show that the HTC temperature has only a little effect on the elimination of dissolved organic carbon (DOC). In the aerobic batch tests, DOC removal were 80.5–81.9 %. In the SBR, 28 % of the initial DOC was found to be recalcitrant, and 25–28 % of the initial nitrogen. In the SBR experiments, the nitrification was also monitored, and nitrification inhibition test were conducted on both process waters obtained at 190 °C and 217 °C. Nitrification the initial SBR reactors was only possible after dilution of the process waters, which indicates the presence of inhibiting substances. The inhibition tests validated those observations, and showed that process waters derived at 217 °C had a higher inhibition potential. This study demonstrates that aerobically treated HTC process waters are still too polluted to be discharged in a wastewater treatment plant: model calculations showed an increase in effluent DOC of 8.3 mg C/L.

The global significance of abiotic factors affecting nitrate removal in woodchip bioreactors

Woodchip bioreactor (WBR) is one of the green infrastructures in the agriculture system to reduce nitrate from agricultural drainage and stormwater. A lot of abiotic factors have been reported that affect nitrate removal lacking a comprehensive understanding. In this study, we studied eight important abiotic factors, including media age, hydraulic retention time (HRT), influent nitrate concentration (Cin), temperature, dissolved organic carbon (DOC), dissolved oxygen (DO), pH, and effective porosity (ρe) of WBR-filling materials. Based on a database that included 10,179 sets of data from 63 peer-reviewed articles, the nitrate removal rate (NRR) and nitrate removal efficiency (NRE) corresponding to the eight abiotic factors by different categories were comprehensively reported. According to this database, this study found the optimal range of abiotic factors for NRR and NRE in WBR were different. Regarding NRR, the optimal range of media age, HRT, Cin, temperature, effluent DOC, DO, pH, and ρe were in the first year, 0–5 h, 10–20 mg L−1, 20–25 °C, 0–5 mg L−1, 0–0.5 mg L−1, 7–8, and 0.6–0.7, respectively. For NRE, the optimal range of media age, HRT, Cin, temperature, effluent DOC, DO, pH, and ρe were in the first year, 500–3000 h, 0–10 mg L−1, 10–15 °C, >50 mg L−1, 0–0.5 mg L−1, 4–5, and 0.4–0.5, respectively. Moreover, the principal component analysis (PCA) indicated the field studies' principal components were different from laboratory studies. Furthermore, the structural equation modeling (SEM) also revealed the causal relationship of the eight abiotic factors on NRR and NRE is totally different. Lessons from this study can be incorporated into DNBR designs, especially improving nitrate removal rates by optimizing different abiotic factors. It also provides insights regarding the contributions of different abiotic factors for NRR and NRE independently and comprehensively.

Nitrate removal and environmental side-effects controlled by hydraulic residence time in woodchip bioreactors treating cold agricultural drainage water

ABSTRACT Denitrifying woodchip bioreactors (WBRs) remove nitrate () from agricultural drainage water at field-scale, but their efficacy at cold temperatures remains uncertain. This study shows how hydraulic residence time (HRT) controls removal and environmental side-effects of WBRs at low water temperature under pilot-scale conditions with controlled operation of nine WBRs (94 dm3). Hydraulic properties were assessed by a bromide tracer test, and removal, emissions of nitrous oxide (N2O) and methane (CH4), and losses of dissolved organic carbon (DOC) were measured at HRTs of 5–30 h. Inlet concentrations were increasingly reduced at higher HRTs. The relationship between HRT and the efficiency (%) of removal was linear ( = 0.94), while the relationship between HRT and reduction rates (NRR) was logistic ( = 0.88). Gaseous emissions of N2O were equally low at HRTs of 10–30 h, but higher at 5 h (P < 0.05). Methane fluxes were small, but with consistent emissions at HRTs of 20–30 h and uptake at 5–15 h. HRT had limited effect on effluent DOC concentrations, but strong effect on mass losses that were five-fold higher (320 mg L−1) at the HRT of 5 h than at 30 h. In summary, at cold temperatures HRTs of ≤ 20 h resulted in suboptimal NRR, accelerating DOC losses, and increased risk of N2O losses at least below a threshold HRT of 5–10 h. HRTs of 20–30 h gave maximal NRR, smallest losses of DOC and N2O, but an increased risk of CH4 emissions.

