Municipal Secondary Effluent Research Articles

Degradation of emerging pharmaceutical micropollutants in municipal secondary effluents by low-pressure UVC-activated HSO5− and S2O82− AOPs

Abstract The degradation of six representative emerging pharmaceuticals (PhACs) (carbamazepine (CBZ), crotamiton (CRMT), N,N-diethyl-meta-toluamide (DEET), gemfibrozil (GEM), ibuprofen (IBP) and trimethoprim (TMP)) mixture in municipal secondary effluents by UVC-activated HSO5− and S2O82− were investigated and compared to UV/H2O2 process. The results showed that the PhACs degradation efficiencies by UV/HSO5− were typically smaller than those obtained by UV/H2O2. In contrast, UV/S2O82− offered larger degradation efficiencies of CBZ, GEM, IBP and TMP in comparison to UV/H2O2, which however was less effective in degrading CRMT and DEET. The electron spin resonance (ESR) and radical scavenging tests indicated that hydroxyl radical (HO•) was the major reactive species responsible for the degradation of PhACs by UV/HSO5−, while both sulfate radical (SO4•−) and HO• contributed to PhACs degradation by UV/S2O82−. The rate constants of PhACs reacting with HO•/SO4•− were determined on the basis of their degradation kinetics. All PhACs have large rate constants with HO• over the range of (7.66–9.86) × 109 M−1 s−1. Among of them, CBZ, GEM, IBP and TMP have large rate constants with SO4•− at (1.48–4.59) × 109 M−1 s−1. However, CRMT and DEET have smaller rate constants with SO4•− at 2.84 × 108 and 2.95 × 108 M−1 s−1, respectively, thereby resulting in limited degradation efficiencies by UV/S2O82−. The degradation intermediates of PhACs were investigated and tracked by LC-QTOF-MS. Evolution of effluent organic matters (EfOM) was investigated by means of excitation-emission fluorescence matrices (EEFM), indicating successful destruction of EfOM by HO•/SO4•−. The reaction stoichiometric efficiencies (RSE) of Δdissolved organic carbon (DOC)/Δoxidants were compared, suggesting high oxidant utilization efficiencies for UV/HSO5− and UV/S2O82− at 66.8% and 52.0%, respectively.

Removal of a mixture of pharmaceuticals sulfamethoxazole and diclofenac from water streams by a polyamide nanofiltration membrane.

Wastewater treatment plants are not specially designed to remove pharmaceutically active compounds (PhACs), since these substances are toxic and bio-refractory. This paper aims to investigate and optimize the performance of the Trisep TS80 nanofiltration (NF) membrane for the removal of a mixture of two of the most detected PhACs in municipal wastewaters worldwide, sulfamethoxazole and diclofenac. Several NF tests were carried out to study the rejections of these contaminants both spiked in demineralized water, filtrated water taken from Mondego River and secondary effluent coming from a municipal wastewater treatment plant. Among the several studied operating variables, pH was the one that most affected the contaminant rejection and membrane permeability. In the case of synthetic effluent, an applied pressure of 10 bar and pH 7 were determined as the best operating conditions, which allowed almost total chemical oxygen demand retention and a global contaminant rejection of 96.3% to be achieved. The application of different water matrices (river water and secondary municipal effluent) had no relevant impact on process efficiency. Vibrio fischeri luminescence inhibition tests revealed that treatment by nanofiltration reduced acute toxicity of all studied effluents.

Combined heterotrophic and autotrophic system for advanced denitrification of municipal secondary effluent in full-scale plant and bacterial community analysis

Total nitrogen (TN) removal is the major technical challenge for wastewater treatment plants to meet the more stringent discharge standard. In this study, lab- (0.05 m3/d), pilot- (1000 m3/d) and full-scale (10,000 m3/d) combined heterotrophic and autotrophic denitrification reactors (HARs) were designed and operated to treat municipal secondary effluent. During the 110-day stable operation, the effluent TN was reduced below 2.5 mg/L without secondary pollution causing by the excessive addition of organics, close to Class IV of Environmental Quality Standards for Surface Water. The bacterial richness and diversity increased with the expansion of reactor scale. Denitrifying bacteria (DB) dominated in all reactors, however, Thiomonas (12.42%), Methylotenera (6.35%), Thiobacillus (20.62%), Methyloverstatilis (5.44%) and Thauera (8.21%) were the main genera in lab-, pilot- and full-scale reactors respectively. The denitrification efficiency temporarily deteriorated at the later stage, and redundancy analysis (RDA) indicated the obviously increased sulfate reducing bacteria (SRB) and sulfide were main contributors. Sludge supplement rapidly recovered the reactors performance in five days. This study suggests that HARs could be a promising technique for advanced denitrification of the municipal secondary effluent.

