Dissolved Organic Carbon Removal Research Articles

A multi-component model for granular activated carbon filters combining biofilm and adsorption kinetics

Along with the rise of biological active granular activated carbon (bGAC) filtration as advanced treatment technology for wastewater treatment plant (WWTP) effluents, the mathematical representation of such systems is gaining increasing importance. This work introduces a model that describes the performance of bGAC-filters for Dissolved Organic Carbon (DOC) removal from a WWTP effluent. The DOC removal within bGAC-filters is accomplished by two mechanisms: adsorptive removal and biological transformation. An appropriate representation of the adsorptive removal requires the DOC to be divided into fictive fractions according to its adsorbability. Likewise, a further DOC classification according to its biodegradability is necessary. Modeling a bGAC-filter then becomes a multi-component adsorption problem, with the simultaneous occurrence of DOC degradation within a biofilm. For dealing with this modeling task, this work integrated the Ideal Adsorbed Solution (IAS) theory into a traditional biofilm model compatible with the Activated Sludge Model (ASM) Framework. For the description of the adsorption dynamics, a Freundlich isotherm for the equilibrium and a pseudo first order model for the kinetics were selected. The biofilm consisted of heterotrophic bacteria able to oxidize DOC using oxygen as electron acceptor. The correctness of the model was evaluated using experimental data from a pilot plant. The predicted DOC breakthrough curve satisfactorily fitted the experimental measurements for empty bed contact times (EBCT) of 6, 12, 24 and 33 min. Moreover, the model predicted the relationship between EBCT, DOC removal and bGAC-filter lifespan. The developed model is the first that combines multi-component adsorption and biofilm kinetics in a wastewater treatment context.

Organics removal from shale gas wastewater by pre-oxidation combined with biologically active filtration

Biological treatment technology is increasingly explored in shale gas wastewater (SGW) treatment owing to its cost effectiveness and requires efforts to improve its efficacy. In this work, ozone and ferrate(VI) oxidation pre-treatment were evaluated to enhance the performance of the subsequent biologically active filtration (BAF) in the removal of organic contaminants. The oxidation improved the SGW biodegradability and organic composition under relative high salinity (~20 g/L). Due to the degradation activity of microorganisms, the organics removal efficiency in the BAF system was observed to gradually improve and then reaching stability in long-term continuous-mode operation. The removal rate of dissolved organic carbon (DOC) of the ozone-BAF (O3-BAF) and the ferrate(VI)-BAF (Fe(VI)-BAF) systems was 83.2% and 82.8% , respectively, higher than that of BAF alone (80.9%). This increase was attributed to higher activity and content of microorganisms in O3-BAF and Fe(VI)-BAF systems. Two uncultured bacterial species with high abundance of 7.2-21.0% and 2.24-22.31% in genus Rehaibacterium and genus Methyloversatilis were significantly correlated with DOC removal and fluorescent organics removal, respectively. More research is needed to understand whether the species were new and their specific function. This study provides valuable suggestions for extracting safe water from SGW with an efficient treatment train.

Biological ion exchange capable of sulphate-based secondary ion exchange during long-term DOC removal

Biological ion exchange (BIEX) offers removal of dissolved organic carbon (DOC) with greatly reduced regeneration frequency. In the present work, a strong base anionic exchange resin was operated without regeneration and using inlet water with either Low (12 mg L−1) or High (60 mg L−1) sulphate and DOC of 2.75 or 5.0 mg L−1. Filters operated continuously for 226 days (16,500 bed volumes) and achieved DOC removal varying from 32% to 50%. Initially, sulphate and DOC were retained by the resin with chloride being released. During this period, DOC removal occurred due to traditional mechanisms, referred to as primary ion exchange. Following this initial period, DOC removal continued even though the conventionally defined resin capacity was exhausted (based on chloride loading). During the later period, no chloride release was observed, but instead sulphate was released. Although suggested by others, the present study is the first to confirm the direct exchange in charge equivalence of anions removed (DOC and nitrate) to released (sulphate) during the secondary ion exchange mechanism. Further, increasing inlet sulphate from 12 to 60 mg L−1 resulted in a 19% decrease in DOC removal. Finally, percent DOC removal was affected only by an increase of inlet DOC but not changes to the counter ion or after DOC loading on the resin increased to 1/3 of total capacity. This work promotes BIEX as a viable alternative to biological activated carbon and a leading solution for low-maintenance DOC removal.

