Microbial Byproduct-like Materials Research Articles

Understanding molecular-level reactions between permanganate/ferrate and dissolved effluent organic matter from municipal secondary effluent

Permanganate (Mn(VII)) and ferrate ((Fe(VI)) oxidations are well-recognized as advanced treatment processes to degrade organic components detected in secondary effluents from municipal wastewater treatment plant (WWTP). However, Mn(VII) or Fe(VI) reactions are sensitive to the water matrix components, especially the dissolved effluent organic matter (EfOM) contained in secondary effluent. Here, we found that Mn(VII) or Fe(VI) hardly mineralize EfOM, but do change its molecular-level composition. Tests with representative trace organic contaminants (TrOCs) spiked to EfOM-rich wastewater effluent showed that Mn(VII) and Fe(VI) preferentially oxidize phenolic TrOCs. UV–vis and fluorescence spectroscopy analyses suggested that molecular properties associated with optical characteristics of reaction solutions are altered by treatment, including decreases in aromaticity, molecular weight, and electron-donating capacity of EfOM. At the molecular-level, the observed phenomenon is ascribed to preferential oxidation of aromatic structures and electron-rich functional groups (e.g., phenolic structures and hydroxyl groups) within EfOM, as well as the transformation and decomposition of macromolecular sulfur- and nitrogen-containing compounds (most likely proteins or microbial byproduct-like material). These findings advance the application of Mn(VII) and Fe(VI) for optimization and proper control of EfOM of emerging concern within treatment trains being developed for advanced treatment facilities.

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.

Algal Organic Matter Drives Methanogen-Mediated Methylmercury Production in Water from Eutrophic Shallow Lakes.

Algal blooms bring massive amounts of algal organic matter (AOM) into eutrophic lakes, which influences microbial methylmercury (MeHg) production. However, because of the complexity of AOM and its dynamic changes during algal decomposition, the relationship between AOM and microbial Hg methylators remains poorly understood, which hinders predicting MeHg production and its bioaccumulation in eutrophic shallow lakes. To address that, we explored the impacts of AOM on microbial Hg methylators and MeHg production by characterizing dissolved organic matter with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy and quantifying the microbial Hg methylation gene hgcA. We first reveal that the predominance of methanogens, facilitated by eutrophication-induced carbon input, could drive MeHg production in lake water. Specifically, bioavailable components of AOM (i.e., CHONs such as aromatic proteins and soluble microbial byproduct-like materials) increased the abundances (Archaea-hgcA gene: 438-2240% higher) and activities (net CH4 production: 16.0-44.4% higher) of Archaea (e.g., methanogens). These in turn led to enhanced dissolved MeHg levels (24.3-15,918% higher) for three major eutrophic shallow lakes in China. Nevertheless, our model results indicate that AOM-facilitated MeHg production could be offset by AOM-induced MeHg biodilution under eutrophication. Our study would help reduce uncertainties in predicting MeHg production, providing a basis for mitigating the MeHg risk in eutrophic lakes.

Insight to peroxone-Fe(III) joint conditioning-horizontal electro-dewatering process on water reduction in activated sludge: Performance and mechanisms

Peroxone disintegration–Fe(III) coagulation (peroxone–Fe(III)) joint conditioning was proposed to enhance the horizontal electro-dewatering (HED) effect of activated sludge (AS). Operating parameters were optimized and the evolutions of AS physicochemical properties, water fractions distribution, organic matter, extracellular polymeric substance (EPS) key components, functional groups, and protein secondary structures during the process were identified. Under the optimized joint conditioning parameters, dewatered AS achieved a final water content of 84.88 ± 0.17% and its bound water content (BWC) was decreased by 1.88 ± 0.28 g/g dry solid. During peroxone pretreatment, the yielded HO decreased the AS floc size, disintegrated the EPS network structure and cell wall, released the bound water, and extracted proteins, polysaccharides, and humic acid-like materials. Furthermore, soluble microbial byproduct-like materials (SMBP) in the EPS layers and tyrosine in tightly bound EPS significantly increased. Protein structures were destroyed, decreasing their water affinity. Subsequent Fe(III) addition re-coagulated broken flocs fragments and EPS fractions, built water flow channels, removed tyrosine and SMBP, and reduced α-helix percentage in slime, facilitating AS dewatering. After joint conditioning, the bound water and intracellular substances were further released by HED. Therefore, the peroxone–Fe(III)–HED process exhibited an excellent performance in AS water reduction.

