Microalgal Cultivation in Secondary Effluents:Enhancement of Algal Biomass,Nutrient Removal,and Lipid Productivity

The growth performance,nutrient removal,lipid accumulation and morphological changes of Cyanobacterium aponinum OUC1 and Scenedesmus obliquus which were cultured in secondary effluents from two wastewater treatment plants:Tuandao Wastewater Treatment Plant(ETD)and Licun River Wastewater Treatment Plant(ELR)were investigated.The results showed that both C.aponinum OUC1 and S.obliquus have superior growth performances in both undiluted effluents,while the better of them was that in ETD effluent,with cell densities of C.aponinum OUC1 and S.obliquus increased by 159%and 66%over that of BG11(control),respectively.Regarding nutrient removal,S.obliquus could completely remove inorganic phosphorus,and decrease ammonia nitrogen in ETD effluent by 81%.In addition,both C.aponinum OUC1 and S.obliquus cultivated in ETD exhibited extraordinary potential for biofuel production,increasing lipid productivities by 133%and 89%of that cultivated in ELR,respectively.As to ultrastructural changes,the differences in the lipoidal globules and glycogen granules of S.obliquus and C.aponinum OUC1 among the ETD and ELR treatments were mostly related to phosphorus limitations.The findings from this research reveal the probability using the secondary effluents as cultivation media to enhance algal biomass,nutrient removal and lipid productivity.

Impacts of electrochemical disinfection on the viability and structure of the microbiome in secondary effluent water

Electrochemical disinfection(ECD)is a promising disinfection technique for wastewater reclamation;however,the impacts of ECD on the microbiome in secondary effluent wastewater remain unknown.In this study,Propidium monoazide-qPCR(PMA-qPCR)and the plate count method were used to evaluate the inactivation performance,and the PMA-16S rRNA gene sequences of living cells were targeted to study the microbiome.A discrepancy was found between PMA-qPCR and the plate count method in the evaluation of cell count,with increases of 1.5 to 2.2 orders of magnitude in the disinfection rate after 150 s of disinfection.However,the cell count recovered and occasionally exceeded original levels within 3 d after disinfection.Biodiversity was suppressed after ECD,but the microbiome after 150 s disinfection retained a higher level of evenness and stability in the community with a median Shannon index(>3.7).Pathogenic bacteria remained high in relative abundance even after 150 s of 25 V disinfection,but the biofilm-forming population was effectively suppressed by ECD.The co-occurrence network revealed a centralized and fragile network as disinfection persisted,demonstrating the destabilizing effects of ECD on the microbiome.Functional pathways for cell membrane synthesis and organic compound degradation were enriched after ECD.The reaction of the microbiome after ECD was similar to other disinfection techniques in terms of community structure.

Degradation behavior of 17α-ethinylestradiol by ozonation in the synthetic secondary effluent

Endocrine disrupting chemicals（EDCs） in the secondary effluent discharged from wastewater treatment plants（WWTPs） are of great concern in the process of water reuse.Ozonation has been reported as a powerful oxidation technology to eliminate micropollutants in water treatment.Due to the complexity of the wastewater matrix,orthogonal experiments and single factor experiments were conducted to study the influence of operational parameters on the degradation of 17α-ethinylestradiol（EE2） in the synthetic secondary effluent.The results of the orthogonal experiments indicated that the initial ozone and natural organic matter（NOM） concentration significantly affected EE2 degradation efficiency,which was further validated by the single factor confirmation experiments.EE2 was shown to be effectively degraded by ozonation in the conditions of low pH（6）,NOM（10 mg/L）,carbonate（50 mg/L）,but high suspended solid（20 mg/L） and initial ozone concentration（9 mg/L）.The study firstly revealed that the lower pH resulted in higher degradation of EE2 in the synthetic secondary effluent,which differed from EDCs ozonation behavior in pure water.EE2 degradation by ozone molecule instead of hydroxyl radical was proposed to play a key role in the degradation of EDCs by ozonation in the secondary effluent.The ratio between O3 and TOC was identified as an appropriate index to assess the degradation of EE2 by ozonation in the synthetic secondary effluent.

