Concentrations Of Humic Substances Research Articles

Influence of land‐use changes on microbial community structure and diversity in a semiarid region

AbstractLand‐use change and the conversion of land into croplands is one of the main drivers of soil degradation and the loss of soil organic carbon. Few studies have evaluated the impact of the expansion of the agricultural frontier on soil microbial communities in the Gran Chaco region in South America; therefore, the objective of this study was to explore how soil microbial communities respond to land‐use changes in a semiarid region of Argentina. The land uses selected were total and selective clearing with livestock (TC‐livestock and SC‐livestock), total clearing with agriculture (TC‐agriculture), and an undisturbed site (R‐Chancaní). Our results suggest that microbial abundances were strongly influenced by seasonal changes. In both seasons, the lowest values of total microbial biomass were observed in TC‐agriculture and TC‐livestock. In the wet season, TC‐agriculture had the lowest fungal abundance, and both total clearing sites (TC‐livestock and TC‐agriculture) had higher bacterial abundance than the other sites. Our data also showed that the Shannon and richness indices were highest at the farming sites, indicating a similar tendency in the diversity indexes in both dry and wet seasons. According to Pearson correlation analysis, humic substance (HS) content was a key driver influencing soil microbial communities, demonstrating that high HS content may significantly increase bacteria, fungi, and total phospholipid fatty acids. Microbial composition highly depended on seasonal changes. Overall, our results suggest that land‐use change altered microbial community structure and bacterial diversity, and that HS content played a crucial role in driving changes in soil microbial composition.

Insights into the properties of surface waters and their associated nanofiltration membrane fouling: The importance of biopolymers and high molecular weight humics

Nanofiltration (NF) membrane fouling by surface waters is still an unclear and unpredictable topic due to the heterogeneity and variability of natural organic matter (NOM) in waters. The objective of this study was to identify the key water quality parameter/s responsible for NF membrane fouling. Six representative surface waters were systematically investigated in terms of the water quality characteristics and their fouling potential on a polyamide NF membrane. The results showed that these waters exhibited significant discrepancies in DOC, Ca2+, composition, and chemical characteristics of NOM. Removal performance and membrane fouling analysis indicated a preferential rejection of hydrophobic over hydrophilic NOM, and the hydrophobicity of NOM was positively correlated with reversible fouling. The biopolymer content exhibited a strong positive correlation to the total membrane fouling and irreversible fouling, indicating that it could be used as a surrogate of NF fouling behaviors by surface waters. Ca2+ and humic substances contents could not explain the membrane fouling due to their insignificant correlation with membrane fouling. However, the proportion of high molecular weight component in humic substances (%-HMW) exhibited a negative correlation with the total membrane fouling and irreversible fouling, suggesting that the HMW component has a positive effect on NF membrane fouling prevention. A reasonable explanation is that the HMW component is preferentially deposited on the membrane surface, forming a ‘controlling layer’ that prevents low MW organics from entering and blocking the membrane pores.

Fertigation of humic substance: effects on soil properties of a xanthic ferralsol (DENSIC)

The complexity of humic substances (HS) and their properties in agricultural applications have attracted the attention of many researchers. However, controversial results have been obtained, because of the difficulty in identifying a precise relationship between the structure and activity of these substances. This study aimed to evaluate the influence of different frequencies and concentrations of humic substances on the behavior of physical, chemical and microbiological soil attributes. The experiment was carried out at Embrapa Cassava and Fruticulture in Latossolo Amarelo Distrocoeso [(Xanthic Ferralsol (Densic); Oxisol], with a completely randomized block design with four repetitions in a split-plot scheme, with three application frequencies (F1 = 15 days, F2 = 30 days and F3 = 45 days) and four concentrations of humic substances (C1 = 0 ml.L-1, C2 = 3 ml.L-1, C3 = 6 ml.L-1 and C4 = 9 ml.L-1). The humic substance applied at a frequency of 45 days positively favored the physical and chemical attributes of the soil, mainly at concentrations of 6 and 9 ml.L-1, due to the increase in microporosity. This information can be used to improve the performance of agricultural practices, especially those related to soil preparation, use of agricultural inputs, water management, soil water content and, especially, soil management practices.