The conversion of organic nitrogen by functional bacteria determines the end-result of ammonia in compost

The conversion of organic nitrogen determines the quality of composting and its environmental impact, but its underlying microbial mechanism is unclear. Hence, in static composting reactors with forced ventilation, vegetable waste, straw and pig manure were used as raw materials to simulate the composting for 33 days with or without adding 9% biochar. In composting, amino acid and amino sugar nitrogen were most easily converted to ammonium and hydrolysable unknown nitrogen was synthesized from ammonium. The aprA and chiA-related bacteria converted amino acid nitrogen to ammonium, and ammonium to hydrolysable unknown nitrogen, while amoA and HAO-related bacteria converted amine and amino sugar nitrogen to ammonium. Additionally, soluble microbial byproduct-like materials (62.4%) significantly affect organic nitrogen transformation, and could reduce ammonia emission by increasing ammoxidation rates. Thus, whether or not adsorbent substances are added, microorganisms affect the production of ammonia by controlling the conversion of organic nitrogen.

Correlation between oxidation-reduction potential values and sludge dewaterability during pre-oxidation

Pre-oxidation is effective in enhancing sludge dewaterability. Different types and doses of oxidants are used to improve sludge dewaterability in pre-oxidation. Rapid evaluation of the sludge dewaterability is vital for optimizing the type and dose of oxidants in pre-oxidation. It normally takes more time to evaluate sludge dewaterability by measuring typical indicators such as specific resistance to filtration (SRF), content of bound water, and composition of EPS. This study presented a rapid parameter, oxidation-reduction potential (ORP), to correlate it with the dewaterability of pre-oxidized sludge samples. An index of ΔORP (ΔORP = ORPt=0.5 min–ORPt=0 min) showed positive correlations with SRF (r = 0.89, p < 0.05), content of total organic carbon in soluble and loosely-bound EPS (r = 0.86 and 0.84, p < 0.05), zeta potential (r = 0.86, p < 0.05), and content of Fe(III) in the sludge cake (r = 0.92, p < 0.01). However, the ΔORP index showed negative correlations with tryptophan-like proteins, tyrosine-like proteins, microbial byproduct-like materials in tightly-bound EPS (r = −0.85, −0.90 and −0.90, p < 0.05), and sludge particle sizes (p < 0.01). A multiple linear regression model was developed to further reflect the linear correlation between the ΔORP values and the key factors reflecting sludge dewaterability. An optimal dose of oxone (0.4 mmol/g VS) for sludge pre-oxidation with the ΔORP value of 387 mV combined with Fe(III) coagulation conditioning system were verified by the results of dewatering experiments using a laboratory-scale diaphragm filter press. This study demonstrated the feasibility of using ΔORP as a potential rapid evaluation tool for sludge dewaterability.

Relationship between heavy metals and dissolved organic matter released from sediment by bioturbation/bioirrigation

Organic matter (OM) is an important component of sediment. Bioturbation/bioirrigation can remobilize OM and heavy metals that were previously buried in the sediment. The remobilization of buried organic matter, thallium (Tl), cadmium (Cd), copper (Cu) and zinc (Zn) from sediment was studied in a laboratory experiment with three organisms: tubificid, chironomid larvae and loach. Results showed that bioturbation/bioirrigation promoted the release of dissolved organic matter (DOM) and dissolved Tl, Cd, Cu and Zn, but only dissolved Zn concentrations decreased with exposure time in overlying water. The presence of organisms altered the compositions of DOM released from sediment, considerably increasing the percentage of fulvic acid-like materials (FA) and humic acid-like materials (HA). In addition, bioturbation/bioirrigation accelerated the growth and reproduction of bacteria to enhance the proportion of soluble microbial byproduct-like materials (SMP). The DOM was divided into five regions in the three-dimensional excitation emission matrix (3D-EEM), and each part had different correlation with the dissolved heavy metal concentrations. Dissolved Cu had the best correlation with each of the DOM compositions, indicating that Cu in the sediment was in the organic-bound form. Furthermore, the organism type and heavy metal characteristics both played a role in influencing the remobilization of heavy metal.