Fenton pre-oxidation of natural organic matter in drinking water treatment through the application of iron nails

ABSTRACT This study investigated for the first time the efficiency of an advanced oxidation process (AOP) zero valent iron/hydrogen peroxide (ZVI/H2O2) employing iron nails for the removal of Natural Organic Matter (NOM) from natural water of Regent’s Park lake, London, UK. The low cost of nails and their easy separation from the water after the treatment make this AOP attractive for water utilities in low- and middle-income countries. The process was investigated as a pre-oxidation step for drinking water treatment. Results showed that UV254 removal in the natural water was lower than that of simulated water containing commercial humic acid (HA), indicating a matrix effect. Statistical analysis confirmed the maximum removal of dissolved organic carbon (DOC) in natural water depends on the initial pH (best at 4.5) and H2O2 dosage (best at 100% excess of stoichiometric dosage). DOC and UV254 removals under this operational condition were 51% and 89%, respectively. Molecular weight (MW) and specific UV absorbance (SUVA254) were significantly reduced to 74% and 78%, respectively. Formation of Chloroform THM in natural water sample after the ZVI/H2O2 process (initial pH 4.5) was below the limit for drinking water, and 48% less than the THM formation in the same water not subjected to pre-oxidation. Characterization of oxidation products on the iron-nail-ZVI surface after the ZVI/H2O2 treatment by SEM, XRD, and XPS identified the formation of magnetite and lepidocrocite. Results suggest that the investigated ZVI/H2O2 process is a promising technology for removing NOM and reducing THM formation during drinking water treatment.

Removal of antibiotic resistance genes from secondary effluent by processes combining nano-iron, ultrasound-activated persulfate, and ultrafiltration.

Antibiotic resistance genes (ARGs), as a new type of environmental pollutant that threaten human health, have been detected in the effluent of sewage treatment systems. In this study, the removal from water of ARGs, 16S rRNA, class 1 integron (intI1), and dissolved organic carbon (DOC) were investigated using processes combining nano-iron (nFe), ultrasound (US), activated persulfate (PS) and ultrafiltration (UF). The oxidation mechanism was also studied. The results showed that both nFe and US activation could improve the oxidative effect of PS, and the effect of nFe was better than that of US. Compared with PS-UF, nFe/PS-UF and US/PS-UF significantly enhanced the removal of various ARGs and DOC. nFe/PS-UF was the most effective treatment, reducing cell-associated and cell-free ARGs by 1.74-3.14-log and 1.00-2.61-log, respectively, while removing 30% of DOC. Pre-oxidation methods using PS, nFe/PS, and US/PS significantly enhanced the efficacy of UF for removing DOC with molecular weights above 50 kDa and below 10 kDa, but the removal of DOC between 10 and 50 kDa decreased. The free radicals SO4·- and ·OH were shown to participate in the process of ARGs oxidation.

Green aerogel adsorbent for removal of organic compounds in shale gas wastewater: High-performance tuning and adsorption mechanism

The complex organic compounds in shale gas flowback and produced water (SGFPW) pose threats to environmental safety and aggravate membrane fouling during membrane combined processes for SGFPW reuse. The high adsorption efficiency and capacity of aerogel revealed the tremendous potential for removing organics from SGFPW. In this study, we utilized a facile tuning method for porous biochar aerogel (PBA) to improve the adsorption performance of organic compounds in SGFPW as well as identified the adsorption mechanism by analyzing the organics characterization and PBAs’ physicochemical properties. The PBAs were tailored by altering urea and KOH concentration, and the maximum adsorption removal (56.4%) and capacity (205.86 mg/g) of dissolved organic carbon (DOC) was obtained by the optimally tuned PBA-A11.5U12.0 (PBA tuned by 11.5 wt% KOH and 12.0 wt% urea) with a fast adsorption rate (0.012 g/(mg·min)), exceeding the DOC removal from shale gas wastewater by other carbon adsorbents reported. The characterization of organic compounds in SGFPW was identified by measuring fluorescence compounds and organic fractionation, which showed that the humic substances, aromatic proteins, and hydrophobic organics were much tended to be adsorbed by PBAs. Combined with principal component analysis, the organics adsorption mechanism was further identified, indicating the considerable contribution of electron-donor–acceptor interaction, hydrophobic effect, and hydrogen-bond formation. Such a high-efficiency tuned PBA showed decent adsorption performance for various SGFPW as well as good reusability. And it was fabricated from biopolymer with low cost, thus possessing promising prospects in SGFPW treatment.

