Organic Carbon Detection Research Articles

Enhanced removal of humic substances in effluent organic matter from a leachate treatment system via biological upgradation of molecular structure

ABSTRACT Biological upgradation (BU) process was proposed, with the goal of converting the molecular structure, for improving the coagulation effect on humic substances (HS) in effluent organic matter from the membrane bioreactor of a leachate treatment system. Enhancement of coagulation effect was observed with the improvement of chemical oxygen demand and HS removal efficiency from 45.5% and 56.5% to 80.0% and 92.6% (Fe dosage was 400 mg·L−1), respectively, which was approximately 30–40% higher than the other available researches. Variations in molecular weight (MW) and carboxyl contents of fulvic acid (FA) and humic acid (HA) were analysed by size exclusion chromatography coupled with dissolved organic carbon detection, potentiometric titration and Fourier transform infrared spectroscopy. The obtained results indicated that BU process led to the growth of MW of HS, of which the larger MW (1650 Da) FA and HA raised from 19.07 and 0.34 mgC·L−1 to 71.67 and 1.58 mgC·L−1, respectively, as well as increases in the carboxyl contents of FA and HA from 6.70 and 6.28 meq·gC−1 to 11.84 and 8.71 meq·gC−1, respectively. Because of this, a stronger binding effect between Fe and HS might be formed that improved the coagulation effect.

Macromolecular Characterization of Compound Selectivity for Oxidation and Oxidative Alterations of Dissolved Organic Matter by Manganese Oxide.

Manganese (Mn) oxides can oxidize dissolved organic matter (DOM) and alter its chemical properties and microbial degradability, but the compound selectivity for oxidation and oxidative alterations remain to be determined. We applied ultrahigh mass spectrometry to catalog the macromolecular composition of Suwannee River fulvic acid (SRFA) before and after oxidation by a Mn oxide (δ-MnO2) at pH 4 or 6. Polycyclic aromatic hydrocarbons, polyphenols, and carbohydrates were more reactive in reducing δ-MnO2 than highly unsaturated and phenolic (HuPh) compounds and aliphatics, but highly abundant HuPh contributed the most (∼50%) to the overall reduction of δ-MnO2. On average, oxidized species had higher molecular weights, aromaticity, carbon unsaturation degree, nominal oxidation state of carbon, and oxygen and nitrogen contents but were lower in hydrogen content compared to unoxidized species. The oxidation decreased these molecular indices and oxygen and nitrogen contents but increased the hydrogen content, with stronger changes at the lower pH. This DOM oxidation on polar mineral surfaces was more selective but shared similar selectivity rules to adsorption. The abiotic oxidation resembles microbial oxidative degradation of organic matter, and Mn oxide-oxidizable carbon may be a useful index for detection and identification of labile organic carbon.

Degradation effect of ultraviolet-induced advanced oxidation of chlorine, chlorine dioxide, and hydrogen peroxide and its impact on coagulation of extracellular organic matter produced by Microcystis aeruginosa

Implementation of an ultraviolet (UV)-induced advanced oxidation process (AOP) before coagulation was found to enhance the removal of algae cells. However, the effect of UV-induced AOPs on extracellular cellular organic matter (EOM) and on its coagulation and removal was neglected. This study investigated the impact of UV-induced AOPs (UV/Cl2, UV/ClO2, and UV/H2O2) on EOM from Microcystis aeruginosa, and its coagulation and removal by a conventional gravity system (CGS), dissolved air flotation, and a low-energy flash-pressurized flotation (FPF) process. The changes in EOM characteristics before and after the UV-induced AOPs were based on UV absorbance (UV254) and liquid chromatography with organic carbon detection analysis. The reduction in UV254 increased with an increasing dose of oxidant and UV irradiation. The reduction in UV254 for UV/Cl2, UV/ClO2 and UV/H2O2 was 59.5%, 26.5%, and 17.5% respectively, for 0.71 mM equimolar concentration of oxidant and 1920 mJ/cm2 UV irradiation, as evident from a pseudo-first order kinetics study. Similarly, degradation of the high molecular weight to low molecular weight (LMW) fraction was pronounced for UV/Cl2. The coagulation efficiency decreased after UV-induced AOP in the following order: UV/H2O2 > UV/ClO2 > UV/Cl2. By contrast, the low-energy FPF process showed a higher removal of LMW fractions than CGS. Thus, low-energy FPF could be an alternative technology for the UV-induced AOP treatment system.