Using a tubular photosynthetic microbial fuel cell to treat anaerobically digested effluent from kitchen waste: Mechanisms of organics and ammonium removal

Anaerobically digested effluent from kitchen waste (ADE-KW) was used herein as the substrate of a tubular photosynthetic microbial fuel cell (PMFC) for power production, and also, after being diluted, as a medium for cultivation of algae in the cathodic chamber. Adding 3 mg/L phosphorus to the catholyte could efficiently enhance the algal growth and the PMFC performance. About 0.94 g/L algal biomass and 0.57 kWh/m3-ADE-KW bioelectricity were obtained from the PMFC. Soluble microbial byproduct-like material and aromatic proteins were the dominant organics in the ADE-KW, which were readily degradable in the system. About 79% of the 1550 mg/L ammonium in the anolyte transferred to the catholyte through the cation exchange membrane. The ammonium was removed mainly as electron acceptors at the cathode after being oxidized by oxygen, whereas algal assimilation only account for about 14.6% of the overall nitrogen.

Impact of spring flooding on DOM characterization in a small watershed of the Hun River, China

Potential water pollution derived from melting snow is a growing concern to watershed management in northern climates. For most small watersheds in the Hun River Basin, substantial portions of the annual load of pollutants such as organic matter, ammonia, phosphorus and metals come from snowmelt and early spring runoff. Thus, the annual spring flood is a real threat to the trophic state and water quality of Hun River. By three-dimensional fluorescence technology, the composition and characteristics of dissolved organic matter (DOM) in early spring runoff of a small watershed (the Baitapu River) were analyzed, and the correlation with land use was investigated. The result showed that compared with NH3-N and TP, DOM was not the major contributor to water quality deterioration in spring flooding, but its composition still presented significant differences. Compared with that in medium flow period, the abundance of a soluble microbial byproduct-like material in the spring-flood period decreased from 28.6 to 15.8 %, while those of tyrosine-like material and humic-like material increased from 36.0 and 1.8 % to 44.4 and 10.7 %, respectively. DOM in spring flooding had a relatively higher aromaticity degree, a greater humification level, and a larger molecular weight. Meanwhile, DOM from urban areas contained more tyrosine-like material. For the Baitapu River, urban areas were the major DOM source in both the medium flow period (from dispersed point sources) and the spring flood period (from a wastewater treatment plant). Therefore, DOM composition can be used as an effective indicator for tracking pollution sources.

Identification of the function of extracellular polymeric substances (EPS) in denitrifying phosphorus removal sludge in the presence of copper ion

Industrial wastewater containing heavy metals that enters municipal wastewater treatment plants inevitably has a toxic impact on biological treatment processes. In this study, the impact of Cu(II) (0, 1.5, 2, 2.5, 3 mg/L) on the performance of denitrifying phosphorus removal (DPR) and microbial community structures was investigated. Particularly, the dynamic change in the amount and composition of extracellular polymeric substances (EPS), and the role of EPS in P removal, were assessed using three-dimensional excitation–emission matrix fluorescence spectroscopy combined with parallel factor (PARAFAC) analysis. The results showed that, after long-term adjustment, the P removal efficiency was maintained at 95 ± 2.7% at Cu(II) addition up to 2.5 mg/L, but deteriorated when the Cu(II) addition was 3 mg/L. The EPS content, including proteins and humic substances, increased with increasing Cu(II) additions at concentrations ≤2.5 mg/L. This property of EPS was beneficial for protecting phosphate-accumulating organisms (PAOs) against heavy metals, as both proteins and humic substances are strong ligands for Cu(II). Therefore, the PAOs abundance was still relatively high (67 ± 3%) when Cu(II) accumulation in sludge was up to 10 mg/g SS. PARAFAC confirmed that aromatic proteins could be transformed into soluble microbial byproduct-like material when microorganisms were subjected to Cu(II) stress, owing to their strong metal ion complexing capacity. The increase in the percentage of humic-like substances enhanced the detoxification function of the sludge EPS. EPS accounted for approximately 26–47% of P removed by adsorption when Cu(II) additions were between 0 and 2.5 mg/L. The EPS function, including binding toxic heavy metals and P storage, enhanced the operating stability of DPR systems. This study provides us with a better understanding of (1) the tolerance of DPR sludge to copper toxicity and (2) the function of sludge EPS in the presence of heavy metals in biological P removal systems.