Molecular characterization of effluent organic matter in secondary effluent and reclaimed water:Comparison to natural organic matter in source water

Municipal wastewater reclamation is becoming of increasing importance in the world to solve the problem of water scarcity. A better understanding of the molecular composition of effluent organic matter（Ef OM） in the treated effluents of municipal wastewater treatment plants（WWTPs） is crucial for ensuring the safety of water reuse. In this study, the molecular composition of Ef OM in the secondary effluent of a WWTP in Beijing and the reclaimed water further treated with a coagulation–sedimentation–ozonation process were characterized using a non-target Fourier transform ion cyclotron resonance mass spectrometry（FT-ICR MS） method and compared to that of natural organic matter（NOM） in the local source water from a reservoir. It was found that the molecular composition of Ef OM in the secondary effluent and reclaimed water was dominated by CHOS formulas, while NOM in the source water was dominated by CHO formulas. The CHO formulas of the three samples had similar origins. Anthropogenic surfactants were responsible for the CHOS formulas in Ef OM of the secondary effluent and were not well removed by the coagulation-sedimentation-ozonation treatment process adopted.

Mechanisms for simultaneous ozonation of sulfamethoxazole and natural organic matters in secondary effluent from sewage treatment plant

Sulfamethoxazole(SMX)is commonly detected in wastewater and cannot be completely decomposed during conventional treatment processes.Ozone(O_(3))is often used in water treatment.This study explored the influence of natural organic matters(NOM)in secondary effluent of a sewage treatment plant on the ozonation pathways of SMX.The changes in NOM components during ozonation were also analyzed.SMX was primarily degraded by hydrolysis,isoxazole-ring opening,and double-bond addition,whereas hydroxylation was not the principal route given the low maximum abundances of the hydroxylated products,with m/z of 269 and 287.The hydroxylation process occurred mainly through indirect oxidation because the maximum abundances of the products reduced by about 70%after the radical quencher was added,whereas isoxazole-ring opening and double-bond addition processes mainly depended on direct oxidation,which was unaffected by the quencher.NOM mainly affected the degradation of micropollutants by consuming•OH rather than O_(3)molecules,resulting in the 63%–85%decrease in indirect oxidation products.The NOM in the effluent were also degraded simultaneously during ozonation,and the components with larger aromaticity were more likely degraded through direct oxidation.The dependences of the three main components of NOM in the effluent on indirect oxidation followed the sequence:humic-like substances>fluvic-like substance-s>protein-like substances.This study reveals the ozonation mechanism of SMX in secondary effluent and provides a theoretical basis for the control of SMX and its degradation products in actual water treatment.

Acute effects of chlorpyryphos-ethyl and secondary treated effluents on acetylcholinesterase and butyrylcholinesterase activities in Carcinus maenas

The acute effects of commercial formulation of chlorpyrifos-ethyl （Dursban ） and the secondary treated industrial/urban effluent （STIUE） exposure on acetylcholinesterase （ACHE） and butyrylcholinesterase （BuChE） activities in hepatopancreas and gills of Mediterranean crab Carcinus maenas were investigated. After 2 d of exposure to chlorpyriphos-ethyl, the AChE activity was inhibited in both organs at concentrations of 3.12 and 7.82 μg/L, whereas the BuCHE was inhibited only at higher concentration 7.82 μg/L of commercial preparation Dursban~. The exposure of crabs to Dursban （3.12 μg/L） showed a significant decrement of ACHE activity at 24 and 48 h, whereas the BuChE was inhibited only after 24 h and no inhibition for both enzymes was observed after 72 h. Moreover, a significant repression of AChE activity was observed in both organs of C. maenas exposed to 5% of STIUE. Our experiments indicated that the measurement of AChE activity in gills and hepatopancreas of C. maenas would be useful biomarker of organophosphorous （OP） and of neurotoxic effects of STIUE in Tunisia.

Characteristics of contaminants in water and sediment of a constructed wetland treating piggery wastewater effluent

Constructed wetland （CW） is the preferred means of controlling water quality because of its natural treatment mechanisms and function as a secondary or tertiary treatment unit. CW is increasingly applied in Korea for secondary effluent of livestock wastewater treatment. This study was conducted to recognize the characteristics of contaminants in the accumulated sediment at the bottom soil layer and to reduce the phosphorus release from sediments of the free water surface CW for the treatment of secondary piggery wastewater effluent from a livestock wastewater treatment facility. The results revealed that the dominant phosphorus existence types at near the inlet of the CW were non-apatite phosphorus （59%） and residual phosphorus （32%） suggesting that most of the particles of the influent are made up of inorganic materials and dead cells. Sediment accumulation is important when determining the long-term maintenance requirements over the lifetime of CW. Continuous monitoring will be performed for a further assessment of the CW system and design.