Export of photolabile and photoprimable dissolved organic carbon from the Connecticut River

Dissolved organic carbon (DOC) impacts water quality, the carbon cycle, and the ecology of aquatic systems. Understanding what controls DOC is therefore critical for improving large-scale models and best management practices for aquatic ecosystems. The two main processes of DOC transformation and removal, photochemical and microbial DOC degradation, work in tandem to modify and remineralize DOC within natural waters. Here, we examined both the photo- and microbial remineralization of DOC (photolability and biolability), and the indirect phototransformation of DOC into biolabile DOC (photoprimed biolability) for samples that capture the spatiotemporal and hydrological gradients of the Connecticut River watershed. The majority of DOC exported from this temperate watershed was photolabile and the concentration of photolabile DOC correlated with UV absorbance at 254 nm (r2 = 0.86). Phototransformation of DOC also increased biolability, and the total photolabile DOC (sum of photolabile and photoprimed biolabile DOC) showed a stronger correlation with UV absorbance at 254 nm (r2 = 0.92). We estimate that as much as 49% (SD = 3.3%) and 10% (SD = 1.1%) of annual DOC export from the Connecticut River is directly photolabile and photoprimable, respectively. Thus, 2.82 Gg C year−1 (SD = 0.67 Gg C year−1) or 1.13 Mg C km−2 year−1 (SD = 0.27 km−2 year−1) of total photolabile DOC escapes photochemical degradation within the river network to be exported from the Connecticut River each year.

DOM Biological Lability in an Estuarine System in Two Contrasting Periods

Estuarine processes play a key role in determining the amount and quality of land-derived dissolved organic matter (DOM) reaching the oceans. Microbial-mediated reactions can affect the concentration, quality, and bioavailability of DOM within an estuary. In this study, we investigated biological DOM removal in a small estuary and its variability in two contrasting seasons (spring and autumn) characterized by natural differences in the concentration and quality of the riverine DOM. Two incubation experiments were carried out using natural DOM and heterotrophic prokaryotes community collected at the estuary in March and September. Dissolved organic carbon (DOC) concentration, DOM fluorescence, and the heterotrophic prokaryotes abundance (HPA) showed marked differences between the two seasons. These parameters were followed through time for up to two months. Despite the marked differences in the initial conditions, the DOC removal rates were surprisingly similar in the two periods (16 µM DOC month−1 in March and 18 µM DOC month−1 in September), with the biggest removal in the first 48 h. The trend of fluorescent DOM (FDOM) during the incubation showed marked differences between the two periods. In March, the net removal of all the FDOM components was observed consistently with the decrease in DOC; whereas, in September, the net production of humic-like substances was observed.

Degradation of Bisphenol A in an Aqueous Solution by a Photo-Fenton-Like Process Using a UV KrCl Excilamp.

Bisphenol A (BPA), a precursor to important plastics, is regarded as a common aquatic micropollutant with endocrine-disrupting activity. In the present study, we explored the capability of a UV KrCl excilamp (222 nm) to degrade BPA by a photo-Fenton-like process using persulfate under flow-through conditions. The first-order rate constants of degradation were obtained and the mineralization of dissolved organic carbon (DOC) was estimated. The results showed complete BPA degradation and high DOC mineralization (70–97%). A comparative analysis of degradation rates and DOC removal in the examined systems (UV, Fe2+/S2O82−, UV/S2O82− and UV/Fe2+/S2O82−) revealed a significant synergistic effect in the photo-Fenton-like system (UV/Fe2+/S2O82−) without the accumulation of toxic intermediates. This indicated that the BPA was oxidized via the conjugated radical chain mechanism, which was based on the photo-induced and catalytic processes involving HO• and SO4−• radicals. The primary intermediates of BPA degradation in the UV/Fe2+/S2O82− system were identified by HPLC/MS and the oxidation pathway was proposed. The high performance of the photo-Fenton-like process employing a quasi-monochromatic UV radiation of a KrCl excilamp offers promising potential for an efficient removal of such micropollutants from aqueous media.

