Trihalomethane Formation Potential Research Articles

Pre-oxidation strategies for biofiltration performance improvement

This study examined the impact of ozone (O3) and hydrogen peroxide+ozone (H2O2+O3) on organic matter and subsequent DOC and DBP precursor uptake across biofilters. Organic matter fractionation, using liquid chromatography – organic carbon detection (LC-OCD), confirmed that both O3 and H2O2+O3 oxidized high molecular weight fractions (biopolymers and humics) creating smaller, more easily biodegraded compounds (low molecular weight acids). O3 decreased trihalomethane (THM) and haloacetic acid (HAA) formation potential (FP) by 23% and 15% respectively; H2O2+O3 resulted in an increase of 52% and 41%.Biological activated carbon (BAC) removed 6% of DOC; removals increased to 15% and 23% when preceded by O3 or H2O2+O3, respectively. BAC without pre-oxidation reduced THM FP by 12%, compared to 38% and 14% removal with O3 and H2O2+O3, respectively. HAA FP decreased by 36% for O3+BAC and 20% for H2O2+O3+BAC; better performance by O3 was likely due to increased HAA precursor formation by the AOP. BAC was found to perform better than anthracite-based biofilters for all parameters. This study highlights the impact of pre-oxidation on organic composition, the benefits of biofiltration when used in combination with pre-oxidants such as ozone, and the importance of pilot-testing to assess alternative treatment processes.

Removal of Trihalomethane Precursors by Nanofiltration in Low-SUVA Drinking Water

Trihalomethanes (THMs) are prevalent disinfection by-products. High THM formation is usually associated with natural organic matter with high molecular weight and aromatic characteristics, which is efficiently removed by nanofiltration (NF). In the Sea of Galilee and the Israeli National Water Carrier (NWC), water shows high THM formation potential, although it mainly contains low molecular weight and hydrophilic organic matter with low aromaticity. In the present study, NF removal abilities were tested on treated NWC water using three different spiral wound membranes (NF90, NF270, and DL). Rejections and fluxes were tested as a function of pressure, water recovery, and membrane type. Feed and permeate dissolved organic carbon (DOC), UVA254, total THM formation (THMF), and total THM formation potential (THMFP), as well as alkalinity, conductivity, hardness, Ca2+, Mg2+, and Cl− were measured to evaluate rejection and THM formation reduction. The results demonstrated that NF can efficiently remove natural organic matter (NOM) and reduce THM formation, even in this challenging type of water. At low water recovery, membranes showed average rejection of about 70–85% for THMFP and THM. Upon elevating recovery, average THM and THMFP rejection decreased to 55–70%, with THM content still well below regulation limits. Of the membranes tested, the higher permeability of NF270 appears to make it economically favorable for the applications tested in this work.

Disinfection By-Products Formation Potential Along the Melendiz River, Turkey; Associated Water Quality Parameters and Non-Linear Prediction Model

Organic matters in raw water have a potential to generate harmful disinfection byproducts such as trihalomethanes (THMs) and haloacetic acid (HAA) during the chlorination process. The aim of this study was to investigate the trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP) in Melendiz River and to determine the effect of several factors including water quality parameters, distance, and seasonal variation. Water samples (n = 93) were collected at Melendiz River during December 2015–November 2016. The range of THMFP and HAAFP was 47.28–3348.73 μg/L and 41.42–4952.68 μg/L, respectively. ANOVA analysis was performed to understand the impact of the seasonal and/or distance changes on DBPs formation. It was found that the seasonal variations (sig. ≤ 0.01) are more effective than distance variations (sig. > 0.80) at Melendiz River. Finally, a non-linear statistical model was developed based on Multiple Stepwise Regression Analysis using highly correlated water quality parameters with TTHM and THAA5 in Pearson Correlation Analysis. According to the results, among all factors, flow, dissolved organic carbon (DOC), UV254, UV272, bromide, temperature, and additional chlorine dose have a remarkable effect on THMFP and HAAFP. Especially, the Pearson correlation (P) values for the DOC and the Chlorine dosages are 0.583, 0.786 and 0.994 and 0.865 for THMFP and HAAFP models, respectively. In addition to this, the high R2 (0.95) values were obtained when compared to other predictive models. The local model development should be utilized because each water source has different organic characterization. For this reason, the development of local models for each water source is important for achieving more consistent results.