Effect of humic acid on the growth of seedling tomato (Solanum lycopersicum) and melon Cucumis melo)

This study evaluated the effect of HS extracted from mineral coal on the growth of tomato (Solanum lycopersicum) and melon (Cucumis melo) plants to determine the role that humic substances (HS) play as promoters of plant growth. Three concentrations of HS were evaluated in 200 grams of soil. The fertilizer (urea 0.3%) and humic acid in concentrations of 0.05%, 0.1%, and 0.2% were added directly and at the same time to the amount of soil, using a control sample without the addition of humic acid. Increase measurements were made at three-day intervals up to 45 days. Plants treated with high concentrations of HS demonstrated a significant increase in roots (p>0.05). In both plants, the concentration of 0.2% in HS showed the greatest increase in growth, with the melon plant showing the greatest variation as time passed, with its highest peak in 36 days (13.1 ± 0.05cm) of the experiment, while in the tomato plant the maximum growth occurred in 30 days (9.2 ± 0.01 cm). The Dunnett test showed that there was no statistically significant difference between the control and the concentrations of 0.05% and 0.1% (p>0.05), while among the control and the soil sample with a concentration of 0.2% there was a statistically significant difference (p<0.05). The results show a notable influence of humic acid on the growth of the studied plants, especially at high concentrations.
 Keywords: fertilizer, horticulture, humic acid, soils.

Investigation of Hybrid Modification of Eco-Friendly Polymers by Humic Substances

Research on investigation of hybrid eco-friendly polymers modificated by humic substances are given in this article. The purpose of the research is to investigate a hybrid modification of eco-friendly polymers of polylactic acid by humic substances, it was found that the mechanism of hybrid modification in the matrix synthesis of the polylactic acid-humic substances system indicates an intermolecular bond between polylactic acid and humic substances, at the same time, due to increased crystallization and the emergence of intermolecular and ester bonds in the formation of more rigid mesh structure in the system polylactic acid-humic substances is increasing the mechanical properties of such materials. It was found that the increase in the impact strength and the breaking stress during bending in the polylactic acid-humic substances system in the hybrid modification occurs, while the optimal content of humic substances in the polylactic acid-humic substances systems is 0.5 % by mass.

Use of high-frequency ultrasound to intensify the sorption of humic substances from brines

To intensify the sorption concentration of humic substances from sodium chloride brines, the use of high-frequency ultrasound has been proposed. The optimal parameters of ultrasound were experimentally established as follows: frequency of 11.0–12.0 MHz, sound intensity of 7.5–8.5 W/cm2, and duration of action not less than 2.0 min. Under the action of high-frequency ultrasound as compared to the use of low-frequency ultrasound, the degree of extraction of humic substances from brines with a concentration of sodium chloride of 150 g/l increases from 91.3–93.2% to 97.3–98.2% and from 93.2–95.0% to 98.1–99.0% on wofatit sorbent and diethylaminoethyl cellulose sorbent, respectively. In addition, the effect of high-frequency ultrasound allows quantitatively sorbing humic substances from more concentrated brines (degree of extraction 90%). Moreover, quantitative sorption of humic substances is possible up to a concentration of sodium chloride of 200 g/l and 250 g/l on the wofatit sorbent and diethylaminoethyl cellulose sorbent, respectively. We developed a method for spectrophotometric determination of the content of humic substances in brines with the lower limits of determination of 0.002 mg/l and 0.001 mg/l for humic acids and fulvic acids, respectively.

Performance of watermelon seedlings under the effect of different concentrations of humic substances in the Semi-arid Northeastern Region

Performance of watermelon seedlings under the effect of different concentrations of humic substances in the Semi-arid Northeastern Region

Can the biological stage of a mechanical–biological treatment plant that is designed for mixed municipal solid waste be successfully utilized for effective composting of selectively collected biowaste?