Controlling harmful algal blooms (HABs) by coagulation-flocculation-sedimentation using liquid ferrate and clay

Harmful algal blooms (HABs) occur worldwide and threaten the quality of marine life, public health, and membrane facilities in Seawater Reverse Osmosis (SWRO) desalination plants. The effects of HABs on seawater desalination plants include extensive membrane fouling, increased coagulant consumption and plant shutdown. To determine how to mitigate such effects, this study assessed if low doses (0.01 mg/L, 0.10 mg/L, and 1.00 mg/L) of liquid ferrate (58% yield) and kaolin or montmorillonite clays alone could remove algal organic matter in coagulation-flocculation-sedimentation (CFS) pretreatment desalination systems. Results showed that 0.01 mg/L of liquid ferrate coagulant removed 42% of dissolved organic carbon (DOC), 52% of biopolymers (BP), 71% of algal cells, and 99.5% of adenosine triphosphate (ATP). At a dose of 0.01 mg/L, clays exhibited high removal of turbidity (up to 88%), BP (up to 80%) and algal cells (up to 67%). The combination of liquid ferrate (58% yield) as a coagulant with kaolin or montmorillonite clays as coagulant aids in CFS pretreatment led to 72% removal of DOC, 86% of BP, and 84% of algal cells with a fixed dose of 0.01 mg/L for each. Findings from this study can help SWRO plants improve the performance of pretreatment systems during algal bloom events by reducing the consumption of coagulants while also maintaining high removal efficiencies.

Domestic wastewater treatment in a coupled sequential batch reactor-electrochemical reactor process.

The effectiveness of a sequenced biological-physicochemical reactor system for treating sewage was studied. The biological degradation was conducted in a Sequential Batch Reactor, which had innovative features for simplifying the operation and maintenance of the reactor. The reactor was operated at 4, 6, 8, and 12hr cycle. Up to 82% removal of Chemical Oxygen Demand (COD), 50% removal of Dissolved Organic Carbon (DOC), 45% removal of Total Nitrogen (TN), and 45% removal of Total Phosphorus (TP) were achieved. The treated effluent was further polished in a continuous-flow bipolar-mode electrochemical reactor to remove additional recalcitrant organic matter from the wastewater. The process parameters were optimized using Response Surface Methodology. At the optimum condition (pH=8.7; Current=1.0; reaction time=9.0), up to 90% removal of COD, 67% removal of DOC, 61% removal of TN, and 99.9% removal of TP were achieved in the coupled system. Micropollutants belonging to Pharmaceutically Active Compounds, pesticides, etc., were significantly removed. The coupled system completely removed Salmonella, Pseudomonas, and Staphylococcus. However, coliforms were detected at the outlet samples. A UV or ozone disinfection treatment is recommended for the safe reuse of the treated water for nonpotable purposes. PRACTIONER POINTS: Sequential sequential batch reactor-electrochemical reactor process (SBR-ECR) technology is effective for micropollutant removal from sewage. The coupled SBR-ECR system requires less footprint compared to conventional biological systems for wastewater treatment. Carbon material balance study revealed that more than 60% of carbon escapes from wastewater in the form of CO2.

Potential of biologically activated carbon to improve chlorine stability from biodegradation in surface waters

We report that biological activated carbon (BAC) has the significant potential to improve chlorine stability in the drinking water and dissolved organic carbon (DOC) is not a good indicator of chlorine stability. The BAC followed by enhanced coagulation (EC) could be beneficial for improving chlorine stability. BAC granules obtained from an aged (>26,000-bed volume over a year) BAC column was incubated in the same surface water. The prolonged (58 days) incubation achieved a DOC removal (up to 47%) and improvement of chlorine stability (up to 93% of chlorine reactive agents) with time. Surprisingly, a smaller initial biological removal in DOC (12% or 0.61 mg/L) by BAC substantially improved chlorine stability (64% of chlorine reactive agents), but a further improvement per mg-DOC removal is small. BAC process removes non-coagulable compounds that are chlorine reactive, but at the same time increases the coagulable compounds that are chlorine reactive, implying coagulation after BAC (BAC/EC) is beneficial in stabilising the chlorine and DOC removal. Over the incubation period, a shift in the microbial community is less significant except for the abundance of Nitrospira increasing with the removal in biodegradable organic carbon. BAC treatment followed by coagulation is a good strategy, but the evaluation should be based on chlorine stability and disinfection by-products (DBPs) formation rather than the DOC.