Characterization of marine dissolved organic matter and its effect on ozonation

As the marine industry develops, the importance of seawater treatment process is increasing. To treat seawater, oxidation processes have primarily been used, such as ballast water treatment systems, aquaculture farm operations, aquarium management, and seawater desalination. However, dissolved organic matter in seawater, whose characteristics vary spatially and seasonally, affects the efficiency of oxidation processes. Therefore, in this study, seawater samples were acquired from various locations in the Republic of Korea to understand the spatio-temporal patterns of marine dissolved organic matter. It was reported that the characterization of marine dissolved organic matter using liquid chromatography—organic carbon detector and excitation-emission matrix—parallel factor modeling. Furthermore, the effects of marine dissolved organic matter were evaluated on ozonation, an oxidation process. The results demonstrate that marine dissolved organic matter varies in its aquagenic, pedogenic, and intermediate characteristics based on region and season. These variations affect ozonation by influencing the consumption of oxidants (e.g., bromine). As a result, it was concluded that characterizing marine dissolved organic matter can help improve the effectiveness of oxidation processes, particularly ozonation.

Natural organic matter removal in a full-scale drinking water treatment plant using ClO2 oxidation: Performance of two virgin granular activated carbons

The removal of different natural organic matter (NOM) components from boreal lake water was studied at ambient temperature (0.4–18.5 °C) in a full-scale drinking water treatment plant (DWTP). The specific aim was to compare the performance of granular activated carbon (GAC) filters containing different commercial carbons. Liquid chromatography with organic carbon detection (LC-OCD), fluorescence excitation and emission matrices (FEEM), and biodegradable dissolved organic carbon (BDOC) analyses showed that surface water NOM was dominated by humic substances (HS), had the highest fluorescence intensity at the region associated with fulvic acid-like NOM and contained, on average, 0.2 mg/L of BDOC. Coagulation-flocculation and flotation removed 61–82 % of HS and biopolymers and, on average, 50 % of the BDOC. Chlorine dioxide oxidation increased the proportion of HS with 18–22 % and the concentration of BDOC with, on average, 0.05 mg/L, while it decreased the proportion of low-molecular-weight neutrals (LMWN). Sand and GAC filtration removed BDOC to a level below 0.15 mg/L. The two studied GACs showed a 25 % difference in their cumulative total organic carbon (TOC) removals. The distributions of NOM fractions were similar in the effluents of both filters, with LMWN being the most efficiently removed fraction. NOM removal was due to adsorption rather than biodegradation in the filters. In conclusion, DWTPs benefit from complementary analyses, such as LC-OCD, FEEM and BDOC, for understanding and optimising NOM removal. Comparison of different GACs in full-scale studies is also important due to differences in the TOC removals of GACs with similar product specifications.

Biochemical characteristics and membrane fouling behaviors of soluble microbial products during the lifecycle of Escherichia coli

The complexity of production process and chemical compositions of soluble microbial products (SMPs) largely limits the understanding of membrane fouling in membrane bioreactors (MBRs). Herein, we used a model single-strain Escherichia coli to better understand the chemical natures of SMPs and their roles in membrane fouling. The effects of carbon source and growth phase on the chemical compositions of SMPs were identified at both the compound and molecular levels by using advanced techniques including excitation emission matrix and parallel factor analysis (EEM-PARAFAC), size exclusion chromatography coupled with organic carbon detection (LC-OCD), and untargeted ultra-performance liquid chromatography - Q-Exactive - mass spectrometry (UPLC-Q-Exactive-MS). Subsequently, the roles of SMPs in the propensity of membrane fouling during ultrafiltration (UF) were studied. The results showed that the chemical compositions and fouling potentials of SMPs were carbon source- and growth phase-dependent. In the exponential phase, SMPs mainly consisted of utilization-associated products (UAPs) and remaining substrates. As the microorganism progressed into the stationary and senescent phases, UAPs and biomass-associated products (BAPs) were the main components, respectively. The SMP contents generated in glucose medium were higher than those generated in acetate medium, and higher abundances of humic fluorescent components were observed in glucose-fed SMPs. Van Krevelen diagrams of the UPLC-MS results revealed that acetate-fed SMPs contained more carboxylic-rich alicyclic molecules, peptides-like, aromatic, and carbohydrates-like components than glucose-fed SMPs in the stationary and senescent phases. These components played a significant role in irreversible membrane fouling, as evidenced in UF experiments. Standard blocking and cake filtration were the main fouling mechanisms for the filtration of SMPs collected in the exponential and stationary/senescent phases, respectively. Our findings highlight linkages between SMP compositions and membrane fouling at both the compound and molecular levels and suggest that both the carbon source and growth phase strongly determine the production potential, chemical nature, and fouling behavior of SMPs.

