Dissolved Organic Carbon Reduction Research Articles

Assessing RBF reduction/removal mechanisms for microbial and organic DBP precursors

Significant reductions/removals of selected microorganisms and disinfection by‐products as defined by dissolved organic carbon (DOC) were observed in four riverbank filtration (RBF) facilities. The objective of this study was to quantify the contributions of subsurface filtration (or underground passage) and groundwater dilution to overall RBF reductions/removals. The microbes quantified included aerobic spore‐forming bacteria, total coliforms, Escherichia coli, and male‐specific bacteriophage. Both groundwater dilution and subsurface filtration appeared to be important reduction/removal processes but subsurface filtration was considered most influential with regard to microbial reductions. The relative importance of subsurface filtration removals may be a function of RBF site characteristics, especially travel time and distance between the river and the RBF extraction well. Complete removals were observed for all microorganisms except virus indicators, which were considered the most problematic. The significant DOC reductions observed were attributed to dilution, biodegradation, and adsorption reduction/removal mechanisms. The relative contribution of each mechanism was site‐specific.

Comparative study of ozonation and synthetic goethite-catalyzed ozonation of individual NOM fractions isolated and fractionated from a filtered river water

This study comparatively investigated ozonation and synthetic goethite-catalyzed ozonation of individual natural organic matter (NOM) fractions in terms of ozone consumption, dissolved organic carbon (DOC) and UV-absorbance reduction, molecular weight (MW) distribution, and formation of low-MW oxidation by-products. Hydrophobic acid and neutral (HOA and HON) and hydrophilic acid and base (HIA and HIB) were four major NOM fractions isolated from a filtered river water; so ozonation and catalytic ozonation were carried out on these fractions. Results indicate that in comparison to ozonation alone, catalytic ozonation can enhance ozone consumption, UV 254 and DOC reduction, fragmentation of fraction components with MW>3000 Da, and formation of oxalic acid for these fractions under normal reaction conditions commonly adopted in water treatment plants. In addition, catalytic ozonation can enhance aldehydes formation and increase the percentage of easy biodegradable organic carbon compared with ozonation alone for HIA and HIB, but exert much less effect on these items for HOA and HON.

Reduction of dissolved organic matter in terms of DOC, UV-254, SUVA and THMFP in industrial estate wastewater treated by stabilization ponds

The aim of this research was to monitor the influent and effluent water quality of the aeration, facultative and oxidation water treatment ponds of an industrial estate. This industrial estate, the largest in northern Thailand, has proposed to utilization of reclaimed treated wastewater in their raw water supply so as to cope with the yearly water shortage during the dry season. Water samples were collected four times from four sampling points and evaluated for their dissolved organic matter (DOM) content in terms of dissolved organic carbon (DOC), ultraviolet light absorbance at 254 nm (UV-254), specific ultraviolet absorption (SUVA), trihalomethane formation potential (THMFP) and trihalomethane (THM) species. Average values of DOC, UV-254, SUVA and THMFP in the influent wastewater of 12.9 mg L(-1), 0.165 cm(-1), 1.29 L mg(-1) m(-1) and 1.24 mg L(-1), respectively, were observed. The aeration ponds produced the best results: a 54% reduction of DOC, a 33% reduction of UV-254, and a 57% reduction of THMFP. However, SUVA in the aeration pond effluent showed a moderate increase. The facultative ponds and oxidation ponds did not take part in the reduction of DOC, UV-254, SUVA and THMFP. Average DOC, UV-254, SUVA and THMFP value of the treated wastewater were 5.8 mg L(-1), 0.107 cm(-1), 1.85 L mg(-1) m(-1) and 468 microg L(-1), respectively. Chloroform, at 72.6% of total THMFP, was found to be the predominant THM species.

A field study of advanced municipal wastewater treatment technology for artificial groundwater recharge

Field studies were conducted to investigate the advanced treatment of the municipal secondary effluent and a subsequent artificial groundwater recharge at Gaobeidian Wastewater Treatment Plant, Beijing. To improve the secondary effluent quality, the combined process of powdered activated carbon adsorption, flocculation and rapid sand filtration was applied, which could remove about 40% dissolved organic carbon (DOC) and 70% adsorbable organic halogens. The results of liquid size exclusion chromatography indicate that in the adsorption unit the removed organic fraction was mainly low molecular weight compounds. The fractions removed by the flocculation unit were polysaccharides and high molecular weight compounds. The retention of water in summer in the open recharge basins resulted in a growth of algae. Consequently, DOC increased in the polysaccharide and high molecular weight humic substances fraction. The majority of the DOC removal during soil passage took place in the unsaturated area. A limited reduction of DOC was observed in the aquifer zone.