Evolution of low molecular weight organic compounds during ultrapure water production process: A pilot-scale study

This study evaluated the evolution of low molecular weight organic compounds in ultrapure water (UPW) production using a pilot-scale UPW production system and an ultrafiltration–reverse osmosis (UF–RO) system. During UPW production, a dissolved organic carbon (DOC) removal efficiency of 99.4% was achieved with a feedwater DOC level of 1.42 mg/L. The pretreatment, make-up, and polishing stages accounted for 85.3%, 13.7%, and 0.4% of DOC removal, respectively. Urea, trichloromethane, and dibromochloromethane persisted throughout UPW production process, contributing 24.7%, 9.2%, and 22.6%, respectively, to the final effluent DOC level of 8.1 μg/L. The pretreatment and make-up stages of the UPW production process could remove N-nitrosodimethylamine, chloral hydrate, dichloroacetonitrile, and tribromomethane. The UF–RO system could remove approximately 90% of DOC. However, the proportion of halogenated disinfection by-products (DBPs) in the DOC increased by 1.4–4.5 times in the RO effluents. RO could completely reject haloacetaldehydes. However, RO could not completely remove trichloromethane, tribromomethane, bromodichloromethane, and dibromoacetonitrile, which remained the main halogenated DBPs in the RO effluents.

Comparison of agricultural wastes and synthetic macromolecules as solid carbon source in treating low carbon nitrogen wastewater

This paper investigated the feasibility of using agricultural wastes and synthetic macromolecules as solid carbon sources and studied the effects of improvement of denitrification by the selected agricultural wastes. The carbon release capacity and denitrification performance of corncob (CC), peanut shell (PS), obsolescent rice (OR) and polycaprolactone (PCL), poly butylene succinate (PBS), polyvinyl alcohol sodium alginate (PVA-SA) were systematically analyzed. The results showed that for each carbon source, the first-order kinetic equation was basically followed during the carbon release process. PVA-SA, CC and PS had higher carbon release capacity with accumulative dissolved organic carbon (DOC) of 16.22–20.63 mg·g−1 and chemical oxygen demand (COD) of 100.86–134.10 mg·g−1. Correspondingly, they showed excellent denitrification performance with almost no residual NO3−-N, and the denitrification process well followed the Monod equation. PCL, PBS and OR had lower carbon release capacity with accumulative DOC of 2.06–3.14 mg·g−1 and COD of 13.29–24.13 mg·g−1, respectively. Nevertheless, these materials can also improve the denitrification performance, with the residual NO3−-N in the range of 6.02–6.36 mg·L−1, and the effluent DOC was in the range of 10–15 mg·L−1. Synthetic polymers are more suitable for nitrogen removal in groundwater treatment, while agricultural wastes are ideal carbon sources for secondary effluent treatment.

Preparation and characterization of TiO2 generated from synthetic wastewater using TiCl4 based coagulation/flocculation aided with Ca(OH)2