Composition, source characteristic and indication of eutrophication of dissolved organic matter in the sediments of Erhai Lake

Composition and source characteristics of dissolved organic matter (DOM) in the surface sediments of Erhai Lake were studied by using fluorescence spectroscopy and UV–Vis absorbance. Moreover, the influence factors and the indication significance for eutrophication are also discussed. The results are as follows: (1) The DOC content of Erhai Lake sediments ranges from 0.17 to 0.77 g kg−1, which is higher in dry season than that in wet season. Its DOC content of the sediment from the northern part is higher than that from the southern, and that is the smallest in the central. Moreover, DOM in Erhai Lake sediments comprise of protein- and humic-like substances. The average contents of protein-, fulvic acid-like substances and soluble microbial byproduct-like materials in the wet season are higher than those in the dry season by 25.92, 11.82 and 2.96 %, respectively; while the content of humic-like substance in the wet season is lower than that in the dry season by 6.94 %. As to the spatial distribution, the contents of protein- and fulvic acid-like substances are the highest in the central of Erhai Lake sediments, and that of the humic-like substance is the highest in the southern part. In addition, the humification degree of DOM in the dry season is higher than that in the wet season. (2) The DOM in Erhai Lake sediments mainly originated from terrestrial sources, of which the terrestrial pollutant has a main impact in the dry season, and the terrestrial pollutant input and biogenetic derivation play an equally important part in the wet season. Terrestrial pollutant and aquatic plants are the important factors that influence the DOM composition of Erhai Lake sediments. (3) The characteristic parameter (P(III+V,n)/P(I+II,n)) (the content ratio of humic-like substance to protein-like substances) of the DOM composition of Erhai Lake sediments is positively correlated with the contents of the different nitrogen (N) forms in the sediments (R2 = 0.68–0.83, P < 0.01). The contents of N forms in sediments and its source characteristic can be reflected by the P(III+V,n)/P(I+II,n) value. So the P(III+V,n)/P(I+II,n) value can be taken as the indirect indicator of the contents of N forms in sediments. Moreover, the composition characteristic of DOM in sediments can reflect the contents of N forms to some extent, that is, the risk of N release from Erhai Lake sediments can be indicated to some extent.

Advanced treatment of effluent from municipal WWTP with different metal salt coagulants: Contaminants treatability and floc properties

Chemical coagulation with three representative inorganic coagulants was used for the advanced treatment of secondary effluent from WWTP to enhance total phosphorus (TP) and organic removal. The effect of chemical coagulation on organic contaminants was investigated with combined fluorescence excitation–emission matrix (EEM) spectroscopy and High-performance size-exclusion chromatography (HPSEC). The results showed that different coagulation features and benefits were exhibited by FeCl3, Al2(SO4)3 and polyaluminum chloride (PACl). PACl had better performance in chemical oxygen demand (COD) removal, while FeCl3 and Al2(SO4)3 were more efficient in removing TP. The optimal coagulant in this study was FeCl3. The floc obtained from FeCl3 coagulation was larger, easier to settle and break than that of Al2(SO4)3 and PACl. Coagulation mainly removed orthophosphate and the major phosphorus fraction of coagulated effluent was organic phosphorus. The macromolecule organics (molecular weight (MW)>10kDa) were completely removed regardless of their chemical nature, while inorganic coagulants showed different effects on removal efficiency of organic matters with a MW less than 10kDa. Besides, 71.24% of the total dissolved organic carbon (DOC) was tryptophan-like proteins and soluble microbial byproduct-like materials which could easily be removed by coagulation.

Functional diversity changes of microbial communities along a soil aquifer for reclaimed water recharge

The physiochemical and functional diversity of soil-attached microorganisms was investigated using a stabilized laboratory-scale soil aquifer treatment (SAT) system. In this system, reclaimed water after ozonation was used as the feed water, and 60% dissolved organic carbon was removed by the unsaturated vadose layer in 0.8days. Soil biomass (volatile solids, phospholipid extraction) and functional diversity significantly decreased from the unsaturated vadose layer to the saturated aquifer, where they maintained the same level. Using principal components analysis based on substrate utilization pattern, the vadose layer soil sample was clearly separated from the saturated layer samples. Exceptionally, the oxidation rates of esters remained stable during SAT, indicating the purification potential on certain recalcitrant organic compounds in the saturated aquifer given an adequate retention time. Correlation analysis revealed that organic carbon was the key limiting factor for microbial biomass and activity, especially for tyrosine-like aromatic proteins and soluble microbial byproduct-like materials.