Ozone/peroxide advanced oxidation in combination with biofiltration for taste and odour control and organics removal

The objective of this pilot-scale study was to investigate the effectiveness of incorporating ozone (O3) and advanced oxidation (hydrogen peroxide/ozone: H2O2/O3) in combination with biofiltration for taste and odour control, organic carbon removal, and disinfection byproduct (DBP) precursor reduction. Implementation of O3 and H2O2/O3 with and without biofiltration was investigated at pilot-scale in terms of geosmin, 2-methylisoborneol (MIB), and DBP precursor removal efficiency. Two media types (granular activated carbon and anthracite) were compared in conjunction with investigating the impact of pre-oxidation with O3 (2 mg/L) and varying H2O2/O3 mass ratios (0.1, 0.2, 0.35, and 0.5 mg/mg). When O3 preceded biologically active carbon (BAC) or biologically active anthracite, geosmin removals of 80% and 81%, respectively, were observed at 10 °C; this increased to 89% and 90%, respectively, at 16 °C. Optimal MIB removal (67%) was achieved with 0.1 H2O2/O3 (mg/mg) in combination with BAC at 16 °C.In general, geosmin proved to be more amenable to biodegradation than MIB. BAC without pre-oxidation removed 87% geosmin and 85% MIB, at 22 °C. MIB removals decreased to 60% and 46%, respectively at 16 °C and 10 °C. The application of 0.2 H2O2/O3 (mg/mg) prior to BAC provided treatment which effectively removed geosmin and MIB. However, in terms of DBP precursor reduction, there was no beneficial impact of H2O2 addition on trihalomethane or haloacetic acid formation potentials.

Dynamic variations in dissolved organic matter and the precursors of disinfection by-products leached from biochars: Leaching experiments simulating intermittent rain events

Biochar-leached dissolved organic matter may have a substantial impact on the water quality of receiving water surrounded by biochar-amended fields. In this study, we tracked variations in the spectroscopic characteristics and the disinfection by-products formation potentials of dissolved organic matter (DOM) leached during sequential extraction for three different biochars (BCs), which simulates DOM from BC-amended fields during intermittent rain events. The optical properties of DOM were more dependent on the BC types with different origins (sludge, corn, and rice) rather than on the extraction time. A large amount of DOM was released during the initial period of the extraction (1 day), which was equivalent to 52–60% of the total cumulative organic carbon during 17 days of extraction. The relative contribution of the initial extraction to the total cumulative amounts was greater for the formation potential of trihalomethanes (THMs) per BC (71–82%) compared to those of haloacetic acids (HAAs) or dissolved organic carbon (DOC), suggesting that the leaching behaviors of disinfection byproducts (DBP) precursors from BCs may be different from those of DOC (i.e., bulk DOM). Among the three BCs, corn BC-derived DOM exhibited the highest formation potentials of THMs and HAAs per BC for both the initial and the total cumulative extraction. The specific (or DOC-normalized) THMs formation potential was positively correlated with the ratios of terrestrial humic-like to fulvic-like components, implying condensed aromatic structures could operate as a surrogate for THMs formation of BC-derived DOM. This study provided insight into dynamic leaching behaviors of DOM from BCs and the formation potentials for THMs and HAAs in BC-amended fields under intermittent rainfall.