This study focused on the preparation of undoped and Ca-doped titania from flocculation generated sludge. Initially, TiCl4 was utilised to perform coagulation and flocculation in synthetic wastewater and an optimised dose of coagulant was determined by evaluating the turbidity, dissolved organic carbon (DOC) and zeta potential of the treated water. Later, using Ca(OH)2 as a coagulant aid, the effects on effluent pH, turbidity and DOC removal were investigated. Both Ca-doped and undoped anatase TiO2 were prepared from the flocculated sludge for morphological and photocatalytic evaluation. During the standalone use of TiCl4, maximum turbidity and DOC removal were found at 11.63 and 14.54 mg Ti/L, respectively. At the corresponding coagulant dose, rapid deprotonation of water caused the pH of the effluent to reach below 3.77 mg Ti/L. Whereas, when using Ca(OH)2 as a coagulant aid, a neutral pH (7.26) was attained at a simultaneous dosing of 32.40 mg Ca/L and 14.54 mg Ti/L. When aided with Ca(OH)2, the turbidity removal was further increased by 54.28% and the DOC removal was somewhat similar to the standalone use of TiCl4. TiO2 was prepared by incinerating the collected sludge at 600 °C for 2 h. Both XRD and SEM analysis were conducted to observe the morphology of the prepared titania. The XRD pattern of the TiO2 showed only an anatase phase along with the presence of a high atomic proportion of Ca (4.14%). Consequently, a high amount of Ca atoms inhibited the level of TiO2 phase and no obvious presence of CaO was observed. The prepared Ca-doped TiO2 at the optimised dose of Ca(OH)2 was found to be inferior to the undoped TiO2 during the photodegradation of acetaldehyde. However, a reduced dose of Ca(OH)2 (<15 mg Ca/L) exhibited a substantial increase in photoactivity under UV irradiance.

The importance of sewage effluent discharge in the export of dissolved organic carbon from U.K. rivers

AbstractThe flux of fluvial carbon from the terrestrial biosphere to the world's oceans is known to be an important component of the global carbon cycle, but within this pathway, the flux and return of carbon to the river network via sewage effluent has not been quantified. In this study, monitoring data from 2000 to 2016 for the dissolved organic carbon (DOC) concentration, biochemical oxygen demand, and chemical oxygen demand of the final effluent of sewage treatment works from across England were examined to assess the amount of DOC contributing to national‐scale fluvial fluxes of carbon. The study shows that the median concentration of DOC in final effluent was 9.4 compared with 4.8 mg C/L for all surface waters for the United Kingdom over the study period and that the DOC in final effluent significantly declined over the study period from 11.0 to 6.4 mg C/L. Rivers receiving sewage effluent showed a significant, on average 19%, increase in DOC concentration downstream of sewage discharges. At the scale of the United Kingdom, the flux of DOC in final effluent was 31 ktonnes C/year with a per capita export of 0.55 kg C/year and compared with an average annual flux of DOC from the United Kingdom of 859 ktonnes C/year, that is, only 3.6% of national‐scale flux. The lability of this DOC was limited, with only 7.4% loss of final effluent DOC concentration over in‐stream residence times of up to 5 days. The direct decline in DOC concentration from sewage treatment works was not large enough on its own to explain the declines observed in DOC concentration in U.K. rivers at their tidal limit.

Enhanced DOC removal using anion and cation ion exchange resins

Hardness and DOC removal in a single ion exchange unit operation allows for less infrastructure, is advantageous for process operation and depending on the water source, could enhance anion exchange resin removal of dissolved organic carbon (DOC). Simultaneous application of cationic (Plus) and anionic (MIEX) ion exchange resin in a single contact vessel was tested at pilot and bench scales, under multiple regeneration cycles. Hardness removal correlated with theoretical predictions; where measured hardness was between 88 and 98% of the predicted value. Comparing bench scale DOC removal of solely treating water with MIEX compared to Plus and MIEX treated water showed an enhanced DOC removal, where removal was increased from 0.5 to 1.25 mg/L for the simultaneous resin application compared to solely applying MIEX resin. A full scale MIEX treatment plant (14.5 MGD) reduced raw water DOC from 13.7 mg/L to 4.90 mg/L in the treated effluent at a bed volume (BV) treatment rate of 800, where a parallel operation of a simultaneous MIEX and Plus resin pilot (10 gpm) measured effluent DOC concentrations of no greater than 3.4 mg/L, even at bed volumes of treatment 37.5% greater than the full scale plant. MIEX effluent compared to simultaneous Plus and MIEX effluent resulted in differences in fluorescence intensity that correlated to decreases in DOC concentration. The simultaneous treatment of Plus and MIEX resin produced water with predominantly microbial character, indicating the enhanced DOC removal was principally due to increased removal of terrestrially derived organic matter. The addition of Plus resin to a process train with MIEX resin allows for one treatment process to remove both DOC and hardness, where a single brine waste stream can be sent to sewer at a full-scale plant, completely removing lime chemical addition and sludge waste disposal for precipitative softening processes.