Environmentally friendly approach for advanced treatment of municipal secondary effluent by integration of micro-nano bubbles and photocatalysis

Abstract Numerous organic contaminants existing in the municipal secondary effluent (SE) have gained considerable attention because of their persistent nature and adverse environmental effects. In this study, micro-nano bubbles (MNB) and UV/Titanium dioxide (TiO2) system, both individual and in combination, were investigated for advanced treatment of the SE. The integrated MNB and photocatalysis system significantly improved the removal of chemical oxygen demand (COD) and persistent organic pollutants by 27.52 and 14.38%, respectively. The hybrid system efficiently decreased all five categories of organic contaminants according to excitation-emission matrix (EEM) spectrum, while the molecular weight (MW) fractions were decreased and the UV-absorbance at wavelength 254 nm (UV254) of MW (

Ni-Fe layered double hydroxides catalized ozonation of synthetic wastewater containing Bisphenol A and municipal secondary effluent

Ni-Fe Layered Double Hydroxides (Ni-Fe LDHs) was prepared, characterized and used as catalyst in heterogeneous catalytic ozonation of Bisphenol A (BPA) and other organic compounds in secondary effluent. The characterization and ozonation results revealed that the Ni-Fe LDHs possessing a Ni: Fe ratio of 3:1 had the best crystalline and the highest affinity for ozone. Under the optimized conditions, the final TOC and COD removal achieved was 56% and 68%, respectively. BPA in the secondary effluent could be removed completely by Ni3-Fe LDH catalyzed ozonation. The organic compounds removal was mainly attributed to the oxidation by free active radicals such as hydroxyl radicals (OH). In this research the accumulative ·OH in the reaction system was determined to be 28.2 μmol at the reaction time of 60 min. The free active radicals were mostly generated through the electron transfer among different valences of metals on Ni-Fe LDHs surface, and subsequently diffused into bulk solution to oxidize the target organic compounds there.

Intensifying ozonation treatment of municipal secondary effluent using a combination of microbubbles and ultraviolet irradiation.

Ozonation treatment of municipal secondary effluent is complicated by the low solubility of ozone and inefficient production of hydroxyl free radicals from ozone decomposition. To resolve these problems, this study investigated methods for intensifying ozonation treatment, using a combination of microbubbles and ultraviolet (UV) irradiation (UV/MBO). The high efficiency of the method was illustrated by treating river water containing refractory components derived from secondary effluent in a wastewater treatment plant. The results showed that the ozone mass transfer coefficient in a microbubble system was an order of magnitude compared with a conventional macrobubble system at the initial stage. The amount of ·OH generated during the treatment was quantified using a fluorescent probe analysis. The amount of ·OH in the UV/MBO system was almost 2-6 times more than the amount found with conventional ozonation using macrobubbles (CO), CO with UV irradiation (UV/CO), and microbubble ozonation (MBO) units. The UV/MBO system achieved chemical oxygen demand (COD), UV254, and UV400 removal performance rates of up to 37.50%, 81.15%, and 94.74% respectively. These levels were 2-36% higher than those in other systems. The coupling UV/MBO treatment significantly reduced all five categories of substances according to EEM spectra and fluorescence regional integration. The distribution of fractions with different molecular weights (MW) was altered and the UV254 of MW (< 500Da) increased by 15.8%. The biodegradability of the water was significantly improved, as indicated by the TOC/UV254. This is ascribed to the enhanced degradation of refractory organics in the water. The combination of the UV/microbubble technique with ozonation could provide an efficient approach for advanced wastewater treatment. Graphical abstract.

Influence of industrial contamination in municipal secondary effluent disinfection by UV/H2O2.