An investigation into reservoir NOM reduction by UV photolysis and advanced oxidation processes

A comparison of four treatment technologies for reduction of natural organic matter (NOM) in a reservoir water was made. The work presented here is a laboratory based evaluation of NOM treatment by UV-C photolysis, UV/H 2O 2, Fenton’s reagent (FR) and photo-Fenton’s reagent (PFR). The work investigated ways of reducing the organic load on water treatment works (WTWs) with a view to treating ‘in-reservoir’ or ‘in-pipe’ before the water reaches the WTW. The efficiency of each process in terms of NOM removal was determined by measuring UV absorbance at 254 nm (UV 254) and dissolved organic carbon (DOC). In terms of DOC reduction PFR was the most effective (88% removal after 1 min) however there were interferences when measuring UV 254 which was reduced to a lesser extent (31% after 1 min). In the literature, pH 3 is reported to be the optimal pH for oxidation with FR but here the reduction of UV 254 and DOC was found to be insensitive to pH in the range 3–7. The treatment that was identified as the most effective in terms of NOM reduction and cost effectiveness was PFR.

Application of O3/GAC process for advanced and selective removal of natural organic matter from conventionally treated water

A demonstration plant consisted of ozone/granular activated carbon (GAC) was operated using sand filtered water as an influent to study the feasibility for introduction of an advanced water treatment. In ozonating the sand filtered water, dissolved organic carbon (DOC) slightly increased at an ozone dose of less than 1.0 mg O3/mg C, and the largest DOC reduction was exhibited at 1.0 mg O3/mg C. As ozone dosage increased from 1.0 to 5.0 mg O3/mg C, DOC decreased no more, whereas UV absorbance at 254 nm gradually decreased with increasing ozone dosage. The hydrophobic fraction in natural organic matter (NOM) was considered as a predominant reactant from the result of a rapid decrease in specific ultraviolet absorbance (SUVA). Since the specific reaction sites in the NOM molecule for haloform reaction were attacked by ozonation, the disinfection by-product (DBP) formation potentials could be reduced. The hydrophobic fraction decreased from 36.3% to 28.7% by ozonation and then decreased to 24.2% through carbon adsorption. The hydrophilic fraction changed only by 1.0% during ozonation, while it decreased by 28.3% through carbon adsorption. Therefore, ozonation followed by carbon adsorption is an acceptable process for the reduction of latent risk through selective oxidation and adsorption of different NOM fractions.

Application of improved rapid mixing for enhanced removal of dissolved organic matter and DBPFP (disinfection by-product formation potential) control

Dispersion of metal coagulant should be completed in a fraction of a second before the metal hydroxide precipitate has formed. For this reason, so-called pump diffusion flash mixing (PDFM) has been proposed, and PDFM is one reasonable method to quickly disperse the hydrolyzing metal salts. In this study, we attempt to understand the difference of removal characteristics of natural organic matter (NOM) between PDFM and conventional rapid mixing (CRM) in a water treatment system, and to enhance the removal of NOM through the improved mixing process. Dissolved organic carbon (DOC) and turbidity removal by PDFM was higher than those by CRM, while specific ultraviolet absorbance (SUVA) of treated water by PDFM was higher than that by CRM. NOM was more effectively removed by PDFM compared to CRM due to quick and uniform dispersion of coagulants. Though the hydrophilic fraction found as major faction in bulk NOM from Han River water is enriched in haloacetic acid precursor sites as compared to hydrophobic fraction, the hydrophilic fraction was more effectively removed by PDFM rather than CRM. Therefore, PDFM is effective and innovative process in reduction of DOC and DBPFPs as well as turbidity, and requires lower coagulant dosage compared to CRM.

Changes in dissolved organic carbon of soil amendments with aging: effect on pesticide adsorption behavior.