Research on treating algae-polluted reservoir water by the process of pre-oxidation/dissolved air flotation/carbon sand filter

Abstract As the water diversion reservoir showed high organic matter and high algae in summer, the potassium permanganate pre-oxidation/dissolved air flotation/carbon sand double filter process was developed. The test results show that the optimum operation conditions of the combined process were as follows: the dosage of KMnO4 was 0.3 mg/L, the dosage of polymeric aluminum ferric chloride (PAFC) was 3.0 mg/L (Al3+), the reflux ratio was 10%, and the dissolved gas pressure was 0.3 Mpa. Taking Ji'nan Queshan reservoir water algae pollution as the research object, the average removal rate of chlorophyll a, blue-green algae, turbidity, particle number and total organic carbon (TOC) reached 66.64%, 95.44%, 94.45%, 99.34% and 46.68%, respectively; the methylisoborneol (MIB) removal rate was 92.47%, the odor level decreased with process flow from raw water level 4 to effluent level 1.5, geosmin (GSM) dropped below the detection limit, and the total removal rate of trihalomethane formation potential (THMFP) was 33.56%. The effluent of the combined process meets the requirements of the Hygienic Standard for Drinking Water (GB5749-2006) after it is disinfected.

Impact of biofilter operation on microbial community structure and performance

The objectives of this pilot-scale study were to evaluate biological acclimation of virgin granular activated carbon (GAC), quantify the impact of nutrient (phosphorus and nitrogen) enhancement and to compare the performance of parallel biologically active carbon (BAC) filters operated continuously or cyclically (12 h/day), with respect to removal of dissolved organic carbon (DOC) and disinfection by-product (DBP) precursors. Virgin GAC media outperformed biologically active carbon for an initial 4-month period in terms of DOC reduction (30%), as expected based on the superior performance associated with adsorption compared to biodegradation. Once the adsorptive capacity was exhausted and the media was biologically acclimated, the performance of the new GAC was statistically similar in terms of organic carbon and disinfection by-product precursor removal to a filter containing media harvested from a filter operating biologically for 12 years. Phosphorus addition to the filter influent (0.3 mg PO4-P/L; C:N:P = 400:1:30) had a small impact on DOC (3 ± 2%) and THM formation potential (5 ± 3%) reduction when compared to biofiltration without nutrient enhancement. Ammonia nitrogen added to the filter influent (0.8 mg NH4-N/L; C:N:P = 200:40:1) was completely consumed through the biofilter; however, no impact on measured performance parameters was observed. Cyclical operation of full-scale biofilters resulted in a modest, but significant improvement in DOC removal (3 ± 2%) when compared to continuously operated pilot filters. Genotyping of both cyclically and continuously operated biofilters (with varying GAC ages) showed similar community composition; however, differences in the phylogenetic diversity of the samples were evident.

Modelling of THM formation potential and DOM removal based on drinking water catchment characteristics

Catchment properties influence the character and concentration of dissolved organic matter (DOM). Surface and subsurface runoff from discrete catchments were collected and DOM was measured and assessed in terms of its treatability by Enhanced Coagulation and potential for disinfection by-product (trihalomethane, THMFP) formation potential. Models were developed of [1] DOM character [i.e. SUVA and SpCoL] and concentration (measured as dissolved organic carbon), [2] treatability of DOM by coagulation/flocculation processes and [3] specific THMFP based on the catchment features including: (a) surface and sub-surface soil texture (% clay: 5–25%), (b) topography (% slope: 5–15%) and (c) vegetation cover [i.e. high photosynthetic vegetation, low photosynthetic vegetation and bare soil] extracted from RapidEye satellite imagery using spectral mixture analysis. From these models, a catchment management decision support tool was designed for application by catchment managers to support decision-making of land-use and expected water quality related to water resources for drinking water supply. Software and data availabilityData sets used for models developing presented in this paper have been published in Research Data Australia (RDA) under the title of “Impacts of catchment properties on DOM and nutrients in waters from drinking water catchments”.11Link: https://researchdata.ands.org.au/impacts-catchment-properties-water-catchments/932912?source=undefined. These datasets are provided by the University of South Australia (UniSA). All data in these datasets were collected as part of the Australian Research Council project, ARC Linkage-LP110200208. These data sets are available in open access and published in June 2017. A catchment management decision support model (CMDSM) tool was developed. Macros created using Visual Basic for Applications in Excel 2010. Excel 2010 or higher is required to open the CMDSM tool. The tool is provided by the University of South Australia (UniSA) and is not currently available on-line so please contact the corresponding author for access or further information.