Changes in metal mobility associated with bark beetle-induced tree mortality

Recent large-scale beetle infestations have caused extensive mortality to conifer forests resulting in alterations to dissolved organic carbon (DOC) cycling, which in turn can impact metal mobility through complexation. This study analyzed soil-water samples beneath impacted trees in concert with laboratory flow-through soil column experiments to explore possible impacts of the bark beetle infestation on metal release and transport. The columns mimicked field conditions by introducing pine needle leachate and artificial rainwater through duplicate homogenized soil columns and measuring effluent metal (focusing on Al, Cu, and Zn) and DOC concentrations. All three metals were consistently found in higher concentrations in the effluent of columns receiving pine needle leachate. In both the field and laboratory, aluminum mobility was largely correlated with the hydrophobic fraction of the DOC, while copper had the largest correlation with total DOC concentrations. Geochemical speciation modeling supported the presence of DOC-metal complexes in column experiments. Copper soil water concentrations in field samples supported laboratory column results, as they were almost twice as high under grey phase trees than under red phase trees further signifying the importance of needle drop. Pine needle leachate contained high concentrations of Zn (0.1 mg l(-1)), which led to high effluent zinc concentrations and sorption of zinc to the soil matrix representing a future potential source for release. In support, field soil-water samples underneath beetle-impacted trees where the needles had recently fallen contained approximately 50% more zinc as samples from under beetle-impacted trees that still held their needles. The high concentrations of carbon in the pine needle leachate also led to increased sorption in the soil matrix creating the potential for subsequent carbon release. While unclear if manifested in adjacent surface waters, these results demonstrate an increased potential for Zn, Cu, and Al mobility, along with increased deposition of metals and carbon beneath beetle-impacted trees.

Depth filtration using novel fiber-ball filter media for the treatment of high-turbidity surface water

Performance of the novel fiber-ball filter was investigated for the treatment of high-turbidity surface water. Impact of different operating parameters, such as coagulant type, coagulant dose and filtration velocity on the effluent turbidity, dissolved organic carbon (DOC) and head loss, as well as the particle removal characteristics were studied. The clean-bed filtration results showed that the fiber-ball filters had a great potential for the removal of turbidity matters. Addition of polymeric aluminum ferric chloride (PAFC) enhanced the removal of effluent turbidity and DOC, while the head loss was also increased. The effluent turbidity could be <0.5NTU and the removal efficiency of DOC was ∼16% when the PAFC was dosed at 12mg/L. The effluent turbidity and DOC increased slightly with increasing filtration velocities (30–50m/h) due to the greater drag forces resulted from higher filtration velocities. However, the head loss was also increased. The particle removal characteristics indicated that large particles were primarily removed in the top 30cm of the filter bed and the deep depth in the bottom 20cm played an important role in preventing the occurrence of turbidity breakthrough. It was also found that particles in the size larger than 2μm could be well removed by the fiber-ball filters, implying the potential application for the removal of protozoa like Cryptosporidium (3–15μm) to meet the desired requirement for drinking water treatment during depth filtration.

Behavior and characteristics of DOM during a laboratory-scale horizontal subsurface flow wetland treatment: Effect of DOM derived from leaves and roots