The effect of aging in the soil of three organic amendments (OAs), one liquid (LF) and two solid ones (SF and AL), has been investigated and related to changes in soil adsorption of metalaxyl and tricyclazole. LF and AL have very high dissolved organic carbon (DOC) contents with low humification index values, whereas SF has a low DOC content but the highest amounts of highly humified material. All OAs increased the adsorption of tricyclazole, whereas adsorption of metalaxyl decreased in soils amended with LF and AL, due to competition with DOC for mineral adsorption sites. With aging, DOC from SF amended soils is not significantly affected and neither is adsorption behavior. On the contrary, the great reduction of DOC from LF and AL with aging has been shown to affect adsorption of metalaxyl and tricyclazole, and this effect is dependent on the pesticide, the nature of the DOC, and the type of soil, in particular its clay mineralogy.

A comparison of laboratory and pilot plant experiments on the combination of flocculation/ultrafiltration for direct potable water treatment of river water

A direct treatment of river waters with ultrafiltration is not yet realised in larger scales due to considerable fouling and scaling effects caused by water contaminants on the membranes surface under those circumstances. Therefore, the deposits on the membrane cannot be eliminated extensively by conventional backwashing. An extensive detachment of the formed layers while backwashing is desired to achieve cost advantages when using the process combination flocculation/ultrafiltration for the direct treatment of surface waters. Hence, pilot and laboratory plant experiments were carried out while dosing different coagulants at different pH-values with different concentrations of the coagulant to investigate their influence on the build-up of the coating layers. The experiments described here were focused on the following questions. Firstly, how do coagulation and flocculation conditions influence the performance of the treatment combination flocculation/ultrafiltration and which coagulant is best? Secondly, does a good operational performance of the combination flocculation/ultrafiltration at laboratory scale coincide with good operational performances at the pilot plant or does the presence of dissolved organic carbon (DOC) in the raw water decrease the performance significantly? Thirdly, does a good operational performance coincide with an extensive reduction of DOC, or humic substances, respectively?

Riverbank filtration—fate of DBP precursors and selected microorganisms

At three drinking water utilities in the midwestern United States, significant reductions were observed in total organic carbon (TOC), dissolved organic carbon (DOC), and disinfection byproduct precursors after riverbank filtration (RBF). TOC and DOC reductions at the closer wells at the three sites ranged from 35 to 67%. Trihalomethane formation potential and haloacetic acid formation potential concentrations were reduced by 50 to 80% at the three sites. Reductions in precursors for haloacetonitriles, haloketones, chloral hydrate, and chloropicrin ranged from 30 to 100% following RBF. Reductions in the concentrations of Clostridium were observed in excess of 3 logs. Log reductions in the rivers and wells ranged from >2.6 to >3.3 for E. coli C bacteriophage and from >1.9 to >2.3 for E. coli F‐amp bacteriophage. Limited occurrence of Giardia and Cryptosporidium in the river and well waters prevented the establishment of firm conclusions for the removal of these organisms.

Cold Water Effects on Enhanced Coagulation of High DOC, Low Turbidity Water

Abstract Prairie farm reservoirs are usually low in turbidity and contain high concentrations of dissolved organic carbon (DOC). Some are treated with aluminum sulfate in late fall when the water drops below 3°C, often with poor turbidity reduction results. Jar tests using aluminum sulfate were conducted to study the effect of water temperature on enhanced coagulation of a typical high DOC prairie water. Jar tests showed that temperature affects turbidity, particle counts and total residual aluminum but does not affect DOC, UV254 absorbance and colour reduction. Turbidity of the treated water increased consistently as the temperature decreased. Particle counts in the 1 to 10 μm range were reduced by two logs at 20°C but only by one log at 1.5°C indicating inferior oocyst removal at low temperatures. Bentonite addition at 1.5°C did not affect the treated water particle counts but because the bentonite increased the raw water particle count, the reduction of the particles could be increased by one log. Coagulant demand for the water tested without pH adjustment is one to two mg Al per mg of DOC at all temperatures tested. The optimum pH for all temperatures was about 6.0 for DOC removal and about 6.5 for turbidity removal based on a dosage increment of 0.5 pH units. UV254 absorbance is well suited to predict optimum aluminum sulfate dosage for DOC removal.