APPLICATION OF PRE-OZONATION FOR REMOVAL OF DISINFECTION BY- PRODUCTS PRE-CURSOR FROM SAIGON RIVER WATER

This study aimed to apply pre-ozonation for removal of disinfection by-products precursors to reduce the formation of trihalomethanes (THMs) in Saigon river water. The pre-ozonation process was conducted in a lab-scale ozone contactor. The raw water sample was collected from Saigon River at the Hoa Phu pump station in Cu Chi District, Ho Chi Minh City. The suitable condition for pre-ozonation was found. At ozone dose of 1.5 mgO3/mgDOC, pH of 8.5, and contact time of 15 minutes, the removal efficiency of turbidity, color, iron, manganese, dissolved organic carbon (DOC), trihalomethanes formation potential (THMFP) were 36 %, 25 %, 56 %, 81 %, 35 %, and 46 %, respectively. These results indicated that the pre-ozonation could reduce DOC concentration and thus resulted in significant mitigation of THMs formation. In comparison with pre-chlorination, THMFP of raw water pretreated by pre-ozonation was lower. Moreover, this study showed that the pre-ozonation was more effective than pre-chlorination in terms of turbidity, color, manganese, and DOC removals.

Fate of bromine-containing disinfection by-products precursors during ozone and ultraviolet-based advanced oxidation processes

This research evaluates the effect of ultraviolet photolysis, ozonation and ozonation/ultraviolet advanced oxidation processes on different disinfection by-product precursors, during the treatment of water with low organic matter and moderate bromide contents. After different combinations of ultraviolent fluence and ozone, the formation potentials of trihalomethanes and haloacetic acids were investigated. Bromine incorporation factors were used to give specific insight into the behaviour of brominated disinfection by-products, and inorganic bromate formation was also determined. The ozone/ultraviolet process was found to be more effective in reducing the total natural organic matter content than ozonation or ultraviolet photolysis alone. Ultraviolet photolysis was more successful removing the precursors of brominated trihalomethanes than chlorinated trihalomethanes, but slightly increased the precursors of both brominated and chlorinated haloacetic acids. During ozonation, reductions in the haloacetic acid formation potential were significantly better than those of the trihalomethanes formation potential (up to 54 and 27%, respectively). In the combined ozonation/ultraviolet process, increasing the ultraviolet fluence had a varying effect on trihalomethane and haloacetic acid precursor behaviour, depending on the ozone dose applied. Bromine incorporation after ozonation alone increased to up to 38% of the total bromide, largely as a result of bromate formation. The combined process curtailed all bromate formation, but increased the bromine incorporation up to 48% at higher ozone doses, with disinfection by-product formation shifting towards the more toxic brominated species.

Characterization and removal of natural organic matter from slow sand filter effluent followed by alum coagulation

Characterization and removal of natural organic matter, which is contained in the effluent of slowsand filters, was observed by alum coagulation under various dosages. In addition to non-purgedable dissolved organic carbon (NPDOC), trihalomethanes formation potential (THMFP) and haloacetic acid formation potential (HAAFP) measurement, high-performance size-exclusion chromatography (HPSEC) with ultraviolet/visible and dissolved organic carbon (DOC) detectors was used to characterize the various organic fractions contained in the water before and after coagulation. The results show that alum coagulation could effectively remove hydrophobic aromatic, which forms mainly humic substances. The reduction in THMFP was found to be higher than that of NPDOC and HAAFP under specific alum dosage, and the former was also found to be proportional to the corresponding reduction in the area of hydrophobic aromatic fraction, mostly humic subtances, as obtained from HPSEC chromatogram with peak-fitting.

Effect of Permanganate Preoxidation to Natural Organic Matter and Disinfection by-Products Formation Potential Removal

Laboratory scale experiments was conducted to examine effect of permanganate (KMnO4) peroxidation in characterizing and to remove natural organic matter (NOM) in source water. The experimental results shows that increasing permanganate dosage could decreased aromatic matter, as indicated by decreasing UV254 and SUVA value about 23% and 28%, respectively. It seems that permanganate preoxidation caused the breakdown of high molecular weight (MW) organics into low MW ones, as represented by increasing NPDOC about 10%. Further, disinfection by-products formation potential (DBPFP) in terms of trihalomethanes formation potential (THMFP) and haloacetic acid formation potential (HAAP) decreased about 15% and 23%, respectively. HAAFP removal is higher than THMFP removal and that DPBFP removal is consistent with UV254 and NPDOC removal.