Selective quantification of nanoplastics in environmental matrices by asymmetric flow field-flow fractionation with total organic carbon detection.

Nanoplastics are of rapidly emerging concern as ubiquitous environmental pollutants. However, fate and transport assessments are currently hindered by a need for new analytical methods that can selectively quantify nanoplastics in environmental matrices. This study presents the first proof of principle to hyphenate asymmetric flow field-flow fractionation (AF4) with total organic carbon (TOC) detection for nanoplastics analysis, as evaluated on mixtures of multimodal polystyrene nanoplastics in the presence of dissolved organic matter and clay colloids. The AF4-TOC method enables more robust, size-resolved quantification of nanoplastics over other AF4 detection modes, including UV-vis, refractive index, and fluorescence tagging. This method development can fill a critical gap in analytical methodology for environmental nanoplastics research.

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.

Monitoring Biofouling Potential Using ATP-Based Bacterial Growth Potential in SWRO Pre-Treatment of a Full-Scale Plant.

Several potential growth methods have been developed to monitor biological/organic fouling potential in seawater reverse osmosis (SWRO), but to date the correlation between these methods and biofouling of SWRO has not been demonstrated. In this research, the relation between a new adenosine triphosphate (ATP)-based bacterial growth potential (BGP) test of SWRO feed water and SWRO membrane performance is investigated. For this purpose, the pre-treatment of a full-scale SWRO plant including dissolved air flotation (DAF) and two stage dual media filtration (DMF) was monitored for 5 months using BGP, orthophosphate, organic fractions by liquid chromatography coupled with organic carbon detection (LC-OCD), silt density index (SDI), and modified fouling index (MFI). Results showed that particulate fouling potential was well controlled through the SWRO pre-treatment as the measured SDI and MFI in the SWRO feed water were below the recommended values. DAF in combination with coagulation (1–5 mg-Fe3+/L) consistently achieved 70% removal of orthophosphate, 50% removal of BGP, 25% removal of biopolymers, and 10% removal of humic substances. Higher BGP (100–950 µg-C/L) in the SWRO feed water corresponded to a higher normalized pressure drop in the SWRO, suggesting the applicability of using BGP as a biofouling indicator in SWRO systems. However, to validate this conclusion, more SWRO plants with different pre-treatment systems need to be monitored for longer periods of time.

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.

Characterisation of groundwater dissolved organic matter using LC[sbnd]OCD: Implications for water treatment

The polarity and molecular weight of dissolved organic matter (DOM) is an important factor determining the treatability of water for domestic supply. DOM in surface water and groundwater is comprised of a mixture of carbon with varying molecular weight ranges, with its composition driven by DOM sources and processing. Here, we present the largest dataset of chromatographic DOM in surface and groundwater samples (n = 246) using liquid chromatography organic carbon detection (LCOCD). Our data represents four categories (surface water, hyporheic zone water, local groundwater, and regional groundwater) from five different sites across Australia. In all environments, high molecular weight hydrophilic DOM such as biopolymers (BP) and humic substances (HS) are present in surface waters and are processed out of groundwater as it moves from surface water and hyporheic zones into shallow local groundwater and deeper regional groundwaters. This results in a higher percentage of low molecular weight neutrals (LMWN) and hydrophobic organic carbon (HOC) in deeper regional groundwaters. Our findings indicate that the presence of sedimentary organic matter strongly influence the character of surface and groundwater DOM, resulting in groundwater with higher HS aromaticity and molecular weight, and reduced percentage of LMWNs. We also observe highly variable hydrophilic / HOC ratios in groundwater at all sites, with 9.60% and 25.64% of samples at sites containing sedimentary peat layers and non-sedimentary peat sites respectively containing only hydrophilic dissolved organic carbon (DOC). We identify average hydrophilic / HOC ratios of 4.35 ± 3.76 and 7.53 ± 5.32 at sites containing sedimentary peat layers and non-sedimentary peat sites respectively where both hydrophilic DOC and HOC are present. Overall our results suggest that fractured rock and alluvial aquifers in sedimentary organic carbon poor environments may contain DOC which is better suited to ozonation, biologically activated carbon filtration powdered activated carbon, suspended ion exchange treatment or magnetic ion exchange resin since DOC is more hydrophilic and of lower molecular weight and lower aromaticity. Aquifers located near sedimentary organic matter layers may benefit from pre-treatment by coagulation/flocculation, sedimentation and sand filtration which have high removal efficiency for high molecular weight and polar compounds.