Assessment of the pollutant elimination efficiency by gas chromatography/mass spectrometry, liquid chromatography–mass spectrometry and –tandem mass spectrometry: Comparison of conventional and membrane-assisted biological wastewater treatment processes

The elimination efficiency of advanced conventional biological wastewater treatment was compared to membrane-assisted biological wastewater treatment. The sum parameter analyses dissolved organic carbon (DOC) and chemical oxygen demand (COD) or substance-specific analyses such as gas chromatography combined with mass spectrometry, flow injection analysis (FIA–MS) and liquid chromatography (LC–MS) in combination with mass or tandem mass spectrometry (MS–MS) were applied to assess elimination of hardly eliminable compounds in both types of wastewater treatment plants (WWTP). Reduction of DOC and COD in wastewater treatment processes confirmed a favourable elimination efficiency. Substance-specific methods which were applied in addition permitted a qualitative and semi-quantitative assessment of elimination with a visual pattern recognition approach. In order to identify pollutants either the NIST library of electron impact mass spectra for unpolar compounds or the laboratory-made collision-induced dissociation spectra library for polar pollutants was used. To assess elimination efficiency FIA–MS in the selected ion monitoring mode (SIM) besides high selective substance-specific mass spectrometric techniques such as parent ion scans and neutral loss scans were used for quantification. Results proved that membrane-assisted treatment was more effective than advanced biological treatment. In both types of WWTPs predominantly unpolar pollutants were eliminated, while all effluents were dominated by polar compounds of anthropogenic and biogenic origin. These unpolar and polar compounds which had been identified as hardly eliminable are reported about. Quantitative results obtained by FIA–MS, LC–MS and MS–MS for the elimination of alkyl polyglycol ethers, nonylphenol ethoxylates and linear alkylbenzenesulfonic acids from wastewater are presented.

Advanced Treatment Combination for Groundwater Recharge of Municipal Wastewater by Nanofiltration and Ozonation

This paper presents the results of research undertaken on an advanced treatment combination for polishing municipal wastewater with the purpose of a safe groundwater recharge. The results of a former study of DWQC initiated this research. It is envisaged that tertiary effluent is nanofiltrated to reject dissolved organic carbon (DOC) and adsorbable organic halogens (AOX) to concentrations less than 2–3 mg DOC/L respectively <2 μg AOX/L. The brine will be given back in a recycling process to the sewage treatment plant after passing an oxidation step. To avoid rising scaling potentials and other negative impacts due to increasing salinity, the rejection characteristics of several NF-membranes were investigated. They show a strong dependence between DOC and sulfate removal. Biofouling on the membrane surface (Desal DK5) can be controlled by higher cross-flow velocities (CFV) of about 1 m/s, however, a suitable pre-treatment like slow sand filtration is required. High water conversion factors result in moderately higher biofouling. This shows that water quality is the main factor responsible for fouling and not the concentration of constituents. Ozonation experiments with the concentrate confirmed an enhanced biodegradability of refractory DOC. At a specific ozone consumption 1,7 mg O3/mg DOC0 the DOC reduction by micro-organisms (aerobic biotest) reaches its maximum after 14 days of biodegradation with a total reduction of 60%.

Carbohydrate dynamics and contributions to the carbon budget of an organic-rich coastal sediment

Potential hydrolysis rates of three different polysaccharides, pullulan, laminarin, and xylan, were measured in intact sediment cores from Cape Lookout Bight, North Carolina, in order to constrain the rates at which a fraction of the high-molecular-weight sedimentary carbon pool may be hydrolyzed to lower molecular weights. Potential hydrolysis rates of pullulan were somewhat higher than those of laminarin and xylan. Highest potential rates were measured in surface sediments; rates at depths of 5–7 and 14–16 cm differed relatively little from one another. Total dissolved carbohydrates, dissolved organic carbon (DOC), sulfate, and sulfate reduction rates were also measured and compared with data previously collected at Cape Lookout Bight in order to investigate carbohydrate dynamics and establish the relative contribution of carbohydrates to the sedimentary carbon budget. Total porewater carbohydrates constitute a disproportionate fraction of DOC, ranging from a maximum of 85% in near-surface intervals to 24% at depths of 14–16 cm. A comparison of potential hydrolysis rates, dissolved carbohydrate concentrations, DOC, and sulfate reduction rates, along with results from a wide range of studies previously conducted at this site suggests that hydrolysis of high-molecular-weight polysaccharides can potentially be very rapid relative to carbon remineralization rates. Dissolved porewater carbohydrates form a dynamic pool that is likely turned over on short timescales in Cape Lookout Bight sediments.