Although the requirements for overall recycling rates can only be met when organic recycling is not overlooked, information is scarce regarding adaption to biowaste composting of existing mechanical–biological treatment (MBT) plants originally designed for stabilization of organic municipal solid waste (OFMSW). Thus, this study aimed to assess the suitability of the operational conditions in the biological part of a full-scale MBT plant now used for stabilization of OFMSW (working line: closed-module–covered-pile–open-pile) with a view to producing compost from biowaste. Temperatures above 75 °C were maintained in the closed module and reached again in the covered pile, indicating that intensive organic-matter mineralization occurred in both stages. In the covered pile, the temperature sharply decreased, indicating depletion of easily biodegradable organic matter. An aerobic 4-day respiration test (AT4) value below 10 mg O2/g dry matter, the cut-off for assessing compost stability, was obtained after 8 weeks. However, a high content of humic substances (HS), reflecting compost maturity, was obtained only after 120 days. The increase in HS content proceeded in two phases. In the first phase (45–84 day), the rate constant and the rate of HS formation were lower than in the second phase (84–120 day) (0.072 vs. 0.087 day−1, 1.97 vs. 3.06 mg C/(g organic matter·d)). All the above-mentioned indicators and the nutrient content (N, P, K, Mg, Ca) in the compost indicates that the biological stage of an MBT plant can successfully treat biowaste. This is in accordance with a circular economy and will contribute to increasing recycling rates.

Quantitative study on the structure-bioavailability relationship of dissolved organic nitrogen in wastewater treatment plant effluent.

This study systematically investigated the relationship between the structure properties and biological characteristics of dissolved organic nitrogen (DON) in the effluents from municipal wastewater treatment plants. Ultrafiltration, Fourier transform infrared (FTIR) spectroscopy, ultraviolet (UV) spectroscopy, and excitation-emission matrix (EEM) fluorescence spectroscopy were used to characterize the structure of organic matters in the effluent samples, and the bioavailability of DON was determined by algal/bacterial-based bioassay. The quantitative analysis of EEM spectra conducted by fluorescence regional integration method showed that the organic portion of all samples was mainly consistent with fulvic acid and protein. Combined with the bioassay results, a positive correlation between the DON bioavailability and the protein content (sum of region I and region II) (r = 0.80, P < 0.02) and soluble microbial byproduct-like materials (region IV) (r = 0.76, P < 0.03) were observed. Nevertheless, the humic substances content represented by the region III and V would negatively affect the DON bioavailability. High humification degree (high HIX value) (r = - 0.77, P < 0.03) was related to low bioavailability. Furthermore, according to UV spectroscopy results, strong aromaticity (high UV254 values) (r = - 0.78, P < 0.03) suggested low DON bioavailability. One protein-like component (C3) and two humic-like components (C1 and C2) were identified via fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC), and component C3 values were positively correlated to the BAN/DON ratio (r = 0.74, P < 0.03). The ultrafiltration showed that the low molecular weight DON (< 3kDa) accounted for 30-73% of the total DON, and no notable relationship was observed for DON molecular weight and its bioavailability.

Changes in Relationships between Humic Substances and Soil Structure following Different Mineral Fertilization of Vitis vinifera L. in Slovakia

The quantity and quality of soil organic matter (SOM) depending on many edaphic and environmental factors may change in response to agriculture-related practices. The SOM humification process can be supported by the application of mineral fertilizers, but in the production vineyards, such information is lacking. NPK fertilizer alters the soil quality, and therefore, the aim of this study was to: (1) assess the extent and dynamics of different NPK (control—no fertilization; 1st NPK; and 3rd NPK levels) rates to the soil with grass sward cover in a productive vineyard on changes in SOM, humic substances (HS), and soil structure, and (2) identify relationships between SOM, HS, and soil structure. Results showed that the share of humic acids in soil organic carbon decreased only in NPK1 compared to control and NPK3 treatments. The color quotient of humic substance values in NPK1 and NPK3 increased by 4 and 5%, respectively, compared to control. Over a period of 14 years, the content of soil organic carbon increased by 0.71, 0.69, and 0.53 g kg−1 year−1 in the control, NPK1, and NPK3, respectively. The content of HS increased linearly with slight differences due to NPK application. The vulnerability of the soil structure decreased due to fertilization—more at the higher NPK level. The rate of formed soil crust was decreasing in the following order: control &gt; NPK1 &gt; NPK3. In the control treatment, the relations between SOM, HS, and soil structure were most abundant and with the greatest significance, while with the increasing level of NPK, these relations lost their significance.