Advanced oxidation processes, including UV/H2O2, are methods able to remove diverse classes of organic contaminants and disinfect water and wastewater. However, the variation in the matrix composition can influence the inactivation of microorganisms due to the presence of competing reactive material, which consumes the available oxidants. This problem can lead to the use of inadequate oxidant/radiation dose and disturb a correct treatment. The aim of this study was to assess the efficiency of UV/H2O2 to inactivate microbiological indicators in secondary effluents in the presence of high concentration of carbonate, nitrate, metals, and industrial organic contaminants. Metals had a positive influence on inactivation acting as catalysts. Zn, Fe, and all metals simultaneously presented toxic effects to the indicator organisms in the higher concentrations before the treatment. Even in metals presence, the negative effect of carbonate and the industrial organic contaminants on indicators inactivation was very important. Bacteria regrowth after 72h was also affected by the same inhibiting substances, but the metals acted positively inhibiting it. The disinfection indicators had different sensibilities to the spiked substances. Escherichia coli inactivation was more affected than total coliforms by the presence of the industrial contamination, which can lead to different interpretation of inhibition degree depending of the used disinfection indicator.

Simultaneous removal of tetracycline and disinfection by a flow-through electro-peroxone process for reclamation from municipal secondary effluent.

Pharmaceutical and personal care products as one of the micropollutants and bacteria in secondary effluent restrict the water reuse from municipal secondary effluent. Electro-peroxone (EP) process where H2O2 is generated in-situ by electrolysis is an emerging advanced oxidation process and an improvement of traditional peroxone method (O3/H2O2). In this work, a flow-through EP process was compared with ozonation and electrolysis for simultaneous disinfection and degradation of tetracycline (TC). The disinfection effect by EP was higher than the sum of standalone ozone and electrolysis and the coupling coefficient of ozonation and electrolysis in EP process was 1.2. The flow-through EP system presented similar efficiency for separately and simultaneously treating E. coli and TC. For the actual secondary effluent treatment, trihalomethanes, haloacetonitrile and halonitromethanes, the main disinfection by-products, were much lower than the WHO's thresholds for drinking water. TOC and COD removal was 44% and 65%, respectively, at flow rate of 35 mL/min. BOD5, bacteria, pH and other parameters in the effluent could satisfy the recreational landscape water quality standard, and the required energy consumption was 0.47 kW h/m3 at the flow rate 35 mL/min. Most of the degradation products were small-molecule organic acids, and possible degradation pathway of TC was suggested.

Mercury removal from municipal secondary effluent with hydrous ferric oxide reactive filtration

This study evaluated the ability of hydrous ferric oxide reactive filtration (HFO-RF) to remove mercury (Hg) from municipal secondary effluent at four study sites. Pilot HFO-RF systems (136m3 /day) at two sites demonstrated total Hg concentration removal efficiencies of 96% (inflow/outflow mean total Hg: 43.6/1.6 ng/L) and 80% (4.2/0.8 ng/L). A lightly loaded medium-scale HFO-RF system (950m3 /day) had a concentration removal efficiency of 53% (0.98/0.46ng/L) and removed 0.52mg/day of total Hg and 2.2μg/day of methyl-Hg. A full-scale HFO-RF system (11,400m3 /day) yielded a total Hg concentration removal efficiency of 97% (87/2.7ng/L) and removed an estimated 0.36kg/year of Hg. Results suggest that the quality of secondary effluent, including dissolved organic matter content, affects achievable minimum total Hg concentrations in effluent from HFO-RF systems. Low HFO-RF effluent concentrations (<1ng/L) can be expected when treating secondary effluent from suspended-growth biological treatment systems. PRACTITIONER POINTS: Trace levels of mercury in municipal secondary effluent can negatively impact receiving waters. Hydrous ferric oxide reactive filtration (HFO-RF) can remove mercury from municipal secondary effluent to levels below the Great Lakes Initiative discharge standard of 1.3 ng/L. Mercury removal to low concentrations (< 1 ng/L) using HFO-RF appears to be associated with secondary effluents with low dissolved organic matter content. HFO-RF can also remove total phosphorus and turbidity to low concentrations.