Advanced treatment combination for groundwater recharge of municipal wastewater by nanofiltration and ozonation

This paper presents the results of research undertaken on an advanced treatment combination for polishing municipal wastewater with the purpose of a safe groundwater recharge. The results of a former study of DWQC initiated this research. It is envisaged that tertiary effluent is nanofiltrated to reject dissolved organic carbon (DOC) and adsorbable organic halogens (AOX) to concentrations less than 2–3 mg DOC/L respectively <20 μg AOX/L. The brine will be given back in a recycling process to the sewage treatment plant after passing an oxidation step. To avoid rising scaling potentials and other negative impacts due to increasing salinity, the rejection characteristics of several NF-membranes were investigated. They show a strong dependence between DOC and sulfate removal. Biofouling on the membrane surface (Desal DK5) can be controlled by higher cross-flow velocities (CFV) of about 1 m/s, however, a suitable pre-treatment like slow sand filtration is required. High water conversion factors result in moderately higher biofouling. This shows that water quality is the main factor responsible for fouling and not the concentration of constituents. Ozonation experiments with the concentrate confirmed an enhanced biodegradability of refractory DOC. At a specific ozone consumption of 1,7 mg O3/mg DOC0 the DOC reduction by micro-organisms (aerobic biotest) reaches its maximum after 14 days of biodegradation with a total reduction rate of 60%.

Removal of substituted pyridines by combined ozonation/fluidized bed biofilm treatment

3-Methylpyridine (MP) and 5-ethyl-2-methylpyridine (EMP) were quantitatively removed in batch ozonation. Formate, acetate and oxalate where detected as ozonation products representing only about 10% of the total organic carbon after 90% removal of MP. Only 30% of the nitrogen was detected as nitrate. 5 moles of ozone were needed per mol of MP removed but at this time dissolved organic carbon (DOC) was only reduced by 10%. EMP was initially oxidised much faster but the reduction of DOC was only 5% when EMP was removed by 90%. Only 15% of the nitrogen was converted to nitrate. Small amounts of formate, acetate and oxalate were accumulated. 4 moles of ozone were required to remove one mole of EMP. In continuous combined experiments, wastewater was fed to a fluidised bed biofilm reactor with a mixed culture. The liquid was circulated through an ozonation bubble column. Ozone supply was controlled to keep the dissolved ozone concentration at a low level in the oxidation reactor. Complete mineralisation of MP and extensive mineralisation of EMP was observed during the whole experiment. During adaptation of biomass the ozone requirement decreased from 10 mol mol−1 of MP oxidised to 4 mol mol−1.

Removal of substituted pyridines by combined ozonation / fluidized bed biofilm treatment

3-Methylpyridine (MP) and 5-ethyl-2-methylpyridine (EMP) were quantitatively removed in batch ozonation. Formate, acetate and oxalate where detected as ozonation products representing only about 10% of the total organic carbon after 90% removal of MP. Only 30% of the nitrogen was detected as nitrate. 5 moles of ozone were needed per mol of MP removed but at this time dissolved organic carbon (DOC) was only reduced by 10%. EMP was initially oxidised much faster but the reduction of DOC was only 5% when EMP was removed by 90%. Only 15% of the nitrogen was converted to nitrate. Small amounts of formate, acetate and oxalate were accumulated. 4 moles of ozone were required to remove one mole of EMP. In continuous combined experiments, wastewater was fed to a fluidised bed biofilm reactor with a mixed culture. The liquid was circulated through an ozonation bubble column. Ozone supply was controlled to keep the dissolved ozone concentration at a low level in the oxidation reactor. Complete mineralisation of MP and extensive mineralisation of EMP was observed during the whole experiment. During adaptation of biomass the ozone requirement decreased from 10 mol mol-1 of MP oxidised to 4 mol mol-1.