Enhanced hydrolytic removal of tylosin in wastewater using polymer-based solid acid catalysts converted from polystyrene

Antibiotic production wastewater usually contains high concentrations of antibiotic residues, which can cause instability and deterioration of biological wastewater treatment units and also domestication and proliferation of antibiotic-resistance bacteria. An effective pretreatment on antibiotics production wastewater is expected to selectively reduce the concentration of antibiotics and decrease the toxicity, rather than mitigate organic and other contaminants before further treatments. In this work, two polymer-based solid acids, PS-S and CPS-S bearing high concentrations of -SOH3 groups (up to 4.57 mmol/g), were prepared and successfully used for hydrolytic mitigation of 100 mg/L tylosin within 20 min. The co-existence of high concentrations of COD and humic substances did not affect the mitigation of tylosin obviously, while more than 500 mg/L of nitrogenous compounds suppressed the hydrolytic efficiency. Recycle and reuse experiments showed that the solid acids performed well in five cycles after regeneration. Three transformation products (P1, P2 and P3) were identified using UPLC-QTOF-MS/MS. Sugar moieties including mycarse, mycaminose, and mycinose detached and released simultaneously or in order from the 16-member lactone ring through desugarization, which led to a dramatic decrease in antibacterial activity as revealed by cytotoxicity evaluations using S. aureus. Ecotoxicity estimation indicated the acute toxicities of the hydrolyzed products to model species (e.g., fish, daphnid and green algae) were classified as “not harmful”. This work suggested an effective and selective method to pretreat tylosin-contained production wastewater by using polymer-based solid acids. These results will shed light on effective elimination of antibiotics pollution from pharmaceutical industries through strengthening the pretreatments.

Reduced pH is the primary factor promoting humic acid formation during hyperthermophilic pretreatment composting

Hyperthermophilic pretreatment composting (HPC) has the advantages of enhanced composting efficiency and accelerated humic substance (HS) over conventional composting (CC). However, the mechanisms towards the accelerated humification process by HPC are still not clear. By means of sterilization technology, the roles of abiotic and biotic components on the formation of HS can be distinguished. The study investigated the humification degree and the succession of microbial community during HPC of pig manure. The mechanisms underlying the accelerated humification by HPC was identified using gamma sterilization. Results showed that HS content increased significantly by 13.72% in HPC and 29.93% in sterilized HPC inoculated with 1% CC (HPC_I), compared with 8.76% increase in CC and 7.12% increase in sterilized CC inoculated with 1% HPC during composting (CC_I). Compared with CC and CC_I, stronger intensities of HA-like and fulvic acid-like components were observed in HPC and HPC_I. Results showed that physicochemical properties, especially pH, were the key factors in accelerating the humification in HPC, while both physicochemical properties and microbial community contributed to the HA formation in CC. The study contributed to a better understanding of the mechanism towards the accelerated humification degree in HPC.

Enhancement effects of dissolved organic matter leached from sewage sludge on microbial reduction and immobilization of Cr(VI) by Geobacter sulfurreducens