In order to study the effect of dissolved organic matter (DOM) from the leaves and roots of wetland plants on the dissolved organic carbon (DOC) reduction during a laboratory-scale horizontal subsurface flow constructed wetland (HSFW) treatment, excitation–emission matrixces (EEMs) analysis was conducted as a tracer in an effort to understand the biological or physicochemical functioning of this complex environment. Using XAD-8/XAD-4 resins, the DOM in the secondary effluent, HSFW effluent, and the DOM derived from the leaves and roots (DOM L&R) were fractionated into five classes: hydrophobic acid (HPO-A), hydrophobic neutral (HPO-N), transphilic acid (TPI-A), transphilic neutral (TPI-N) and hydrophilic fraction (HPI). DOC was removed by 37.2% during the HSFW treatment. On the other hand, hydrophobic/hydrophilic distribution of the HSFW effluent DOM changed significantly, with the effluent DOC becoming more hydrophobic due to a preferential removal of HPI (with a reduction of 64.8%). Furthermore, the trihalomethane formation potential (THMFP) reduction of the HSFW system was quite low (20.2%), partially being ascribed to the influence of the relatively higher specific THMFP (STHMFP) of the DOM L&R fractions (especially for HPO-A). The soluble microbial by-products (SMPs) and aromatic protein-like materials (polyphenols) from the leaves and roots could be the main reason for the increased STHMFP of the HSFW effluent DOM fractions. In addition, the peak of Region II ( λ ex/ λ em = (220–260)/(332–380)) might serve as a proxy for monitoring the DOM L&R (polyphenols) in the effluent from a matured wetland.

Saline sewage treatment using a submerged anaerobic membrane reactor (SAMBR): Effects of activated carbon addition and biogas-sparging time

This study investigated the performance of a submerged anaerobic membrane reactor (SAMBR) treating saline sewage under fluctuating concentrations of salinity (0–35 g NaCl/L), at 8 and 20 h HRT, with fluxes ranging from 5–8 litres per square metre per hour (LMH). The SAMBRs attained a 99% removal of Dissolved Organic Carbon (DOC) with 35 g NaCl/L, while removal inside the reactor was significantly lower (40–60% DOC). Even with a sudden drop in salinity overall removal recovered quickly, while the recovery inside the reactor took place at a slower rate. This highlights the positive effect of the membrane in preventing the presence of high molecular weight organics in the effluent while also retaining biomass inside the reactor so that they can rapidly acclimatize to salinity. The reduction of continuous biogas sparging to intervals of 10 min ON and 5 min OFF resulted in a slight increase in transmembrane pressure (TMP) by 0.025 bar, but also resulted in an increase in effluent DOC removal and inside the SAMBR by 10% and 20%, respectively. The addition of powdered activated carbon (PAC) resulted in a decrease in the TMP by 0.070 bar, and an increase in DOC removal in the reactor and effluent by 30% and 5%, respectively. The PAC dramatically decreased the high molecular weight organics in the reactor over a period of 72 h. SEM pictures of the membrane and biomass before and after addition of PAC revealed a remarkable reduction of flocks on the membrane surface, and a reduction inside the reactor of soluble microbial products (SMPs). Finally, Energy Dispersive X-ray (EDX) analysis of the membranes pores and biofilm highlighted the absence of organic matter in the inner pores of the membrane.

Comparison of Dissolved-Organic-Carbon Residuals from Air- and Pure-Oxygen-Activated-Sludge Sequencing-Batch Reactors

Literature shows that full-scale pure-oxygen activated sludge (O2-AS) wastewater treatment plants (WWTPs) generate effluents with higher dissolved-organic carbon (DOC) concentrations and larger high-molecular-weight fractions compared to air-activated-sludge (Air-AS) WWTP effluents. The purpose of this paper was to evaluate how gas supplied (air vs. pure oxygen) to sequencing-batch reactors affected DOC transformations. The main conclusions of this paper are (a) O2-AS effluent DOC is more refractory than air-AS effluent DOC; and (b) O2-AS systems may have higher five-day biochemical oxygen demand removals than air-AS systems; however, in terms of COD and DOC removal, air-AS systems are better than O2-AS systems. Analysis of a database from side-by-side O2- and air-AS pilot tests from literature supported these observations.