Assessment of 4‐Aminoantipyrine Degradation and Mineralization by Photoelectro‐Fenton with a Boron‐Doped Diamond Anode: Optimization, Treatment in Municipal Secondary Effluent, and Toxicity

Abstract4‐Aminoantipyrine (4‐AA), a persistent metabolite of dipyrone found in natural water, has been treated in 100 mL of aqueous 0.050 M Na2SO4 solutions at pH 3.0 by photoelectro‐Fenton (PEF) with a 4 W UVA lamp. The assays were performed in a cell equipped with a boron‐doped diamond (BDD) anode and an air‐diffusion cathode for H2O2 generation. The formation of an unstable Fe(III)‐4‐AA complex with 1 : 2 molar ratio was evidenced. A 24 central composite design was used to assess the effect of four independent variables on PEF performance. The optimized conditions for 62.5 mg L−1 4‐AA were: current density of 77.5 mA cm−2 and 47.75 mg L−1 Fe2+, yielding 99 % 4‐AA degradation at 7 min, and 45 % 4‐AA mineralization with 3.2 % mineralization current efficiency at 130 min. Slightly slower degradation and similar mineralization were obtained under these conditions when 4‐AA was spiked into a municipal secondary effluent, showing a low influence of natural organic matter on PEF. The initially high acute toxicity determined using Artemia salina was largely diminished upon PEF treatment.

Simultaneous sulfadiazines degradation and disinfection from municipal secondary effluent by a flow-through electro-Fenton process with graphene-modified cathode.

Conventionally the deep treatment and disinfection are fulfilled by different processes for municipal wastewater treatment, this work verified a breakthrough by one process of novel flow-through electro-Fenton (EF) with graphene-modified cathode, which is usually seemed to be ineffective. This process was firstly confirmed to be cost-effective for simultaneous sulfadiazines (SDZs) degradation and disinfection from municipal secondary effluent with a very low electrical energy consumption (EEC) of 0.21 kW h/m3, attributed to the high H2O2 production of 4.41 mg/h/cm2 on the novel graphite felt cathode modified by electrochemically exfoliated graphene (EEGr) with a low EEC of 3.08 kW h/(kg H2O2). Compared with the ineffective SDZs degradation by the conventional flow EF, this process was more cost-effective and overcame the harsh requirements on electrolyte concentration. It also showed good effectiveness in the degradation of different antibiotics, and the graphene-modified cathode still kept stable performance after eight consecutive runs. Account for the combined action of OH and active chlorine, the formation of hydroxylated and chlorine containing by-products was confirmed, and a possible degradation mechanism for SDZs was proposed. This flow-through EF process provided an alternative method for the disinfection and antibiotics degradation by one process for the treatment and reuse of municipal secondary effluent.

Detailed modeling and advanced control for chemical disinfection of secondary effluent wastewater by peracetic acid

Advanced control of chemical disinfection processes is becoming increasingly important in view of balancing under-treatment (low pathogen inactivation) and over-treatment (excessive consumption of disinfectant and disinfection byproducts formation) thereby providing considerable environmental and economic benefits. Conventional control strategies such as flow pacing or residual trim ignore chemical demand/decay, inactivation kinetics, and other factors governing disinfection performance in continuous-flow reactors such as reactor hydraulics and process variability. This study presents the development, verification, and pilot-scale validation of a novel CT-based real-time disinfection control strategy, derived from first principles, and applied to peracetic acid disinfection of municipal secondary effluent wastewater. Validation experiments were carried out using a 3-m3 pilot contact basin of which the hydraulic performance was first characterized by means of tracer tests and then mathematically modeled using the well-established theoretical framework of continuous stirred-tank reactors in series. The analytical model describing hydraulic performance was subsequently extended to take into account disinfectant demand/decay and microbial inactivation kinetics. The integrated model was successfully used to predict, and control, residual peracetic acid as well as microbial concentration in the pilot effluent. Validation studies conclusively supported that the novel CT-based control strategy was superior in maintaining constant disinfection performance, desired microbial counts, and low residual disinfectant under variable flow and wastewater quality. When compared with flow pacing, the CT-based control required two times less the amount of chemical for the same treatment objective (<100 cfu/100 mL). Remarkably, the CT-based control strategy could be extended to other chemical disinfection processes such as chlorination and ozonation, alone or in combination with physical treatment technologies such as membranes and ultraviolet irradiation.