Removal efficiency of dissolved organic matter from secondary effluent by coagulation-flocculation processes

Wastewater reuse has been widely discussed as an essential strategy to minimize the consumption of drinking water for less noble purposes. During biological wastewater treatment, organic matter is converted into a complex matrix containing a variety of soluble organic compounds. The objective of the present study was to evaluate the removal efficiency of the residual organic load in the final effluent from wastewater treatment plant with a conventional activated sludge process by different coagulants and parameters of coagulation-flocculation process, using dissolved organic carbon (DOC) concentration, molecular weight (MW) size distribution by size exclusion chromatography (SEC) coupled to mass spectrometry (MS), and zeta potential (ZP) analyses. The results showed a DOC removal efficiency up to 45% with iron chloride, and of 38% for aluminum sulfate and 31% for PAC coagulants. ZP was also measured during the procedures and authors conclude that the ZP also does not have a determining role in these removals. SEC and MS assessment was able to detect changes on secondary effluent molecular weight distribution profile after effluent coagulation-flocculation, this technique might be a promising tool to understand the composition of effluent organic matter and be helpful to estimate and optimize the performance of wastewater effluents treatment processes.

Enhanced nanofiltration rejection of inorganic and organic compounds from a wastewater-reclamation plant’s micro-filtered water using adsorption pre-treatment

Adsorption pre-treatment to enhance the nanofiltration (NF) removal of inorganic ions, dissolved organic carbon (DOC) and organic micropollutants (OMP) from microfiltered (MF) wastewater was investigated using NF 90 membrane (contact angle 79% and molecular weight cut off value of 90–200 Da). The NF showed greater rejection for divalent cations (Ca2+, Mg2+) and anions (SO42−) compared to monovalent cations (Na+, K+) and anions (Cl−, NO3−). The degree of total DOC removal was: GAC adsorption + NF (86%) > an ion exchange resin (Purolite) adsorption + NF (81%) > NF operation alone (72%). GAC + NF removed biopolymers and hydrophobic substances almost completely and the highest percentage of LMW neutral substances. In contrast, Purolite + NF almost completely removed humic substances. The degree of membrane fouling order was: LMW neutrals > building blocks > biopolymers > hydrophobics > humics. Adsorption pre-treatment reduced membrane fouling and increased solution flux, the outcome being better with GAC compared to Purolite. Of the 10 MOPs in the MF water, seven were rejected > 90% by NF without any pre-treatment. Conversely, Purolite and GAC pre-treatments rejected > 90% of all OMPs.

Identifying the best coagulant for simultaneous water treatment objectives: Interactions of mononuclear and polynuclear aluminum species with different natural organic matter fractions

As some water utilities are facing increasing concentrations of natural organic matter (NOM) in source water, it has been observed that some of this organic content is refractory to conventional coagulation treatment with alum and ferric sulfate. However, prehydrolyzed coagulants containing polymeric and/or cationic aluminum species such as Al2, Al3, Al13, and Al30 offer many advantages over conventional metal salts, including improved removal of hydrophilic compounds, stronger electrostatic interactions with anionic functional groups, better stability over a wider pH range, etc. Residual NOM after coagulation was characterized using liquid chromatography–organic carbon detection–organic nitrogen detection (LC-OCD-OND), while aluminum species were identified using nuclear magnetic resonance (NMR). Six coagulants having different proportion of Al species were tested on three surface waters, and guidelines for the coagulant selection are proposed for different NOM fractions: humics (HS), building blocks (BB, breakdown products of HS), low molecular weight acids (LMWa), low molecular weight neutral (LMWn) compounds, biopolymers (BP), and dissolved organic nitrogen from the HS fraction (HS-DON). In summary, ferric sulfate outperformed aluminum-based coagulants in acidic conditions (pH < 6) while aluminum chlorohydrate (basicity of 83 %) was repeatedly noted to be the best coagulant in more alkaline conditions (pH > 7). Under more neutral pH (6–7), alum offered a good compromise between DOC and turbidity removals and the coagulant cost. Coagulant performance was also assessed based on typical indicators used in the industry such as turbidity, dissolved organic carbon (DOC), residual aluminum/iron, trihalomethanes/haloacetic acids (THM/HAA) precursors, and alkalinity consumption. Considering all indicators and NOM fractions, this study revealed that PAX 14, a slightly prehydrolyzed coagulant (basicity of 23 %), exhibited the best performance during enhanced coagulation at pH 6.0.