THMs Precursor Removal Efficiency from Different Wastewater Treatment Technologies Effluents

Treated wastewater is one of the critical practices of sustainable water management. In Palestinian authority region different wastewater technologies are used to produce variety of effluents that are potentially suitable for different purposes. In this study, these different treated wastewater effluents were characterized chemically, biologically, and physically. Results showed that some of these effluents neither comply with Palestinian nor with other global effluent discharge guidelines. Chemical reactivity of five different treated wastewater effluents with chlorine was measured by determining their chlorine demand and total trihalomethane formation potential (TTHMFP). Results showed that different wastewater effluents chemical reactivity with chlorine and TTHMFP is not only dependent on wastewater treatment technology but also is affected by original water source from which was the water emerged. In all cases, measured THMs superseded acceptable drinking water limits. This would indicate responsibility of high percentage of cancer, hepatic and renal diseases among the local people.

Impact of TiO2/UVA photocatalysis on THM formation potential

In drinking water treatment plants, reduction of trihalomethane formation potential (THMFP) can be reached through precursor removal prior chlorine disinfection. In this work, the impact of TiO2/UVA photocatalytic process on THMFP has been studied using different phenolics (phenol, resorcinol, catechol, hydroquinone and gallic acid) and citric acid as NOM surrogates. A solution of each surrogate was photocatalytically treated at pH 7 applying different UVA doses and then chlorinated. Resorcinol oxidation by TiO2/UVA and THMFP reduction go hand in hand, indicating that the intermediates hardly form THMs when chlorinated. For the rest of surrogates, intermediates with medium-high specific THMFP (maximum values 40–120 μg CHCl3 (mg DOC)−1 for phenols; and ∼1000 μg CHCl3 (mg DOC)−1 for citric acid) are initially formed and disappear at higher UVA doses. TiO2/UVA treatment of water matrices with high and low specific UV absorption at 254 nm (SUVA254) (Sigma-Aldrich humic acid, pH 7; and water from Villar del Rey reservoir; Badajoz-Spain), was also investigated. For surface water UVA doses higher than 5 kWh m−3 were needed to achieve a THMFP below 100 μg THM L−1. During water treatment, an initial negative impact of AOPs in general and TiO2/UVA in particular on THMFP is expected.

Catalytic ozonation by palladium–manganese for the decomposition of natural organic matter

Abstract In this study, magnetic nanoparticles of Fe3O4/SiO2/Pd-Mn were synthesized by wet deposition method for heterogeneous catalytic ozonation to remove the organic compounds in water. The as-synthesized Fe3O4/SiO2/Pd-Mn was characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) to clarify its chemical and physical properties. SEM images indicated that the particle size of Fe3O4/SiO2/Pd-Mn was about 50–100 nm. EDS results confirmed with the XRD findings, illustrating that Pd and Mn were successfully coated on the catalyst with the at% of 1.66 and 2.40%, respectively. The degradation efficiency of organics in water was examined by A254 and dissolved organic compounds (DOC). Under heterogeneous catalytic ozonation treatment, the decomposition efficiency of A254 and DOC of raw water, from Te-Chi reservoir, achieved 70 and 60%, respectively. The decomposition efficiency of A254 and DOC increased to 80 and 90% when the pH was adjusted to 11. The calculated DOC degradation rate constant (kd) for was 6.5 × 10−2 min−1 at pH 11 via heterogeneous catalytic ozonation method. Hydroxyl radicals were dominated for the removal of organic compounds in our heterogeneous catalytic ozonation system as an evidence of 7-hydroxycoumarin generation in radical scavenger experiments. In addition, the removal efficiency of THMFPs (Trihalomethane Formation Potentials) was 74 and 38% for Fe3O4/SiO2/Pd-Mn heterogeneous ozonation and sole ozonation, repectively, illustrating the enhanced oxidation ability. The endpoint of ozonation process can be controlled by the modeling results of Nernst simulating as ORPA254 = 27240 − 14755.3 ln[A254] − 2486.91 pH + 2.64 ln[THMFPs].

