Presence of N, N'-Substituted p-Phenylenediamine Quinones in Tap Water: Implication for Human Exposure.

Monitoring studies have demonstrated the wide presence of N, N'-substituted p-phenylenediamine-derived quinones (PPDQs) in environmental matrices. The general population may be potentially exposed to PPDQs through the consumption of tap water. While, the existence of PPDQs in tap water has not been well examined. To fill this gap, in this study we collected tap water samples from Hangzhou, China, and examined seven homologues of PPDQs in collected samples. All target PPDQs were identified in the collected tap water samples, with distinct detection frequencies (38-89%). PPDQs detected in tap water was dominated by N-(1, 3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPDQ; mean 0.56 ng/L, < LOD-4.0 ng/L). The profiles of PPDQs concentrations in tap water from the four districts of Hangzhou city were slightly different. The daily intake (DI) was found highest for 6PPDQ (mean 14-22 pg/kg bw/day, median 10-15 pg/kg bw/day) through tap water intake. The relatively higher DIs of various PPDQs were displayed for infants (mean 10-22 pg/kg bw/day, median 6.5-15 pg/kg bw/day), relative to the children (8.0-18 pg/kg bw/day, 5.4-12 pg/kg bw/day) and adults (6.7-14 pg/kg bw/day, 4.5-10 pg/kg bw/day). These data are crucial for assessing the overall human exposure to PPDQs. This study first, to our knowledge, reveals the concentrations and profiles of PPDQs in tap water.

Effect of temperature on anoxic metabolism of nitrites to nitrous oxide by polyphosphate accumulating organisms.

Temperature is an important physical factor, which strongly influences biomass and metabolic activity. In this study, the effects of temperature on the anoxic metabolism of nitrite (NO2(-)) to nitrous oxide (N2O) by polyphosphate accumulating organisms, and the process of the accumulation of N2O (during nitrite reduction), which acts as an electron acceptor, were investigated using 91% +/- 4% Candidatus Accumulibacter phosphatis sludge. The results showed that N2O is accumulated when Accumulibacter first utilize nitrite instead of oxygen as the sole electron acceptor during the denitrifying phosphorus removal process. Properties such as nitrite reduction rate, phosphorus uptake rate, N2O reduction rate, and polyhydroxyalkanoate degradation rate were all influenced by temperature variation (over the range from 10 to 30 degrees C reaching maximum values at 25 degrees C). The reduction rate of N2O by N2O reductase was more sensitive to temperature when N2O was utilized as the sole electron acceptor instead of N2O, and the N2O reduction rates, ranging from 0.48 to 3.53 N20-N/(hr x g VSS), increased to 1.45 to 8.60 mg N2O-N/(hr x g VSS). The kinetics processes for temperature variation of 10 to 30 degrees C were (theta1 = 1.140-1.216 and theta2 = 1.139-1.167). In the range of 10 degrees C to 30 degrees C, almost all of the anoxic stoichiometry was sensitive to temperature changes. In addition, a rise in N2O reduction activity leading to a decrease in N2O accumulation in long term operations at the optimal temperature (27 degrees C calculated by the Arrhenius model).

Discovery of perfluoroalkyl sulfonyl quaternary ammonium substances in the environment and their environmental behaviors.

A variety of per- and polyfluoroalkyl substances (PFASs) have been released into the environment via wastewater treatment plant (WWTP) effluent, with current target and nontarget analytical methods typically focusing on negatively ionized PFASs while largely overlooking positively ionized ones. In this study, five cationic PFASs, perfluoroalkyl sulfonyl quaternary ammonium substances (PFAQASs), were first identified in surface water impacted by the WWTP effluent, applying a metabolomics-based nontarget analysis method. Environmental behaviors of identified novel PFAQASs were further investigated. In surface water, sediment, and fish (Coilia mystus) samples collected from the Yangtze River, 8:3 PFAQA was consistently the predominant PFAQASs, with the mean concentrations of 90 ng/L (< LOD-558 ng/L), 92 ng/g dw (< LOD-421 ng/g dw), and 2.3 ng/g ww (< LOD-4.6 ng/g ww), respectively. This study highlights the necessity to discover other cationic PFASs in the environment. Among PFAQASs, 8:4 PFAQA (4.2, range 3.4 - 4.6) had the highest mean sediment-water partitioning coefficient (log Koc), followed by 8:3 PFAQA (3.9, 2.8 - 4.5) and 6:3 PFAQA (3.7, 3.3 - 4.1). The log Koc of PFAQASs showed a general increase trend with the increasing carbon chain length. Mean bioaccumulation factor (BAF) values of PFAQASs calculated in the collected fish from the Yangtze River ranged from 1.9 ± 0.32 (4:3 PFAQA) to 2.9 ± 0.34 (8:4 PFAQA). The mean BAF values of PFAQASs generally increased with the carbon chain length. Further studies are warranted to elucidate the environmental fate, potential toxicity, and human exposure implications for these identified novel PFASs.

Research on catalytic denitrification by zero-valent iron (Fe0) and Pd-Ag catalyst.