Transformation of Molecular Weight Distributions of Dissolved Organic Carbon and UV‐Absorbing Compounds at Full‐Scale Wastewater‐Treatment Plants

The molecular-weight distribution (MWD) of wastewater dissolved-organic carbon (DOC) was determined in samples from seven full-scale wastewater-treatment plants (WWTPs) that use different biological treatments (air activated sludge [air-AS], pure-oxygen AS [O2-AS], and trickling filters). The research objective was to determine how different biological treatments influenced the MWD of wastewater DOC. Primary sedimentation effluent DOC from most of the WWTPs exhibited a skewed distribution toward the low-molecular-weight fraction (MWF) (40 to 50%, < 0.5 K Daltons [KDa]). The Air-AS effluent DOC exhibited a centrally clustered distribution, with the majority of DOC in the intermediate MWF (0.5 to 3 KDa). The O2-AS effluent DOC exhibited a skewed distribution toward the high MWF (> 3 KDa). The removal of DOC by air- and O2-AS bacteria followed trends predicted by a macromolecule degradation model. Trickling-filter effluent DOC exhibited a skewed distribution toward the high MWF (50% DOC, > 3 KDa).

Speciation of copper in sewage effluents and its toxicity to Daphnia magna

Copper complexation capacity was determined in a range of sewage treatment works final effluents and receiving waters, upstream and downstream of the discharge point. Forty-eight-hour immobilization tests on Daphnia magna were used to assess the toxicity of copper in the effluent matrix. Complexation capacities in effluents were typically in the range 50 to 100 microg Cu/L, with higher values being found in the poorer-quality effluents with higher dissolved organic carbon (DOC) concentrations. The tolerance of Daphnia to dissolved copper concentrations was more than quadrupled in a 50% effluent matrix, with the increase in tolerance being related to complexation capacity. Ligand concentrations in effluents were found to correlate strongly with effluent DOC. No such relationship was observed in surface waters. On mixing with river water, sewage-derived ligands behaved conservatively and were relatively stable over time scales of up to 10 d.

The importance of soluble microbial products (SMPs) in biological drinking water treatment

The formation of soluble microbial products (SMPs) during a drinking water ozone-biofiltration process was estimated using two approaches. First, a model was developed that related the assimilation of biodegradable organic matter (BOM) to the accumulation of biomass on filter media. The model was calibrated with data from a regularly backwashed, pilot scale biofilter that approximated a steady-state plug flow reactor. The second approach was a direct measurement of SMP concentrations, accomplished by applying a synthetic water comprised of known compounds to a bio-acclimated filter. The SMP concentration was estimated by determining the difference between known-compound removal (on a carbon basis) and dissolved organic carbon (DOC) removal. Comparable results were obtained from both approaches. SMPs were found to be important relative to the carbon removal that is typically measured (DOC), indicating that this measurement can significantly underestimate the actual BOM removal (17–33% in this research). The concentration of SMPs was negligible relative to the filter effluent DOC pool.

Dissolved organic carbon transformations during laboratory-scale groundwater recharge using lagoon-treated wastewater

Reuse of treated wastewater through groundwater recharge has emerged as an integral part of water and wastewater management in arid regions of the world. Aerated-lagoon wastewater treatment followed by surface infiltration offers a simple low-tech, low-cost treatment option for developing countries. This study investigated the fate of dissolved organic carbon (DOC) through laboratory-scale soil aquifer treatment (SAT) soil columns over a 64-week period. Aerated-lagoon wastewater (average DOC=17 mg/l) and two soils were collected near the USA/Mexico border near Nogales, AZ. Laboratory-scale SAT columns exhibited three phases of ‘aging' where infiltration rates and DOC removals were delineated. DOC removal ranged from 39% to greater than 70% during the study, with DOC levels averaging 3.7 and 5.8 mg/l for the SAT columns packed with different soils. Soil with a higher fraction of organic carbon content had higher effluent DOC levels, presumably due to leaching of soil organic matter. UV absorbance data indicated preferential biodegradation removal of low molecular weight, low aromatic DOC. Overall, SAT reduced the potential towards forming trihalomethanes (THMs) during disinfection, although the reactivity (μg THM/mg DOC) increased. SAT and groundwater recharge would provide a high degree of DOC removal in an integrated low-tech wastewater reuse management strategy, especially for developing countries in arid regions of the world.