Effect of Composting on Dissolved Organic Matter in Animal Manure and Its Binding with Cu

The agricultural application of raw animal manure introduces large amounts of dissolved organic matter (DOM) into soil and would increase transport of heavy metals such as Cu which are widely present in animal manure. The purpose of this research was to evaluate the evolution of DOM from pig and cattle manures during composting through excitation-emission matrix (EEM) fluorescence spectroscopy and the binding ability of DOM toward copper (Cu) ions with the aid of fluorescence quenching titration. The excitation-emission matrix spectra indicated that tyrosine-like, tryptophan-like, and soluble microbial byproduct-like fluorescence decreased significantly, while humic-like and fulvic-like fluorescence increased and became the main peaks in composted manure DOM. Fluorescence quenching titration showed that the complexing capacities of pig and cattle manure DOM decreased after composting. Correlation analysis confirmed that complexing capacity of DOM positively and significantly correlates with tyrosine-like and soluble microbial byproduct-like materials which mostly degraded after composting. These results would suggest that the ability of manure DOM to complex with Cu is inhibited as a result of reduced protein-like materials after composting.

Characterizing membrane foulants in MBR with addition of polyferric chloride to enhance phosphorus removal

The effect of polymeric ferric chloride (PFC) addition on phosphorus removal and membrane fouling were investigated in an anoxic/oxic submerged membrane bioreactor. The total phosphorus concentration in effluent averaged at 0.26mg/L with PFC addition of 10–15mg/L, while the rate of membrane fouling increased 1.6 times over the control MBR (without PFC addition). Three-dimensional excitation–emission matrix fluorescence spectroscopy and Gel Filtration Chromatography analysis indicated that soluble microbial byproduct-like materials and large molecules (MW>100kDa) were one of the main contributors of biofouling. Fourier transform infrared spectrum confirmed that the major components of the cake layer were proteins and polysaccharides materials. Scanning electron microscopy demonstrated that membrane surfaces were covered with compact gel layer formed by organic substances and Energy Dispersive X-ray analysis indicated that ferric metals were the most important inorganic pollutants. Consequently, soluble organic substances and dose of PFC should be controlled to minimize membrane fouling.

Extracellular biological organic matters in microbial fuel cell using sewage sludge as fuel

The microbial fuel cell (MFC) was applied to produce electricity using sewage sludge as a fuel. The extracellular biological organic matter (EBOM) of sludge, before and after MFC operation, was extracted using ammonium hydroxide whose hydrophobicity was characterized with XAD resin fractionation technique. Following MFC operation, the hydrophilic fraction (HPI) of EBOM was enriched (48.0%–64.5%), the hydrophobic acid (HPO-A) fraction was reduced (32.0%–14.5%), and the dissolved organic carbon (DOC) was removed by 36.8% and the sludge aromaticity decreased by 65.7%. The fluorescence tests indicated that the MFC removed the aromatic proteins-like and soluble microbial byproduct-like materials in sludge. Fourier-transform infrared (FT-IR) results showed that the aliphatic (C–H related) components, hydrocarbon and carbohydrate were easily hydrolyzed and biodegraded in the studied MFC.

Characterizing the release of different composition of dissolved organic matter in soil under acid rain leaching using three-dimensional excitation–emission matrix spectroscopy

Although excitation–emission matrix spectroscopy (EEMS) has been widely used to characterize dissolved organic matter (DOM), there has no report that EEMS has been used to study the effects of acid rain on DOM and its composition in soil. In this work, we employed three-dimensional EEMS to characterize the compositions of DOM leached by simulated acid rain from red soil. The red soil was subjected to leaching of simulated acid rain of different acidity, and the leached DOM presented five main peaks in its EEMS: peak-A, related to humic acid-like (HA-like) material, at Ex/Em of 310–330/395–420 nm; peak-B, related to UV fulvic acid-like (FA-like) material, at Ex/Em of 230–280/400–435 nm; peak-C and peak-D, both related to microbial byproduct-like material, at Ex/Em of 250–280/335–355 nm and 260–280/290–320 nm, respectively; and peak-E, related to simple aromatic proteins, at Ex/Em of 210–240/290–340 nm. EEMS analysis results indicated that most DOM could be lost from red soil in the early phase of acid rain leaching. In addition to the effects of the pH of acid rain, the loss of DOM also depended on the properties of its compositions and the solubility of their complexes with aluminum. HA-like and microbial byproduct-like materials could be more easily released from red soil by acid rain at both higher pH (4.5 and 5.6) and lower pH (2.5 and 3) than that at middle pH (3.5). On the contrary, FA-like material lost in a similar manner under the action of different acid rains with pH ranging from 2.5 to 5.6.