Formation of N-nitrosamines during the analysis of municipal secondary biological nutrient removal process effluents by US EPA method 521

US EPA Method 521 employs activated carbon-based solid phase extraction (SPE) cartridges for analyzing N-nitrosamines. The analysis of N-nitrosamines and their chloramine-reactive and ozone-reactive precursors in nitrified municipal secondary effluent revealed the potential for NDMA to form as an artefact during the analysis. As samples passed through the SPE cartridge, the activated carbon mediated the reaction of nitrite with dimethylamine to form NDMA. The reaction was not significant with tertiary amines. Artefactual NDMA formation was important for nitrite concentrations >0.2 mg/L as N in the Biological Nitrogen Removal (BNR) process effluent. However, it is difficult to define a general threshold for nitrite concentrations, because the importance of the reaction also depends on secondary amine concentrations, which are usually poorly characterized. Pre-treatment of samples with sulfamic acid to destroy nitrite mitigated the artefact. This artefact did not affect NDMA analysis in a nitrified effluent from another facility, likely due to low dimethylamine concentrations. This artefact also did not affect the analysis of primary effluent, due to the lack of nitrite, or the analysis of other N-nitrosamines, likely due to the lack of their secondary amine precursors. Because chloramination does not significantly degrade nitrite, this artefact could affect the analysis of chloramine-reactive N-nitrosamine precursors. Because ozonation rapidly degrades nitrite, it should not affect the analysis of ozone-reactive precursors. However, ozonation at 0.8 mg ozone/mg dissolved organic carbon resulted in significant degradation of all N-nitrosamines, even though simultaneous NDMA formation from ozone-reactive precursors resulted in a net increase in NDMA concentration.

Distribution of endocrine-disrupting chemicals in colloidal and soluble phases in municipal secondary effluents and their removal by different advanced treatment processes

In this work, the partition of endocrine-disrupting chemicals (EDCs) in colloid-bound and truly dissolved phases in municipal wastewater before and after advanced treatment processes was determined. The effluents, which were filtered using a 0.45 μm membrane, were further separated with the 1 kDa cross-flow ultrafiltration system into two phases, namely, colloidal phase (0.45 μm-1 kDa) and soluble phase (<1 kDa), and the partition coefficients of typical EDCs to colloids (Kcoc) were calculated. The removal of typical EDCs and their estrogenic activity in secondary effluent by coagulation sedimentation (CS), granular activated carbon (GAC) adsorption, magnetic ion exchange resin (NDMP), and ozone processes was compared. Results show that the percentages of colloid-bound EDCs were noteworthy and ranged between 7.8% and 44.3% in secondary effluents. The reduction in EDCs resulting from the GAC adsorption process was positively correlated to their logKcoc, thus suggesting that the adsorption of EDCs onto granular activated carbon and colloids exhibited a similar phenomenal character. Ozone oxidation was most effective in removing both colloidal phase and soluble phase EDCs, whereas CS displayed a relatively adequate performance in reducing colloidal EDCs. EDCs with lower Kow values exhibited higher removal by ion exchange resin. The combination of modified NDMP and ozonation processes achieved the best performance in reducing estrogenic activity and satisfying the predicted no-effect concentration (PNEC).

Fenton oxidation of municipal secondary effluent: comparison of Fe/Ce-RGO (reduced graphene oxide) and Fe2+ as catalysts