Sorptive removal of disinfection by-product precursors from UK lowland surface waters: Impact of molecular weight and bromide

The current study compared the impact of three different unit processes, coagulation, granular activated carbon (GAC), and a novel suspended ion exchange (SIX) technology, on disinfection by-product formation potential (DBPFP) from two UK lowland water sources with medium to high bromide content. Specific attention was given to the influence of the organic molecular weight (MW) fraction on DBPFP as well as the impact of bromide concentration. Whilst few studies have investigated the impact of MW fractions from Liquid Chromatography with Organic Carbon Detection (LC-OCD) analysis on dissolved organic carbon (DOC) removal by different processes, none have studied the influence of DOC MW fractions from this analysis on DBP formation. The impact of higher bromide concentration was to decrease the total trihalomethane (THM) and haloacetic acid (HAA) mass concentration, in contrast to previously reported studies. Results indicated that for a moderate bromide concentration source (135 μg/L), the THM formation potential was reduced by 22% or 64% after coagulation or SIX treatment, respectively. For a high bromide content source (210 μg/L), the THM formation potential removal was 47% or 69% following GAC or SIX treatment, respectively. The trend was the same for HAAs, albeit with greater differences between the two processes/feedwaters with reference to overall removal. A statistical analysis indicated that organic matter of MW > 350 g/mol had a significant impact on DBPFP. A multiple linear regression of the MW fractions against DBPFP showed a strong correlation (R2 between 0.90 and 0.93), indicating that LC-OCD analysis alone could be used to predict DBP formation with reasonable accuracy, and offering the potential for rapid risk assessment of water sources.

Removal of Bacteria and Organic Carbon by an Integrated Ultrafiltration-Nanofiltration Desalination Pilot Plant.

Fouling caused by organic matter and bacteria remains a significant challenge for the membrane-based desalination industry. Fouling decreases the permeate quality and membrane performance and also increases energy demands. Here, we quantified the amount of organic matter and bacteria at several stages along the water-treatment train of an integrated ultrafiltration–nanofiltration seawater treatment pilot plant. We quantified the organic matter, in terms of Total Organic Carbon (TOC) and Assimilable Organic Carbon (AOC), and evaluated its composition using Liquid Chromatography for Organic Carbon Detection (LC-OCD). The bacterial cells were counted using Bactiquant. We found that ultrafiltration (UF) was effective at removing bacterial cells (99.7%) but not TOC. By contrast, nanofiltration (NF) successfully removed both TOC (95%) and bacterial cells. However, the NF permeate showed higher amounts of AOC than seawater. LC-OCD analysis suggested that the AOC was mostly composed of low molecular weight neutral substances. Furthermore, we found that the cleaning of the UF membrane using chemically enhanced backwash reduced the amount of AOC released into the UF permeate. By implementing the cleaning-in-place of the NF membrane, the pressure drop was restored to the normal level. Our results show that the UF and NF membrane cleaning regimes investigated in this study improved membrane performance. However, AOC remained the hardest-to-treat fraction of organic carbon. AOC should, therefore, be monitored closely and regularly to mitigate biofouling in downstream processes.

Organics removal in high strength petrochemical wastewater with combined microbubble-catalytic ozonation process

Ozonation is a well-known and widely applied advanced oxidation process (AOP) for industrial wastewater treatment, while the ozonation efficiency might be limited by low mass transfer, poor solubility, and rapid decomposition rate of ozone molecules in the aqueous phase. The present study aims to investigate the feasibility of combined microbubble-catalytic ozonation process (M-O3/Fe/GAC) for improving the ozonation efficiency during treatment of petrochemical wastewater (PCW). M-O3/Fe/GAC process optimization was carried out with different pH conditions, ozone dosages and catalyst loadings. The optimum operating conditions were identified as 50 mg L−1 ozone dosage, real PCW pH (7.0–7.5) and 4 g L−1 catalyst loading. Among different ozonation processes, M-O3/Fe/GAC process achieved the highest chemical oxidation demand (COD) removal efficiency of 88%, which is 18% and 43% higher than those achieved by the microbubble and macrobubble ozonation processes, respectively. Phenolic compounds presented in PCW could be reduced by 63% within 15 min in M-O3/Fe/GAC treatment process. Long-term continuous flow studies suggested M-O3/Fe/GAC process to be the most cost-effective technology for PCW treatment with an operating cost of S$0.18 kg−1 COD and S$0.4 m-3 with good catalyst stability. Liquid size exclusion chromatography with organic carbon detection (LC-OCD) data suggested humic substances to be the dominant organic species in PCW, M-O3/Fe/GAC could achieve significant humic substances removal and biodegradability enhancement in PCW. Kinetics and mechanism studies revealed that organics removal in M-O3/Fe/GAC was 1.8 times higher than that in microbubble ozonation process, and hydroxyl radical (●OH) was the dominant oxidant specie for organics removal in M-O3/Fe/GAC process.