Toxicity estimation of treated coke plant wastewater using the luminescent bacteria assay and the algal growth inhibition test

AbstractAmong several bioassays, the Scenedesmus subspicatus chlorophyll fluorescence test and the Photobacterium phosphoreum bioluminescence assay were selected to examine their applicability for toxicity evaluation of changes in coke plant effluent quality. In addition to the ecotoxicological parameters, a chemical analysis of dissolved organic carbon (DOC), ammonia‐N, and nitrate‐N was performed.It was demonstrated that the toxicity values obtained from the bioassays give a first indication on potential hazard and successful treatment. Decreasing toxicity values went along with decreasing DOC or ammonia‐N values, but the sensitivity toward DOC reduction was higher. Sensitivity toward pure compounds was assessed by comparing the EC50 values of the luminescent bacteria assay with the corresponding EC50 values of the algal bioassay. The data showed a poor correlation between the two bioassays. © by John Wiley &amp; Sons, Inc.

Colloidal and dissolved organic matter in lake water: Carbohydrate and amino acid composition, and ability to support bacterial growth

Bacterial utilization of dissolved organic matter (DOM) was studied in water from a humic and a clearwater oligotrophic lake. Indigenous bacteria were inoculated into either 0.2 μm natural filtered lake water, or lake water enriched fivefold with colloidal DOM >100 kD but below 0.2 μm. Consumption of DOM was followed from changes in concentrations of total dissolved organic carbon (DOC), dissolved combined and free carbohydrates and amino acids (DCCHO and DFCHO, and DCAA and DFAA, respectively) and by uptake of monosaccharide and amino acid radioisotopes. DCCHO and DCAA made up 8% (humic lake) to 33–44% (clear-water lake) of the natural DOC pools, while DFCHO and DFAA contributed at most 1.7% to the DOC pools. Addition of >100 kD DOM increased the DOC concentrations by 50% (clearwater lake) to 92% (humic lake), but it only resulted in a higher bacterial production (by 63%) in the humic lake. During the incubations 13 to 37% of the DOC was assimilated by the bacteria, at estimated growth efficiencies of 4–8%. Despite the measured reduction of DOC, statistically significant changes of specific organic compounds, especially of DCCHO and DCAA, generally did not occur. Probably the presence of high molecular weight DOC interfered with the applied analytical procedures. Addition of radiotracers indicated, however, that DFAA sustained 17–58% and 29–100% of the bacterial carbon and nitrogen requirements, respectively, and that glucose met 1–3% of the bacterial carbon requirements. Thus, our experiments indicate that radiotracers, rather than measurements of concentration changes, should be used in studies of bacterial utilization of DOC in freshwaters with a high content of humic or high molecular weight organic matter.

Retention of Dissolved Organic Carbon and Sulfate in Aggregated Acid Forest Soils

AbstractAdsorption of dissolved organic carbon (DOC) and sulfate was examined in mineral A and B horizons of aggregated acid forest soils from declining (Oberwarmensteinach) and healthy (Wülfersreuth) Norway spruce [Picae abies (L.) Karst.] stands in northeastern Bavaria, Germany. Adsorption studies were conducted in the laboratory on undisturbed, aggregated soil samples under nonequilibrium conditions using a miscible displacement method. Initial mass relationships suggest a net release of DOC in the A horizons of both stands at all DOC concentration levels added. In contrast, the B horizons retained DOC from solutions containing more than 4 to 5 g C m−3 in the Oberwarmensteinach B horizon, and 2 to 3 g m−3 in the Wülfersreuth B horizon, respectively. These concentrations correspond to mean annual DOC concentrations in the B horizon solutions of both sites. Addition of sulfate (1.60 molc SO4 m−3) significantly reduced DOC retention, suggesting competition between SO4 and parts of DOC for adsorption sites. Retention of sulfate from solution occurred concentrations with more than 0.38 to 0.42 molc SO4 m−3 in Oberwarmensteinach, and 0.25 to 0.31 molc SO4 m−3 in Wülfersreuth, respectively. Compared with batch experiments, the miscible displacement method resulted in lower affinities of the soils for DOC. Reduction of DOC and sulfate retention by the use of the flow‐generated technique is due to the consideration of sorption kinetics, which are influenced by soil structure and texture. Although this method underestimates the affinity of a soil for DOC to a certain extent, we suggest that it reflects the situation in the field quite well. Flow‐generated experiments showed that the decline phenomena of spruce in Oberwarmensteinach correspond with a reduced potential for DOC retention in the upper B horizon, as well as with lower sulfate retention throughout the profile.