The advanced treatment of municipal secondary effluent by heterogeneous and homogeneous Fenton processes using Fe/Ce-RGO (reduced graphene oxide) and Fe2+ as catalysts was studied and compared. Sulfamethazine (SMT) was spiked in the effluent to examine the effectiveness of the emerging contaminant removal. The Fe/Ce-RGO catalyst was characterized using a scanning electron microscope (SEM) and cycle voltammetry curves. The removal of dissolved organic carbon (DOC), soluble chemical oxygen demand (SCOD), SMT, and ultraviolet-visible spectroscopy in 254nm (UV254) of municipal secondary effluents was examined. The DOC removal efficiency of secondary effluent (without addition of SMT) was 36.30% and 11.74% using Fe/Ce-RGO and Fe2+ as catalysts, respectively. The removal efficiency of DOC, SCOD, and SMT in heterogeneous Fenton process was higher than that in homogeneous Fenton process. The changes of three-dimensional excitation-emission matrix (3DEEM) fluorescence, soluble microbial products (SMPs), humic acids, and UV254 were determined, and the results indicated that UV254, aromatic proteins, and humic acids decreased rapidly in both processes; however, polysaccharides and protein-like substances were difficult to degrade. Although some toxic substances produced after Fenton-like treatment, the biodegradability of the treated effluent was enhanced.

Novel materials for catalytic ozonation of wastewater for disinfection and removal of micropollutants

The purpose of this work was to identify novel materials that could be used for the catalytic ozonation of wastewater for improved removal of micropollutants and disinfection. The materials chosen for investigation were selected based on their commercial availability and composition characteristics that suggested that they could act as catalysts. Synthetic wastewater (SWW) was used to mimic municipal secondary effluent wastewater while obtaining constant and reproducible matrix characteristics. Polonite®, wollastonite, zeolite, TiO2-Al2O3 (8%/92%), and AL-1010S (AlO2-based) were tested for their potential impact on efficiency of disinfection, based on the removal of E. coli bacteria and removal of contaminants of emerging concern (CECs), relative to conventional ozonation. Atrazine (ATZ), ibuprofen (IBP), naproxen (NPX), and gemfibrozil (GBZ) were used as indicator compounds. Zeolite and wollastonite did not promote disinfection and CECs removal; TiO2-Al2O3 and AL-1010S provided improvement for both criteria, but to a lesser extent in SWW than in Milli-Q water; and Polonite® did not enhance the removal of CECs but led to the higher E. coli inactivation. These results suggest that Polonite®, AL-1010S, and TiO2-Al2O3 can act as catalysts and provide mechanisms to lower the ozone dose required to reach disinfection. The apparent kinetic constant of the reaction for the catalytic ozonation of ATZ, in the ultrapure water, was determined for Polonite®, TiO2-Al2O3 and AL-1010S. The reusability of the catalysts was demonstrated over four consecutive cycles of 6 h of treatment in a continuous flow ozonation system.

Impacts of virus processing on human norovirus GI and GII persistence during disinfection of municipal secondary wastewater effluent

Noroviruses cause significant global health burdens and waterborne transmission is a known exposure pathway. Chlorination is the most common method of disinfection for water and wastewater worldwide. The purpose of this study was to investigate the underlying causes for discrepancies in human norovirus (hNoV) resistance to free chlorine that have been previously published, and to assess hNoV GI and GII persistence during disinfection of municipal secondary wastewater (WW) effluent. Our results reveal that choice of hNoV purification methodology prior to seeding the viruses in an experimental water matrix influences disinfection outcomes in treatment studies. Common hNoV purification processes such as solvent extraction and 0.45-μm filtration were ineffective in removing high levels of organics introduced into water or wastewater samples when seeding norovirus positive stool. These methods resulted in experimental water matrices receiving an additional 190 mg/L as Cl2 of 15-s chlorine demand and approximately 440 mg/L as Cl2 of 30-min chlorine demand due to seeding norovirus positive stool at 1% w/v. These high organic loads impact experimental water chemistry and bias estimations of hNoV persistence. Advanced purification of norovirus positive stool using sucrose cushion ultracentrifugation and ultrafiltration reduced 15-s chlorine demands by 99% and TOC by 93% for loose (i.e. unformed diarrhea) stools. Using these methods, hNoV GI and GII persistence was investigated during free chlorination of municipal WW. A suite five of kinetic inactivation models was fit to viral reverse transcription-qPCR reduction data, and model predicted CT values for 1, 2, and 3 log10 reduction of hNoV GI in municipal WW by free chlorine were 0.3, 2.1, and 7.8 mg-min/L, respectively. Model predicted CT values for reduction of hNoV GII in WW were 0.4, 2.0, and 7.0 mg-min/L, respectively. These results indicate that current WW treatment plant disinfection practices employing free chlorine are likely protective for public health with regards to noroviruses, and will achieve at least 3-log reduction of hNoV GI and GII RNA despite previous reports of high hNoV resistance.

