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As carbon sources for the denitrification process, agricultural wastes have some problems, such as excess release of organic carbon; unclear release characteristics of nitrogen, phosphorus, and colorimetric substances; and unclear components, release mechanisms, and potential effects of the released dissolved organic matter (DOM) in the start-up period. To resolve those problems, rice straw, wheat straw, corn stalk, corncob, soybean stalk, and soybean hull were selected as denitrification carbon sources to investigate the release mechanisms and potential influences of the organic matter, secondary pollutants, and DOM. The results showed that the six agricultural wastes could be used as the denitrification carbon source. The carbon content in the wheat straw was the highest and the secondary pollution risk from the corncob was the lowest. For the six carbon sources, the second-order kinetic equation and Ritger-Peppas equation were followed during the 1-120 h carbon release process. The fitting results demonstrated that corncob was more suitable for use as the denitrification carbon source because of its moderate c m value and longer t 1/2 value, and the release mechanisms of the six types of carbon sources were mainly controlled by the diffusion process. The NH 4 + -N, TN, and TP contents in the immersion water of the rice straw were higher than those of the five other agricultural wastes, and there was heavy chromaticity in the immersion water of the wheat straw and corn stalk. The amounts of nitrogen, phosphorus, and chromatic substances released from the corncob were the lowest. The leachates of the corncob and soybean hull had higher biodegradability and lower risks of secondary pollution than those of the other sources. The aromaticity and molecular weight of DOM increased as the reaction time increased, and the humification of DOM was low. Five components were identified by PARAFAC. The main component was protein-like matter, which was mainly composed of tyrosine-like and tryptophan-like substances. There was less humic acid-like matter in the immersion water. The component characteristics of DOM might have had an adverse effect on the subsequent water treatment process. These results could provide theoretical support for the impact on effluent water quality and risk assessment when the agricultural wastes are used as an additional denitrification carbon source at the start-up stage.

When low-concentration rural sewage is treated biologically, the effluent total nitrogen (TN) concentration often does not meet the discharge limit because of its low carbon-to-nitrogen ratio (C/N). To solve this problem, a laboratory-scale anoxic/oxic (A/O) biofilter packed with Arundo donax and activated carbon as the anoxic and aerobic column fillers (No. 2) was operated for treatment of simulated rural sewage and advanced nitrogen removal, while an ordinary gravel-packing A/O biofilter (No. 1) was set up as the control group. The results were as follows. When the influent chemical oxygen demand (COD), ammonia nitrogen (NH 4 + -N), and TN concentrations were (79.47±14.21), (34.49±2.08), and (34.73±3.87) mg·L -1 , respectively, the No. 1 and No. 2 reactors achieved removal efficiencies of (88.00±7.00)% and (89.00±10.00)%, (90.00±2.00)% and (97.00±7.00)%, and (37±15)% and (68±7)%, respectively. The results revealed that using Arundo donax and activated carbon new fillers could significantly enhance NH 4 + -N and TN removal. High-throughput sequencing results indicated that the microorganisms involved in the nitrification process in the No. 1 reactor mainly belong to Proteobacteria, whereas those in the No. 2 reactor belong to Proteobacteria and Nitrospirae. In addition, the main denitrification bacterial phyla in the anoxic column of the No. 1 reactor were Chloroflexi, Proteobacteria, Bacteroidetes, and Planctomycetes, whereas those in the anoxic column of the No. 2 reactor were primarily Bacteroidetes, Proteobacteria, Firmicutes, and Patescibacteria. Quantitative real time polymerase chain reaction (qPCR) results showed that the microbial nitrification ( amoA and Nitrospira 16S rDNA), denitrification ( narG , nosZ , nirS , and nirK ), and anaerobic ammonium oxidation functional genes (ANAMMOX) in the No. 2 reactor were significantly higher than those in the No. 1 reactor. All the genes, except for the narG and nosZ genes, had one to two orders of magnitude of improvement in the No. 2 reactor compared to those in the No. 1 reactor.

This study assesses the spatial distribution characteristics and ecological risk of phthalate esters (PAEs) in the surface sediments of the mainstream and tributaries of the Songhua River, China, using concentrations and composition of six PAEs, which were analyzed using gas chromatography-mass spectrometery (GC-MS). We assess the ∑ 6 PAEs ecological risk using the hazard quotient (HQ) method and environmental risk levels (ERL). The results were as follows. ① It was found that the total concentrations of ∑ 6 PAEs ranged from 6832.5 to 36298.9 ng·g -1 dry weight (average 18388.6 ng·g -1 ), with the main contributions coming from di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP). The difference between the main stream ∑ 6 PAEs (6832.5-36298.9 ng·g -1 , average 18616.9 ng·g -1 ) and the tributary ∑ 6 PAEs (10367.6-26593.3 ng·g -1 , average 18264.1 ng·g -1 ) was not significant ( P >0.05). The mean concentrations of individual PAEs in the tributary stream differed little from that of the main stream. The ∑ 6 PAEs concentration of the Songhua River decreased initially but then increased from the upstream to the downstream. The average ∑ 6 PAEs concentration in natural agricultural areas (18677.5 ng·g -1 ) was similar to that found in urban industrial areas (18063.7 ng·g -1 ), and DBP and DEHP contributed 98% of ∑ 6 PAEs. ② The main sources of ∑ 6 PAEs were domestic, agricultural production, and industrial production using plasticizers. ③ The ecological risk assessment indicated that DMP and BBP in the surface sediments of the Songhua River did not pose an ecological risk for aquatic organisms, and that DEP was associated with a low ecological risk, whereas DEHP and DBP posed a high ecological risk for aquatic organisms.