Dissolved organic matter removal using magnetic anion exchange resin treatment on biological effluent of textile dyeing wastewater

This study investigated the removal of dissolved organic matter（DOM） from real dyeing bio-treatment effluents（DBEs） with the use of a novel magnetic anion exchange resin（NDMP）.DOMs in two typical DBEs were fractionized using DAX-8/XAD-4 resin and ultrafiltration membranes. The hydrophilic fractions and the low molecular weight（MW）（〈3 kDa） DOM fractions constituted a major portion（〉50%） of DOMs for the two effluents. The hydrophilic and low MW fractions of both effluents were the greatest contributors of specific UV254absorbance（SUVA254）,and the SUVA254 of DOM fractions decreased with hydrophobicity and MW. Two DBEs exhibited acute and chronic biotoxicities. Both acute and chronic toxicities of DOM fractions increased linearly with the increase of SUVA254 value. Kinetics of dissolved organic carbon（DOC） removal via NDMP treatment was performed by comparing it with that of particle active carbon（PAC）. Results indicated that the removal of DOC from DBEs via NDMP was 60%,whereas DOC removals by PAC were lower than 15%. Acidic organics could be significantly removed with the use of NDMP. DOM with large MW in DBE could be removed significantly by using the same means. Removal efficiency of NDMP for DOM decreased with the decrease of MW. Compared with PAC,NDMP could significantly reduce the acute and chronic bio-toxicities of DBEs. NaCl/NaOH mixture regenerants,with selected concentrations of 10% NaCl（m/m）/1%NaOH（m/m）,could improve desorption efficiency.

Catalytic ozonation treatment of papermaking wastewater by Ag-doped NiFe2O4 : Performance and mechanism

The catalytic ozonation treatment of secondary biochemical effluent for papermaking wastewater by Ag-doped nickel ferrite was investigated.Ag-doped catalysts prepared by sol-gel method were characterized,illustrating that Ag entirely entered the crystalline of Ni Fe2O4 and changed the surface properties.The addition of catalyst enhanced the removal efficiency of chemical oxygen demand and total organic carbon.The results of gas chromatography-mass spectrometer,ultraviolet light absorbance at 254 nm and threedimensional fluorescence excitation-emission matrix suggested that aromatic compounds were efficiently degraded and toxic substances,such as dibutyl phthalate.In addition,the radical scavenging experiments confirmed the hydroxyl radicals acted as the main reactive oxygen species and the surface properties of catalysts played an important role in the reaction.Overall,this work validated potential applications of Ag-doped Ni Fe2O4 catalyzed ozonation process of biologically recalcitrant wastewater.

Removal efficiencies of natural and synthetic progesterones in hospital wastewater treated by different disinfection processes

Progesterones are ubiquitous in hospital wastewater(HWW)with concentrations much higher than those of estrogens and androgens.To ensure that these water systems are safe to use,disinfection is crucial during HWW treatment by providing"front line"defense against biological contaminations.Here,five disinfection processes,namely,chlorine(Cl_(2)),chlorine dioxide(ClO_(2)),ozone(O_(3)),ultraviolet(UV)),and UV/chlorine(UV/Cl_(2)),were selected to investigate their removal efficiencies for progesterones in primary filtration and secondary biological treatment effluents.There were 61 natural and synthetic progesterones detected in HWW,with the natural progesterones being the main components with a concentration of 845.51 ng/L and contributing to 75.08%of the total proge-sterones.The primary filtration treatment presented insignificant removal effects on the progesterones,while the secondary biological treatment significantly reduced the progesterone content by biode-gradation.The order of removal efficiencies of total progesterones by different disinfection processes was UV/Cl_(2)>Cl_(2)>O_(3)>ClO_(2)>UV.UV/Cl_(2)showed the highest removal efficiency against progesterones mainly due to the activation of Cl_(2)by ultraviolet(UV)photolysis,which helps open the heterocyclic,aromatic,and phenolic rings,thus accelerating progesterone degradation.In addition,the removal efficiencies of natural progesterones in the five disinfection processes were higher than those of synthetic progesterones(progesterone derivatives,19-nortestosterone derivatives,and 17α-hydroxyprogesterone derivatives).