Mechanism on Enhanced Nitrogen Removal in Municipal Secondary Effluent via Internal-Electrolysis Constructed Wetlands at Low Temperature in Winter

Aiming at the low pollutant removal efficiency of constructed wetlands (CWs) at low temperature in winter, three laboratory-scale vertical-flow CWs, namely unplanted CWs, ordinary CWs, and internal-electrolysis CWs, were used to investigate the nitrogen removal efficiency of municipal secondary effluent when the water temperature was 3-12℃. Moreover, the mechanism of enhanced denitrification of the new wetland was revealed through analysis of the microbial community diversity and community structure. The results showed that the internal-electrolysis CWs could make better use of the carbon sources in the municipal secondary effluent and had a higher removal rate. The effluent TN concentration was maintained at about (9±0.29) mg·L-1. The average TN removal rate was 42.27%, which was 17.91% and 17.33% higher than those of the unplanted CWs and ordinary CWs, respectively. The microbial activity was detected using fluorescein diacetate (FDA), and the result revealed that the microbial activity of the internal-electrolysis CWs could reach 0.224 mg·g-1, which was 2.6 times and 3.4 times of that of the unplanted CWs and ordinary CWs, respectively. The microbial denitrification intensity of the internal-electrolysis CWs was 2.8 times and 3.3 times of that of the unplanted and ordinary CWs, respectively. The results of high-throughput sequencing showed that the microbial community diversity of the internal electrolysis CWs was higher than those of the unplanted and ordinary CWs. Denitrification microorganisms were detected, mainly Dechloromonas, Rhizobium, Hyphomicrobium, and Rhodobacter, as well as Thiobacillus, which is an autotrophic denitrifying bacterium. There were obvious advantages in the total amount of denitrifying microorganisms in the internal-electrolysis CWs, as the denitrification microorganisms accounted for 7.13% of the total microbial biomass, which was 3.8 times and 8.7 times of that of the unplanted CWs and ordinary CWs, respectively.

Ozonation Characteristics of Low Coagulability Organic Matter from the Secondary Effluent of WWTPs

The aim of this study was to investigate the effectiveness of ozonation on the removal of organic matter with low coagulability from municipal secondary effluent. The results revealed that the removal efficiency of coagulation generally remained quite low. The residual organic matter belonged to low coagulability organic matter. The presence of the ozone increased the removal efficiency of color and UV254 gradually for low coagulability organic matter, whereas DOC had no noticeable change; the efficiencies were 45%, 34%, and 20%, respectively, at a dosage (denoted as O3/DOC) of 1.5 mg·mg-1. It could be concluded that ozone easily reacted with unsaturated organic matter, and the mineralization of organic matter was less effective. In order to further define the variation in organic matter of the secondary effluent, the differences between the relative molecular weight distribution and fluorescence characteristics of coagulation and ozonation with different zone dosages were monitored in this study. The findings showed that coagulation had little effect on organic content. Nonetheless, ozone might have preferentially reacted with high-molecular-weight substances of organic matter with low coagulability and reduced the fluorescence intensity in the humic-like regions significantly. The shift of fluorescence peak was not changed by ozonation. In addition, via X-ray photoelectron spectroscopy (XPS) analysis, it was identified that coagulation could remove carboxylic organic matter. On the other hand, with the increasing ozone dosage (from 0 to 1.5 mg·mg-1), ozone could preferentially react with low coagulability organic matter with aromatic structure, thus the amount of aliphatics increased gradually.

Study on operating flux of plate ceramic membrane treating municipal secondary effluent of WWTP

In recent years, plate ceramic membrane has been applied in the field of water and wastewater treatment successfully, because of its unique advantages. As an important parameter which can characterize properties of membrane, the water flux and critical flux of plate ceramic membrane treating municipal secondary effluent of Wastewater Treatment Plant(WWTP) were studied in this paper. And the flux change characteristics under different membrane pressure were obtained. The experimental results laid foundation for further exploring of mechanism of membrane fouling and related control techniques, and provided references for expanded application of plate ceramic membrane in wastewater reuse.