Desorption controlled mobility and intrinsic biodegradation of anthracene in unsaturated soil

Desorption, sorption and biodegradation control the fate of polycyclic aromatic hydrocarbons (PAH) in contaminated soils. The interaction of these processes was studied in a two-layer column experiment with uncontaminated and spiked A-horizon material (13C anthracene) at unsaturated water flow conditions. During constant irrigation (part I of the experiment) the development of a stationary effluent composition was observed. The onset of anthracene breakthrough was delayed by 350 pore volumes (pvs) indicating high affinity sorption towards soil organic matter. The coincidence of anthracene breakthrough with increasing dissolved organic carbon (DOC) concentrations pointed to a carrier-mediated transport of the contaminant. Flow interruptions of varied duration (part II of the experiment) yielded a pronounced response of solution phase parameters. Effluent DOC increased linearly with time of flow interruption, indicating a zero-order rate-limited release. In contrast, anthracene concentrations showed a sharp drop after the stopped-flow events. Thus, the effluent anthracene concentration observed in part I may have been controlled by rate-limited sorption in the uncontaminated layer. Biodegradation of anthracene was evident from 13C-labelled metabolites and the complete decline of effluent anthracene after 1400 pvs. Although PAH seepage in soils is enhanced by rate-limited sorption it may be effectively counteracted by microbial activity.

Pilot plant study on ozonation and biological activated carbon process for drinking water treatment

A study on advanced drinking water treatment was conducted in a pilot scale plant taking raw water from Minaga Reservoir, Japan. Ozonation-biological activated carbon process (O3-BAC), BAC process (BAC) and chlorination-granular activated carbon adsorption process (Cl2-GAC) were evaluated based on the following parameters; dissolved organic carbon (DOC), adsorbable DOC (ADOC) and biodegradable DOC (BDOC). The raw water used was pre-treated by biofiltration for suspended solid removal and biological treatment. Contact time for ozonation and chlorination was 24 min. Empty bed contact time of activated carbon column was 15 min. Ozone dosage was 3 mg • 1−1. Chlorination was carried out to maintain a residual chlorine concentration of 0.2 mg • 1−1. Effluent DOC from biofiltration consisted of mainly ADOC (90%) and BDOC (10%). Therefore, DOC was mainly removed by adsorption in all processes. However, biodegradable DOC increased by 20% after ozonation in O3-BAC and was removed effectively by the attached bacteria on the activated carbon. Significant differences in DOC removal were not noted among the three processes during 8 months of operation. After the saturation of activated carbon, the effluent DOC from the O3-BAC was lower than that from BAC and Cl2-GAC. Ozonation improved biodegradability of organic substances and effluent water quality by the following biodegradation of biodegradable DOC by biological activated carbon.

Pilot plant study on ozonation and biological activated carbon process for drinking water treatment

A study on advanced drinking water treatment was conducted in a pilot scale plant taking raw water from Minaga Reservoir, Japan. Ozonation-biological activated carbon process (O3-BAC), BAC process (BAC) and chlorination-granular activated carbon adsorption process (Cl2-GAC) were evaluated based on the following parameters; dissolved organic carbon (DOC), adsorbable DOC (ADOC) and biodegradable DOC (BDOC). The raw water used was pre-treated by biofiltration for suspended solid removal and biological treatment. Contact time for ozonation and chlorination was 24 min. Empty bed contact time of activated carbon column was 15 min. Ozone dosage was 3 mg · 1-1. Chlorination was carried out to maintain a residual chlorine concentration of 0.2 mg · 1-1. Effluent DOC from biofltration consisted of mainly ADOC (90%) and BDOC (10%). Therefore, DOC was mainly removed by adsorption in all processes. However, biodegradable DOC increased by 20% after ozonation in 03-BAC and was removed effectively by the attached bacteria on the activated carbon. Significant differences in DOC removal were not noted among the three processes during 8 months of operation. After the saturation of activated carbon, the effluent DOC from the 03-BAC was lower than that from BAC and Cl2-GAC. Ozonation improved biodegradability of organic substances and effluent water quality by the following biodegradation of biodegradable DOC by biological activated carbon.