Effects of coagulation-sedimentation-filtration pretreatment on micropollutant abatement by the electro-peroxone process

The electro-peroxone (EP) process has been considered an attractive alternative to conventional ozonation for micropollutant abatement in water treatment. However, how to integrate the EP process into the water treatment trains in water utilities has yet to be investigated. This study compared micropollutant abatement during the EP treatment of potable source water with and without pretreatment of biological oxidation, flocculation, sedimentation, and filtration. Results show that this pretreatment train removed 39% of dissolved organic carbon (DOC) and 28% of the UV254 absorbance of the raw water, leading to higher ozone (O3) stability in the treated water. By electrochemically generating hydrogen peroxide to accelerate O3 decomposition to hydroxyl radicals (•OH), the EP process considerably shortened the time required for ozone depletion and micropollutant abatement during the treatment of both the raw and pretreated water to ∼1 min, compared to ∼3 and 7.5 min during conventional ozonation of the raw and treated water, respectively. For the same specific ozone dose of 1 mg O3 mg−1 DOC (corresponding to 4.3 and 2.8 mg O3 L−1 for the raw and treated water, respectively), the abatement efficiencies of micropollutants with moderate and low ozone reactivity were increased by ∼10–15%, while the energy consumption for micropollutant abatement was decreased by ∼24–56% during the EP treatment of the treated water than the raw water. These results indicate that partial removal of DOC and ammonia from the raw water by the pretreatment train has a beneficial effect on enhancing micropollutant abatement and reducing energy consumption of the EP process. Therefore, it is more cost-effective to integrate the EP process after the pretreatment train in water utilities for micropollutant abatement.

Removal of natural organic matter by ion exchange: Comparing regenerated and non-regenerated columns

Dissolved organic matter (DOM) in water has adverse impacts on the water treatment process and is effectively removed by ion exchange (IEX). Some researchers have proposed the term biological ion exchange (BIEX) for the process of continuous DOM removal by ion exchange without the need for chemical regeneration that results in brine waste. Surface water with moderate dissolved organic carbon (DOC) concentrations (4–6 mg/L) and high sulfate concentrations (80 – 120 mg/L) was fed to two regenerated and two non-regenerated columns for 12,500 bed volumes (9 months) with the goal of investigating the effects of chemical and possibly biological regeneration on long-term IEX operation. Chemically regenerated columns achieved between 60 and 80% DOC removal for the entirety of the experiment, while non-regenerated columns achieved steady DOC removal of ~50%. Inorganic ion analysis showed that biological activity had minimal impact on DOC removal, and the main mechanism of removal was secondary IEX between sulfate (SO42−) and fractions of DOC with high affinities for ion exchange. Fluorescence and specific UV absorbance at 254 nm (SUVA 254) data showed that fractions of DOC with higher SUVA 254 values (terrestrial-like fractions) were better removed by secondary IEX than those with lower SUVA 254 values (aquatic/microbial-like fractions). Scanning electron microscopy showed that biofilms on non-regenerated resins covered 5–15% of the resin surface and are composed of numerous species of bacteria with varying functions, with some protozoa present.