Assimilable organic carbon removal strategy for aquifer storage and recovery applications

Aquifer storage and recovery (ASR) technology has been adopted as a strategic water management tool. However, during the injection of oxic and organic carbon-containing water to the underground aquifers, severe phenomena such as clogging and groundwater deterioration have been reported. To prevent these severe phenomena, assimilable organic carbon (AOC) concentration has been controlled in the ASR applications by supporting bacteria growth potential. In this study, the AOC removal strategy was investigated in a simulated ASR system using an indigenous bacterium, Pseudomonas jinjuensis. AOC removal was evaluated under three different experimental conditions: (i) 30 °C and aerobic, (ii) 15 °C and aerobic, and (iii) 15 °C and anoxic. The effects of contact media such as sand and granular activated carbon on AOC removal efficiency were also investigated. Results show that under the 30 °C aerobic condition, P. jinjuensis could remove 99.8% (13 μg L−1) of AOC with soil. The variations in the organic fractions determined by liquid chromatography with organic carbon detector analysis were observed and showed trends similar to those of AOC determined by the flow cytometry method. The indirect injection method in ASR application was recommended due to the AOC removal benefit by soil indigenous bacterium.

Assessing the performance of membrane photobioreactors (MPBR) for polishing effluents containing different types of nitrogen

Membrane photobioreactors (MPBR) have the opportunity to remove various forms of nitrogen, such as ammonium and nitrate, found in high quantities in secondary effluent. This study provides a holistic comparison of the performance of two membrane photobioreactors treating secondary effluents containing ammonium (NH4+-N) or nitrate (NO3−-N) as the sole nitrogen source. Sophisticated analyses, such as flow cytometry, polymerase chain reaction denaturing gradient gel electrophoresis, liquid chromatography – organic carbon detection analysis and fluorescence excitation-emission matrix spectroscopy, were used to provide insight into system characteristics and performance. In terms of treatment efficiency, NH4+-N was better removed from the system (by 56%) compared to NO3−-N (33%). The MPBR fed with NH4+-N produced less microalgal cells (4.4 × 107 cells/ml compared to 5.3 × 107 cells/ml in that treating NO3−-N) but higher proportion of bacteria (6.3% compared to 2.1%), leading to a higher system heterogeneity. The biomass produced from the MPBR treating NH4+-N featured a higher level of extracellular materials and a lower dewaterability (as suggested by a significantly higher capillary suction time of 25.2 s than 13.1 s observed for the culture grown on NO3−-N), indicating a lower harvesting potential. As a result, faster membrane fouling was observed when NH4+-N was fed. This leads to a recommendation that operating conditions are optimised dependent on the form of nitrogen that needs to be treated.

Characterisation of microalgae-based monocultures and mixed cultures for biomass production and wastewater treatment

Microalgae-based systems have been increasingly considered to remediate wastewater, while producing valued biomass. While microalgal monocultures are difficult to maintain in wastewater, mixed cultures have the potential to offer improved system stability and robustness. This research aims to provide a detailed comparison of microalgal monoculture and mixed culture photobioreactors (PBRs) in terms of microalgae growth, biomass harvesting potential, nutrient removal and organic characteristics. Some of the PBRs were further tested for their responses to the presence of wastewater-derived bacteria. Monocultures (containing species from Chlorophyta, Cyanophyta and Eustigmatophyta, respectively) and mixed cultures (mixing two or three species) were evaluated using advanced characterisation techniques including flow cytometry, liquid chromatography – organic carbon detection and excitation−emission matrix fluorescence spectroscopy. The impact of bacteria on system performance was explored by co-culturing some of the cultures with activated sludge. In general, mixed culture systems showed more stable biomass growth and improved nutrient removal uptake (by 20%), as compared to monocultures. However, overyielding (higher biomass production) was not observed in the mixed cultures. Mixing different microalgae tended to increase the concentrations of soluble extracellular materials (e.g. biopolymers) that were able to retain water within the biomass, leading to a lower biomass harvesting potential, as indicated by the capillary suction time. Adding activate sludge significantly increased reduction of measurable dissolved organic carbon concentration (particularly biopolymers and low molecular weight compounds) and nitrogen by >250%. However, wastewater-derived bacteria reduced the yield of all the cultures substantially (by 63–76%) and lowered the dewaterability of the cultures.