Optical properties of algogenic organic matter within the growth period of Chlorella sp. and predicting their disinfection by-product formation

Algogenic organic matter (AOM) in eutrophic waters is a well-known precursor to disinfection by-product (DBP) formation in drinking water. This purpose of this study is (i) to characterize the optical properties of AOM origins, including intra- (IOM) and extra-cellular organic matter (EOM), derived from Chlorella sp. growth as precursors to two major carbonaceous DBPs (C-DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs) and (ii) to correlate these optical properties with THM and HAA formation potential (FP) in order to predict DBP formation. The results show that both EOM and IOM had low UV254 and UV280 absorbance during their entire growth phase. While IOM chiefly comprised of aromatic proteins and soluble microbial products-like substances (80% of average fluorescent intensity–AFI), EOM spectra were rich in humic- and fulvic-like substances (60% AFI). However, its chemical nature likely differed from terrestrial humics. In DBPFP tests, IOM was a higher-yielding precursor of THMs and HAAs compared to EOM, regardless its growth status. Consequently, C-DBPFP of IOM was always higher than EOM during four growth phases. Results from DBP tests also showed insignificant variation of EOM-derived THMFP and HAAFP during the algal growth phase, while the algal growth status strongly influenced the yields of IOM-derived THMFP and HAAFP. From correlation analysis, our results showed no correlation between UV absorbance with THMFP and HAAFP. Conversely, the regional AFI showed a good correlation with HAAFP and C-DBPFP. Predicting models based on AFI for the formation of HAAs and C-DBPs consequently yielded great predictability for laboratory AOM-containing water samples, with a coefficient of determination R2=0.879, p<0.01 and R2=0.846, p<0.01. This study indicates a promising application of fluorescent spectra for predicting DBPs derived from algae-rich water sources.

The disinfection and natural organic matter removal performance of electro-synthesized ferrate (VI)

This study investigated the efficiency of electro-synthesized ferrate (VI) on the degradation of humic acid (HA) and removal of E. coli for different samples. For providing complete inactivation of E. coli, >1.5mgL−1 ferrate (VI) concentration should be applied for only E. coli containing samples. For only HA containing sample, 60% DOC removal was achieved with 25mgL−1 ferrate (VI). Ferrate (VI) was found to be more efficient at initial pH of 7 (pHi). For HA/E.coli containing samples, ferrate (VI) concentration should be increased to 260mgL−1 for complete inactivation of E. coli. Specific UV absorbance (SUVA) values of raw samples showed that the samples mostly consist of high molecular weight and high hydrophobicity. After the treatment by ferrate (VI); while almost all hydrophobic part was removed, a small portion of hydrophilic part was also removed for only HA containing sample. However, for treated HA/E. coli containing sample, the aromatic removal took place but lower and higher molecular weights of NOM was still in the media in the presence of bacteria. The electro-synthesized ferrate (VI) lowered the trihalomethane formation potential. The residual total iron concentration was 1.14mgL−1 at 1min of process time and then remained stable. This means that ferrate (VI) was consumed as soon as it was applied and reduced to Fe+3/Fe+2.