Sewage sludge has a high concentration of dissolved organic matter (DOM) which contains compounds that can serve as electron donors or shuttles for metal reduction by dissimilatory metal reducing bacteria (DMRB). In this study, Cr(VI) removal by G. sulfurreducens, a common DMRB present in anaerobic soils, was examined in the presence or absence of sludge DOM. Two different types of sludge DOM were tested; composted sludge DOM (C-DOM) and anaerobically digested sludge DOM (A-DOM). Both sludge DOMs enhanced Cr(VI) reduction by G. sulfurreducens, but C-DOM was more effective likely because it had higher concentrations of humic substances that served as electron shuttles. Transcriptomic studies indicated that G. sulfurreducens utilizes several different mechanisms to tolerate chromium including extracellular Cr(VI) reduction and immobilization by outer membrane c-type cytochromes and electrically conductive pili, intracellular Cr(VI) reduction by triheme cytochromes and NAD(P)H FMN reductase proteins, and chromium efflux by several P-type ATPase and RND transporter proteins. Microscopy experiments also showed that Cr(III) crystals formed on the surface of the cells, indicating that extracellular Cr(VI) reduction and adsorption was involved in the chromium removal process. These results help provide insight into the potential use of sewage sludge as an additive to enhance the bioremediation of chromium contaminated soils.

The Central Role of Soil Organic Matter in Soil Fertility and Carbon Storage

The aim of the paper is to give an overview on the chemistry of soil organic carbon (SOC) affecting nutrient availability, the emission of greenhouse gases and detoxifying harmful substances in soil. Humic substances represent the stable part of SOC, accounting for between 50 and more than 80% of organically bound carbon in soil. Humic substances strongly affect the soil solution concentration of several plant nutrients and may increase P-, Fe-, and Cu- solubility, thereby increasing their plant availability. Soil organic carbon, mainly humic substances, can detoxify monomeric Al in acid soils, can strongly bind toxic heavy metals, making them unavailable to the plant roots, and may strongly bind a vast variety of harmful organic pollutants. Increasing SOC is an important goal in agriculture. The inclusion of mixtures of semi-perennial plant species and cultivars may strongly increase SOC and humic substance content in soils. To increase SOC, farmyard manure and its rotted or composted forms are superior compared to the separate application of straw and slurry to soil. The storage of carbon, mainly in organic form, in soils is very important in the context of the emission of greenhouse gases. Worldwide, soils release about 10 times more greenhouse gases compared to fossil fuel combustion. Small increments in SOC worldwide will strongly affect the concentration of atmospheric CO2. The public discussion on soil fertility and greenhouse gas emissionshas been politically controlled in a way that leaves the important and positive contribution of soil organic carbon and mainly humic substances partly misinterpreted and partly underestimated.

Sustainable Treatment and Resource Recovery of Anion Exchange Spent Brine by Pilot-Scale Electrodialysis and Ultrafiltration.

The anion exchange (AIX) spent brine, generated during the NDMP-3 resin regeneration process, highly loaded with organic substances mainly humic substances (HSs) and salts (mainly NaCl) remains an environmental concern. In this study, pilot-scale electro dialysis (ED) and ultrafiltration (UF) hybrid technologies were first used to recover NaCl solution as a resin regeneration agent and HSs, which could be utilized as a vital ingredient of organic fertilizer, from the AIX spent brine. Recovered ≈ 15% w/w NaCl solution obtained by two-stage pilot-scale ED can be used to regenerate saturated NDMP-3 anion exchange resins; the regeneration–readsorption performance of NDMP-3 resins was equivalent to that of fresh ≈ 15% w/w NaCl solution. The two-stage dilute solution with low-salt content (0.49% w/w) was further concentrated by pilot-scale UF, so that the HS content in the retentate solution was >30 g/L, which meets the HS content required for water-soluble organic fertilizers. The HS liquid fertilizer could significantly stimulate the growth of green vegetables with no phytotoxicity, mainly due to special properties of HSs. These results demonstrate that ED + UF hybrid technologies can be a promising approach for the sustainable treatment and resource recovery of AIX spent brine.

Effect of TOC Concentration of Humic Substances as an Electron Shuttle on Redox Functional Groups Stimulating Microbial Cr(VI) Reduction.