Colloidal iron and organic carbon control soil aggregate formation and stability in arable Luvisols

Several beneficial soil functions are linked to aggregates, but how the formation and stability depend on the presence of colloidal- and nanosized (1000–1 nm) bulding blocks is still understood poorly. Here, we sampled subsites from an arable toposequence with 190 and 340 g kg−1 clay, and isolated small soil microaggregates (SMA; <20 µm) from larger macroaggregate units (>250 µm) using an ultrasonic dispersion energy of 60, 250, and 440 J mL−1, respectively. We then allowed these small SMA to reaggregated after chemical removal of organic carbon (OC) as well as of Fe- and Al (hydr)oxides, respectively. The size distribution of the reaggregated small SMA and fine colloids (<0.45 µm) was analyzed via laser diffraction and asymmetric flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry and organic carbon detection, respectively. We found elevated amounts of both finer colloids and stable SMA at subsites with higher clay contents. The size distribution of small SMA was composed of two distinctive fractions including colloids and larger microaggregates with an average size of 5 µm. The removal of Fe with Dithionite-Citrate-Bicarbonate (DCB) shifted the size of the small SMA to a larger equivalent diameter, while removal of OC with NaOCl reduced it. After three wetting and drying cycles, the concentration of colloids declined, whereas the small SMA without chemical pre-treatments reaggregated to particles with larger average diameters up to 10 µm, with the size depending on the clay content. Intriguingly, this gain in size was more pronounced after Fe removal, but it was not affected by OC removal. We suggest that Fe (hydr)oxides impacts the stability of small SMA primarily by being present in small-sized pores and thus cementing the aggregates to smaller size. In contrast, the effect of OC was restricted to the size of colloids, gluing them together to small SMAs within defined size ranges when OC was present but releasing these colloids when OC was absent.

Organic matter from biofilter nitrification by high performance size exclusion chromatography and fluorescence excitation-emission matrix.

A combination of high performance size exclusion chromatography with organic carbon detector and ultraviolet detector coupled with peak-fitting technique and fluorescence excitation-emission matrix spectrometry applied fluorescence regional integration method was conducted to determine the characteristics of organic matter during nitrification. The batch scale of bionet nitrification without organic carbon substrate under aerobic conditions was operated for around 150 minutes. Bulk organic parameters and NH4+-N concentration were analyzed. Five different molecular weights of organic matter were identified by using chromatography, and five different groups of fluorophores organic fractions detected by fluorescence. According to chromatography with carbon and ultraviolet detector, the main characteristics of organic matter shifted from building blocks aromatic compounds with percentage peak area of carbon/ultraviolet detector: 31%/53% to 14%/27.5% to humic-like substances with percentage peak area of carbon/ultraviolet detector 21%/17% to 27%/46.5% during nitrification. Those former compounds are biodegradable as well as properties of microbial products released during substrate utilization and endogenous phase, which are mainly identified as humic-like substances, thus underwent further biodegradation. However, there was significant change in the fluorophores organic fractions, which exhibited humic acid-like with percentage fluorescence regional index area 53% into 68%, as shown by fluorescence excitation-emission matrix analysis. A combination of these methods indicated that the organic matter released during nitrification mainly consists of humic compounds. These results conjecture that a combination of high performance size exclusion chromatography with carbon and ultraviolet detector and fluorescence excitation-emission matrix can be used to determine the characteristic of organic matter and water quality change during nitrification.

Evaluation the Use of the lux Reporter System pUC19-luxAB for Rapid and Sensitive Detection of Assimilable Organic Carbon (AOC) in Reverse Osmosis (RO) Feed Water

Evaluation the Use of the lux Reporter System pUC19-luxAB for Rapid and Sensitive Detection of Assimilable Organic Carbon (AOC) in Reverse Osmosis (RO) Feed Water