Comparative assessment of ceramic media for drinking water biofiltration

Media type is a critical design consideration when implementing biofiltration for drinking water treatment. Granular activated carbon (GAC) has been shown to provide superior performance when compared to a wide range of media types, largely due to its higher surface area. Engineered ceramic media is an attractive alternative to GAC as it has a similar surface area but at a lower cost.This pilot-scale biofiltration study compared the performance of GAC, anthracite and two different effective sizes of ceramic (CER) media (1.0 mm and 1.2 mm), in terms of dissolved organic carbon (DOC), head loss, turbidity, and disinfection by-product formation potential (DBPFP). Biological acclimation was monitored using adenosine tri-phosphate (ATP) measurements; biomass was further examined using laccase and esterase enzyme activity assays.When compared to other media types examined, biological GAC had higher (p > 0.05) removals of DOC (9.8 ± 3.8%), trihalomethane formation potential (THMFP, 26.3 ± 10.2%), and haloacetic acid formation potential (HAAFP, 27.2 ± 14.0%). CER media required 6–7 months to biologically acclimate, while filters containing GAC and anthracite were biologically active (>100 ng of ATP/g media) following 30–45 days of operation. Once acclimated, ATP values of 243 and 208 ng/g attained for CER 1.0 and 1.2, respectively, were statistically comparable to GAC (244 ng/g) and higher than anthracite (110 ng/g), however this did not translate into greater organics removal. Esterase and laccase enzyme kinetics were highest for GAC, while CER was shown to have greater biodegradation potential than anthracite. The four media types attained similar turbidity reduction (p > 0.05), however ceramic media filters were observed to have run times which were 1.5–2.3 times longer when compared to anthracite, which could represent potential cost savings in terms of energy for pumping and backwash requirements. Overall, ceramic media was shown to be a potential alternative to anthracite when considering biofiltration, especially during cold water conditions (T < 10 °C).

Biofiltration optimization: phosphorus supplementation effects on disinfection byproduct formation potential

Abstract This study investigates the effects of phosphorus supplementation on the formation potential of total trihalomethanes (TTHMfp) and five species of haloacetic acids (HAA5fp) during exposure to clearwell disinfection contact times. In addition, the study investigates the effects of phosphorus supplementation on the dissolved oxygen, organic carbon and nitrogen removal along with biofilm coverage of the filter media and biomass viability of the attached biofilm. The uptake of total phosphorus in the P enhanced filter did not correspond to the consumption of readily assimilated nitrogen or the consumption of soluble carbon. As such, the dissolved organic carbon reduction in the biologically active filters was shown to not be phosphorus nutrient limited. The clearwell TTHMfp was shown to be reduced in all filters across all measured biological filtration times in the control and P enhanced filters. The HAA5fp increased with phosphorus-supplemented operation at specific filtration cycle times as compared to non-phosphorus-supplemented operation, indicating the potential for production of HAA5 with phosphorus supplementation. Enhanced biofilm coverage of the anthracite and sand media was observed during phosphorus supplementation. In addition, increased viability of the cells embedded in the biofilm was observed in the sand media at depth during phosphorus-supplemented operation.

Effect of ozonation on the characteristics of effluent organic matter fractions and subsequent associations with disinfection by-products formation

Ozonation could be used in advanced wastewater treatment plants to reduce the precursors of disinfection by-products (DBPs), or for disinfection and oxidation of trace organic compounds. Detailed analysis of effluent organic matter (EfOM) is intrinsic to the understanding of impact of ozonation on the characterization variation of EfOM, which is closely related with DBPs formation during subsequent chlorination. In this study, the raw as well as oxidized EfOM with ozone were fractionated into hydrophobic acids, neutrals and bases, and hydrophilic acids, neutrals and bases. Results indicated that ozonation increased the proportion of hydrophilic fractions in EfOM, especially of hydrophilic acids, which resulted in increased specific haloacetic acids formation potential (HAAFP) in the subsequent chlorination. Although ozonation decreased the total organic carbon and SUVA254 of EfOM and most isolated fractions, further ozonation increased the SUVA of hydrophilic acids after the initial decrease. This was in accordance with the chemical structures analysis with FTIR, which showed the relative abundance of unsaturated structures such as CO bonds in hydrophilic fractions increased with further ozonation. Furthermore, specific trihalomethanes formation potential (THMFP) of each fraction decreased after initial pre-ozonation but increased with different extent with further ozonation. While for HAAs, pre-ozonation of hydrophilic acids significantly increased the dichloroacetic acid (DCAA) formation potential. In brief, EfOM containing a relatively high content of aromatic structures i.e. SUVA254 and aliphatic structures yielded a remarkably high specific DBPFP. Further mineralization of organic fractions and specific increased formation of aliphatic CH structures by further ozonation caused the increased DBPFPs especially DCAAFP during subsequent chlorination.