Humic substances as an electron shuttle play an essential role in the biogeochemistry processes. However, the influence of total organic carbon (TOC) concentrations of humic substances on microbial Cr(VI) reduction remains unclear. In this study, the rates and extents of Cr(VI) reduction by Shewanella oneidensis MR-1 in the presence of Leonardite humic acids (LHA) and Pahokee peat humic acids (PPHA) with different TOC concentrations were evaluated. We found that the enhanced reduction in Cr(VI) was associated with TOC concentrations of 2.5–50 mg C/L of HA samples. The result shows that HA as an electron shuttle impacted both rates and extents of microbial Cr (VI) reduction, which delivered differently in terms of low TOC concentration range of 2.5 to 15 mg C/L and high concentration range of 15–50 mg C/L. The rates of Cr(VI) reduction significantly enhanced in the low TOC concentration range of HA compared to a high concentration range. The highest acceleration rate of Cr(VI) reduction was achieved at 15 mg C/L of HA. The quinone-like fluorophore was responsible for the main redox-active functional groups of HA by the three-dimensional excitation-emission spectroscopy. The fluorescence intensity of quinone-like fluorophore of HA in the low TOC concentration range was positively correlated with its acceleration coefficient, corresponding to the highest microbial Cr(VI) reduction rate obtained in 15 mg C/L of HA. These findings highlighted the effect of the TOC concentration of HA on microbial Cr(VI) reduction processes. It emphasized that the low TOC concentration of HA contributed to the high rates of Cr(VI) reduction, which is critical for better understanding the fate of Cr(VI) and evaluating the effectiveness of Cr(VI) restoration strategies in the future.

Characterization of humic substances isolated from a tropical zone and their role in membrane fouling

Humic substances (HS) are heterogeneous organic polymers that show monotonous properties. HS are present at different proportions in the terrestrial environment, and they implicate the performance of water desalination plants. Recently electrodialysis self-reversal (EDR) technology has been used to treat excess salinity, hardness and fluoride in HS rich groundwater in Sri Lanka (~3 mg L−1, dissolved C). Due to the high organic content of HS in groundwater, the EDR ion exchange membranes are prone to fouling. To unravel the fouling mechanisms, humic acid (HA) and fulvic acid (FA) fractions were isolated and fractionated from the groundwater and characterized spectroscopically. All membrane fouling experiments were conducted for HA and FA contaminated water using a lab-scale EDR setup operated under batch mode. Sequential desorption experiments were carried out using distilled water, 2% (w/w) NaCl, and 0.3% (w/w) sodium dodecyl sulfate to probe variations among two fouling mechanisms. Similarities were found in aromatic and aliphatic carbon contents, humification degree, and molecular weight of humic substances. Higher proportions of carboxylic and phenolic groups were found in FA compared to HA. Ester groups in HA facilitate P, S, and Si migration within organic moieties. The molecular environs in the vicinity of carboxyl functional groups led different fouling mechanisms. HA fouling was found irreversible compared to FA fouling. The subtle differences between fouling mechanisms will help implement appropriate pretreatments to ensure the durability of EDR membranes.

Enriched autoinducer-2 (AI-2)-based quorum quenching consortium in a ceramic anaerobic membrane bioreactor (AnMBR) for biofouling retardation