This study primarily focused on how to effectively remove nitrate by catalytic denitrification through zero-valent iron (Fe0) and Pd-Ag catalyst. Response surface methodology (RSM), instead of the single factor experiments and orthogonal tests, was firstly applied to optimize the condition parameters of the catalytic process. Results indicated that RSM is accurate and feasible for the condition optimization of catalytic denitrification. Better catalytic performance (71.6% N2 Selectivity) was obtained under the following conditions: 5.1 pH, 127 min reaction time, 3.2 mass ration (Pd: Ag), and 4.2 g/L Fe0, which was higher than the previous study designed by single factor experiments and orthogonal tests, 68.1% and 68.7% of N2 Selectivity, respectively. However, under this optimal conditions, N2 selectivity showed a mild decrease (69.3%), when the real wastewater was used as influent. Further study revealed that cations (K+, Na+, Ca2+, Mg2+, and Al3+) and anions (Cl-, HCO3-, and SO42-) exist in wastewater could have distinctive influence on N2 selectivity. Finally, the reaction mechanism and kinetic model of catalytic denitrification were further studied.

Effect of Free Nitrous Acid on Nitrous Oxide Production and Denitrifying Phosphorus Removal by Polyphosphorus-Accumulating Organisms in Wastewater Treatment.

The inhibition of free nitrous acid (FNA) on denitrifying phosphorus removal has been widely reported for enhanced biological phosphorus removal; however, few studies focus on the nitrous oxide (N2O) production involved in this process. In this study, the effects of FNA on N2O production and anoxic phosphorus metabolism were investigated using phosphorus-accumulating organisms (PAOs) culture highly enriched (91 ± 4%) in Candidatus Accumulibacter phosphatis. Results show that the FNA concentration notably inhibited anoxic phosphorus metabolism and phosphorus uptake. Poly-ß-hydroxyalkanoate (PHA) degradation was completely inhibited when the FNA concentration was approximately 0.0923 mgHNO2-N/L. Higher initial FNA concentrations (0.00035 to 0.0103 mgHNO2-N/L) led to more PHA consumption/TN (0.444 to 0.916 mmol-C/(mmol-N·gVSS)). Moreover, it was found that FNA, rather than nitrite and pH, was likely the true inhibitor of N2O production. The highest proportion of N2O to TN was 78.42% at 0.0031 mgHNO2-N/L (equivalent to 42.44 mgNO2-N/L at pH 7.5), due to the simultaneous effects of FNA on the subsequent conversion of NO2 into N2O and then into N2. The traditional nitrite knee point can only indicate the exhaustion of nitrite, instead of the complete removal of TN.

[Impact on the microbial community of municipal sewage in the anammox system during the cooling process].

Anaerobic ammonium oxidation is an important part of the biological nitrogen removal process, and the performance of the process is determined by the microbial community structure. Low-temperature anaerobic ammonium oxidation technology has good prospects for saving a lot of energy, and anaerobic ammonium oxidation bacteria play a vital role in the removal of total nitrogen from waste water. To explore the microbial community structure changes of anammox reactor in sewage treatment during the cooling process (from 30 degrees C to 20 degrees), the total amount of the microbial, the quantity of anaerobic ammonium oxidation and the change of functional microbial community were investigated in a sewage treatment process using the phospholipid fatty acid method (PLFA), quantitative PCR and the clone library of bacterial 16S rRNA. The PLFAs results showed that the total amount of microbial was first decreased and then gradually increased with the running time, when the temperature dropped from 30 degrees C to 20 degrees C, and the NH4+ -N content in the effluent of the system was decreased. The quantitative PCR results showed that 16S rRNA gene copies of anammox bacteria increased from 1.19 x 10(8) copies x mL(-1) to 1.86 x 10(8) copies x mL(-1) in the wastewater. The PCR-DGGE results showed that when the temperature decreased, the anammox bacteria were further enriched. A shift of anammox bacteria community from single Candidatus Kuenenia sp. to a combination of Candidatus Brocadia sp. and Candidatus Kuenenia sp. was observed.

Biological nutrient removal by applying modified four step-feed technology to treat weak wastewater.

For weak municipal wastewater (COD ≤ 200 mg L(-1), NH(4)(+)-N ≤ 40 mg L(-1)) with low influent C/N, a pilot modified four step-feed process was applied for simultaneous biological nitrogen (N) and phosphorus (P) removal under different inflow distribution ratios. It was designed with a short hydraulic retention time of 8.7h to raise influent load, and the optimal effluent performance of COD, NH(4)(+)-N, total nitrogen (TN) and total phosphorus (TP) were 33.05, 0.58, 9.26 and 0.46 mg L(-1), respectively with inflow distribution ratio of 20:35:35:10%. More than 74% of carbon sources were utilized effectively for phosphorus release and denitrification. About 16.7% of TN was removed through simultaneous nitrification and denitrification in oxic zones. Moreover, the commendable sludge settling with a sludge loading of 0.04-0.1 kg COD/kg MLSS d, attributed to the higher mixed liquor suspended solids (MLSS) and the alternating anoxic/oxic operational mode. In addition, the pre-anoxic zone designed was beneficial for both nitrate reduction and anaerobic phosphorus release.