Performance of a lab-scale membrane aerated biofilm reactor treating nitrogen dominant space-based wastewater through simultaneous nitrification-denitrification

A membrane-aerated biofilm reactor (MABR) was designed for the treatment of a source-separated urine wastewater formulated to mimic conditions on an early planetary space habitation. Literature suggested that a MABR would not work effectively for nitrogen removal for this wastewater since it is nitrogen dominant (total organic carbon to nitrogen ratio < 1). The MABR studied in this study confirmed that hypothesis by recording average nitrification and denitrification efficiencies as high as ∼65 % and ∼35 %, respectively. Nonetheless, the simultaneous nitrification and denitrification performance was unexpectedly high when compared to the reactor’s low liquid velocities (0.004 cm/s) and it’s relatively high bulk dissolved oxygen (DO) levels (> 2 mg/L). Dissolved organic carbon (DOC) removal and nitrification rates were reported as high as 0.33 ± 0.12 g-C/m2-d and 0.32 ± 0.02 g-N/m2-d, respectively. Additionally, the MABR achieved total nitrogen (TN) removal efficiency of 36.5 %. Additionally, the operational parameters of hydraulic retention time, intramembrane partial oxygen pressure, recycle ratio and liquid velocity linked with bulk DO concentration were evaluated. It was observed that TN removal was significantly impacted by the variation of those parameters, but DOC removal efficiency and nitrification rate did not change significantly. This study helps to establish the efficacy of MABR systems for the treatment of nitrogen dominant, space-based wastewater.

Removal of disinfection by-product precursors by ion exchange resins

The removal of dissolved organic carbon (DOC) is a key factor in the control of disinfection by-product (DBP) formation in drinking water. Ion exchange process deals with the removal of naturally negatively charged organic matter. A fluidized bed column test has been chosen to test in parallel the efficiency of 4 different anionic exchange resins (Purolite PPA860S, Dowex TAN-1, Amberlite IRA-958 and IRA-410) in terms of DOC fraction removal and related DBP formation reduction. IRA-410 was shown to be the best performing resin in terms of DOC and DBP formation potential reduction followed by PPA860S. These resins removed respectively 41 and 37 % of DOC, with humic substances as the main target of the two resins (68 and 72 % reduction, respectively, based on size exclusion chromatography with an organic carbon detector). The UV absorbance was reduced in a higher proportion than the DOC demonstrating a preference of the resins for the relatively hydrophobic compounds. The reduction in trihalomethane and haloacetic acid formation was higher than the DOC removal for IRA-410 and PPA860S (53 and 59 %, respectively); whereas IRA-958 on the other hand showed a lower reduction in DBP formation potential than its DOC removal. All the resins showed a much higher reduction of iodinated trihalomethanes formation potential (66–96% reduction compared to raw water) due to the removals of iodide in addition of organic precursors. However, in a context of increasing halide concentrations, the different resins showed a reduction of their efficiency to control the formation of DBPs.

Removal Characteristics of Effluent Organic Matter (EfOM) in Pharmaceutical Tailwater by a Combined Coagulation and UV/O3 Process

A novel coagulation combined with UV/O3 process was employed to remove the effluent organic matter (EfOM) from a biotreated pharmaceutical wastewater for harmlessness. The removal behavior of EfOM by UV/O3 process was characterized by synchronous fluorescence spectroscopy (SFS) integrating two-dimensional correlation (2D-COS) and principal component analysis (PCA) technology. The highest dissolved organic carbon (DOC) and ratio of UV254 and DOC (SUVA) removal efficiency reached 55.8% and 68.7% by coagulation-UV/O3 process after 60 min oxidation, respectively. Five main components of pharmaceutical tail wastewater (PTW) were identified by SFS. Spectral analysis revealed that UV/O3 was selective for the removal of different fluorescent components, especially fulvic acid-like fluorescent (FLF) component and humus-like fluorescent (HLF) component. Synchronous fluorescence/UV-visible two-dimensional correlation spectra analysis showed that the degradation of organic matter occurred sequentially in the order of HLF, FLF, microbial humus-like fluorescence component (MHLF), tryptophan-like fluorescent component (TRLF), tyrosine-like fluorescent component (TYLF). The UV/O3 process removed 95.6% of HLF, 80.0% of FLF, 56.0% of TRLF, 50.8% of MHLF and 44.4% of TYLF. Therefore, the coagulation-UV/O3 process was proven to be an attractive way to reduce the environmental risks of PTW.