This study is the first to enrich a facultative QQ consortium for AI-2-based quorum sensing (QS) disruption (FQQ2) and discover its quorum quenching (QQ) performance in an anaerobic membrane bioreactor (AnMBR) for membrane fouling retardation. Herein, FQQ2 was enriched by the enrichment culture using 4,5-dihydroxy-2,3-pentanedione (DPD) followed by anaerobic screening. FQQ2 was composed of various facultative AI-2-based QQ microorganisms including Acinetobacter, Comamonas, Stenotrophomonas, and FQQ2 was capable to degrade 96.96% of DPD in 9 h. More importantly, FQQ2 prolonged membrane filtration operation by an average of 3.72 times via reduction of DPD in the AnMBR treating domestic wastewater (p ≤ 0.05). QQ was implicated to reduce the content of proteins and carbohydrates of the extracellular polymeric substances (EPS) of suspended biomass by 24.16% and 10.39%, respectively, and concentration of proteins of the soluble microbial products (SMP) by 18.77%. Parallel factor (PARAFAC) modelling of excitation-emission matrix (EEM) demonstrated that QQ could reduce the content of fulvic acid-like and humic acid-like substances, aromatic proteins and soluble-microbial-by-product-like proteins of the EPS (p ≤ 0.05) and abate the content of soluble-microbial-by-product-like proteins in the SMP (p ≤ 0.05). The lower EPS content of suspended biomass could be rendered with the reduced relative abundance of AI-2-regulated Christensenellaceae;g-, Hyphomicrobium, Leucobacter and Microbacterium by 48.48%, 76.56%, 64.78% and 59.26%, respectively, and QQ led to the reduction of the relative abundance of Christensenellaceae;g- and Leucobacter in the cake layer by 31.07% and 51.43%, respectively. Moreover, quantity of organics as well as planktonic microorganisms in the supernatant decreased in presence of FQQ2 (p ≤ 0.05). Of note, markedly lower relative abundance of AI-2-regulated Sulfurovum in supernatant by 97.74% resulted in its lower abundance of cake layer. Intriguingly, in the presence of QQ, methane production was statistically enhanced by 62.5% (p ≤ 0.05). It was closely linked to the decrease of sulfate reduction (p ≤ 0.05), which resulted from 37.93% lower abundance of sulfate-reduction Desulfomonile in the suspended biomass (p ≤ 0.05). Collectively, this study sheds lights on the development of AI-2-based QQ for biofouling control in AnMBRs.

Role of biological granular activated carbon in contaminant removal and ultrafiltration membrane performance in a full-scale system

This study evaluated a long-term impact of biological activated carbon (BAC) filter that was employed in a full-scale drinking water treatment plant to enhance the removal of contaminants by the ultrafiltration (UF) process. The results showed that BAC enhanced UF performance by increasing the flux by 18.5% and extending the filtration run by 45%. The presence of BAC improved the removal of primary contaminants, including dissolved organic carbon (4–40%), UV 254 (10–57.7%), geosmin and 2-methylisoborneol (80%). BAC was also effective in decreasing the concentration of biopolymers, humic substances, (semi-)volatile organics, chlorite and halonitromethanes, thereby lowering contaminant load on the UF unit. The changes in primary water quality parameters in the combined process showed that the humic substances in dissolved organic nitrogen, low molecular weight substances in UV 254 , and fluorescence protein-like substances could be useful indicators for DBPs as these organic fractions had strong correlation with DBPs. Obvious spatio-temporal characteristics of GAC grain and microbial communities in BAC filter were observed with operation time and filter depth. The bacterial community in BAC filter was highly diverse and was less influenced by influent quality with an increase in filter depth, while the communities in UF cake layer correlated with organic removal in the UF system. • The BAC performance in a hybrid full-scale DWTP in combination with UF was studied. • BAC could increase the UF flux by 18.5% and extend the filtration run by 45%. • BAC removed 4–40% of DOC, 10–57.7% of UV 254 and 80% of 2- MIB in sand filtrate. • BAC was more effective in controlling N-DBPFP than C-DBPFP, in particular for HNMs. • The microbial communities in BAC filter exhibited temporal and spatial variability.

Seawater browning alters community composition and reduces nutritional quality of plankton in a subarctic marine ecosystem

Inflows of coloured terrestrial organic matter cause seawater browning and reduced phytoplankton production in subarctic coastal ecosystems, potentially deteriorating the nutritional quality of marine food webs. We analyzed the fatty-acid (FA) compositions of seston and the zooplankton taxa Eurytemora affinis and cladocerans at three locations of the northern Baltic Sea. At the coastal and northerly locations, salinity and phosphorus concentrations were low, while concentrations of humic substances (i.e., terrestrial organic matter) were high. The southerly location showed the opposite trend. The ratio between alga-specific ω3 polyunsaturated FA and terrigenous monounsaturated FA (MUFA) in Eurytemora decreased from south to north, as did the ratio between the alga-specific docosahexaenoic acid (DHA) and terrigenous MUFA in cladocerans. With increasing humic substances, the biomass of DHA-rich phytoplankton decreased and the zooplankton MUFA content increased. Our results indicate that coloured terrestrial organic matter alters the phytoplankton composition, consequently affecting the zooplankton nutritional quality.