The objective of this experiment was to investigate the influence of SO 3 2- dosage, pH value, initial perfluorooctane sulfonate(PFOS)concentration as well as coexisting substances on the degradation and defluorination of PFOS by VUV-SO 3 2- process. The results indicated that the increase of SO 3 2- dosage could lead to rise in the concentration of active species hydrated electron(e aq - ) and thus enhance the degradation and defluorination of PFOS. As the concentration of SO 3 2- increased from 1 mmol·L -1 to 20 mmol·L -1 , the degradation and defluorination rates of PFOS increased from 45% and 40% to 97% and 63%, respectively. The degradation and defluorination of PFOS were also enhanced with the increment of the solution pH values, and the defluorination was more sensitive to the pH values. In addition, more PFOS was degraded with the increase of initial PFOS mass concentration, although the degradation and defluorination rates of PFOS were reduced. When the initial PFOS mass concentration changed from 1 mg·L -1 to 50 mg·L -1 , the degradation amount of PFOS after four hrs increased by about 50 times, probably due to the higher utilization proportion of e aq - at high pollutants concentration. Last but not least, the influence of co-existing substances, Cl - and HCO 3 - , on PFOS degradation could be neglected, whereas their effects on defluorination were observed. Defluorination of PFOS was enhanced with the increased Cl - concentration, however, increased first and then decreased with the increment of HCO 3 - concentration. It was also found that the presence of humic acid(HA) lowered degradation as well as defluorination of PFOS owing to the blockage of effective UV light and trapping of active species for photochemical reaction.

The efficiency of iron chloride on simultaneous denitrification and chemical-biological flocculation process was investigated through a lab-scale study. The results showed that: there were not significant differences in the denitrification rate, COD and NO3(-) -N removal efficiency between the control reactor and the denitrification reactor with the dosage of 20 mg x L(-1) Fe after 14 days' domestication. Meanwhile the TP removal efficiency was increased to over 80%. Though sludge concentration was increased by adding FeCl3, the settling performance wasn't change because the sludge density was increased and the particle size was reduced. The sludge settling volume (SV30) and specific resistance of filtration (SRF) after adding FeCl3 were only 22% and 1.5 x 10(12) m x kg(-1), which were lower than the values in the control reactor and benefit for sludge treatment.

A bench-scale comparative study between gas-water alternative membrane bioreactor (AMBR) and traditional submerged membrane bioreactor (SMBR) treating synthetic municipal wastewater was conducted with respect to the effects of carbon and nitrogen removal and membrane fouling. The results showed that both the AMBR and the SMBR had very good removal in COD and NH4+ -N of more than 96%. In SMBR, carbon and nitrogen removal was enabled by biomass in bulk liquid, while in AMBR, it was supposed to be functioned mainly by the biofilm attached to the surface of hollow fiber membrane since little sludge was found in the bulk liquid. However, TN removal was 76.94% in AMBR and 52.41% in SMBR, showing a more effective denitrification in AMBR compared to SMBR. Also, AMBR was found to be more effective in membrane fouling alleviation than SMBR through long time investigation of trans-membrane pressure.

A long-term operation was conducted to investigate the alleviation of membrane fouling by sludge/water pre-separation membrane bioreactor (S/W-MBR). The variation of trans-membrane pressure (TMP), concentration of sludge and extracellular polymeric substances (EPS) on S/W-MBR and submerged membrane bioreactor (SMBR) was also studied. The results showed that the sludge concentration in S/W-MBR was basically identical with that of SMBR's biotic area, while the sludge concentration was significantly decreased in S/W-MBR's membrane area than that of SMBR's. The concentration of EPS was increased with operation time in both two MBRs' biotic area, but it was lower and basically maintained at the level of 15 mg/g in S/W-MBR's membrane area. The S/W-MBR was more capable of alleviating membrane fouling, and it had been cleaned only 2 times while the SMBR who had been cleaned 5 times during the period of about 90 days laboratory performance.

Crystal violet (CV) adsorption from aqueous solution on activated sludge (AS) and powdered activated carbon (PAC) was comparatively studied through batch jar tests. It was found that the adsorption isotherm of CV on AS satisfied both Langmuir and Freundlich models, while the adsorption of CV on PAC satisfied Freundlich model more than Langmuir model. The maximum adsorption capacity of CV on AS was 571.26 mg x g(-1), much higher than that on PAC, which was only 131.09 mg x g(-1). The adsorption of CV on AS was analyzed using pseudo first-order and pseudo second-order adsorption kinetic models, and the pseudo second-order kinetic model could better describe the adsorption. The impacts of stir speed and the ratio of AS/CV on CV adsorption were also investigated. Stir speed showed no effect on equilibrium CV concentration. At the AS/CV ratio of 10 : 1, the equilibrium CV concentration increased with increasing initial CV concentration, while the initial CV concentration showed no influence on equilibrium CV concentration at the AS/CV ratio of 20 : 1 or 50 : 1.