[Pollution Characteristics and Source Apportionment of Atmospheric VOCs During Ozone Pollution Period in the Main Urban Area of Chongqing].

In late August 2020, a period of O3 pollution occurred in the main urban area of Chongqing and lasted for approximately 2 weeks (till early September). Ambient air samples, collected using Summa Canisters and DNPH sampling columns at three observation sites in the main urban area, were used to study the composition, photochemical reaction activity, and source apportionment of volatile organic compounds (VOCs) during the period of O3 pollution. The results showed that the mean volume fraction of TVOCs in the main urban area of Chongqing during the observation period was 45.08×10-9, and the components were ranked by volume fraction in the following order:OVOCs, alkanes, halohydrocarbons, alkenes, aromatics, and alkynes. Formaldehyde, ethylene, and acetone made up the higher volume fraction of VOCs, together accounting for more than 30% of TVOCs. OVOCs and alkenes contributed more to · OH loss rate (Li·OH) and ozone formation potential (OFP) and were the key VOCs components for ozone generation. The main active species in the OVOCs component were formaldehyde, acetaldehyde, and acrolein; the main active species in the alkene component were isoprene, ethylene, and n-butene. The ratio of xylene to ethylbenzene in VOCs was low, and they showed a significant correlation, indicating that the VOCs air mass in the main urban area was highly aging and affected by long-distance transmission from other areas. The source apportionment results of the PMF model showed five main sources of VOCs, namely secondary generation (27.67%), vehicle exhaust (26.56%), industrial emission (17.86%), plant (14.51%), and fossil fuel combustion (13.4%).

[Effects of Organic Substrates on ANAMMOX-MFC Denitrification Electrogenesis Performance].

An anaerobic ammonium oxidation microbial fuel cell (ANAMMOX-MFC) was successfully started by inoculating anaerobic ammonium oxide sludge into the anode of a microbial fuel cell and then used to study the effect of glucose and phenol on ANAMMOX-MFC denitrification electrogenesis performance. The results showed that the ANAMMOX bacteria promoted ANAMMOX-MFC denitrification when the concentration of glucose was low (100-200 mg·L-1). At that time, the chemical oxygen demand (COD) concentration of the reactor was not significant. The electrogenesis production performance and NH4+-N removal rate gradually decreased when the glucose concentration was higher than 300 mg·L-1, but the NO2--N removal rate generally remained unchanged. The COD concentration was also reduced, indicating that the activity of the ANAMMOX bacteria was inhibited and the activity of denitrification bacteria began to increase. The polarization curve fitting degree was low, and the change in COD concentration had little effect on the battery internal resistance. When the concentration of phenol was low (50-100 mg·L-1), there was little effect on ANAMMOX-MFC denitrification electrogenesis performance. When the concentration of phenol exceeded 200 mg·L-1, ANAMMOX-MFC denitrification performance was gradually inhibited. Overall, in the process, the COD concentrations of the water influent and effluent changed little, the polarization curve fitting degree was low, and the apparent internal resistance increased slowly.

[Characteristics of Nitrobacteria in SBR with Trace N2H4 Addition].

A sequencing batch reactor (SBR) was conducted to perform nitrification process. The influence of long-term trace hydrazine (N2H4) addition (about 3 mg·L-1) on ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in nitrifying sludge was investigated. The result indicated that Nitrosococcu, Nitrosomonas and Nitrosospira were related to AOB, and Nitrobacter was related to NOB in nitrifying sludge with N2H4 addition, respectively. The estimates of AOB population (in dry sludge) with N2H4 addition decreased from 1.0×109 to 2.09×104 copies·g-1, and those of NOB decreased from 1.28×107 to 2.56×105 copies·g-1. AOB was more sensitive to environmental factors than NOB, the effect of inhibition and toxicity on nitrobacteria caused more loss of AOB abundances than that of NOB, but quantitative real-time PCR could not determine the inhibition of N2H4 on microbial activity of AOB and NOB. The nitrobacteria activity was destroyed with long-term trace N2H4 addition, and the reactor collapsed. Consequently, it was possibly unable to inhibit NOB activity by controlling the added N2H4 concentration, and further take off NOB in nitrification process for improving nitrogen removal.

[Polyhydroxyalkanoate (PHA) Synthesis by Glycerol-based Mixed Culture and Its Relation with Oxygen Uptake Rate (OUR)].

Polyhydroxyalkanoate (PHA) is one of the most promising biopolymers with the advantages of biodegradable biocompatible and renewable. A glycerol-fed PHA-producing mixed culture was enriched in a feast-famine regime. The substrate versatility and PHA production capacity of the mixed culture were studied using acetate,propionate,butyric, glucose and lactate as substrate, respectively. The results showed a high PHA content with lactate and acetate as the sole substrate, respectively. When acetate and propionate were used as mixed substrates to produce PHA, the PHA contents increased with the proportion of acetate and the PHA content was the highest as the ratio acetate/propionate was 3:1.The results based on the modeling of simultaneously storage and growth and the linear fitting under three different acetate/propionate ratios showed that there was a linear relation between PHA synthesis and OUR. Thus, it is feasible to estimate PHA content based on in-situ real-time monitoring data of OUR.

[On-line Estimation for the Amount of Stored PHA in Activated Sludge Based on OUR-HPR Measurements].

Activated sludge process is an important approach for industrial Polyhydroxyalkanoate ( PHA ) production. Off-line measurement with a time lag and complex analysis, is a common method for PHA, but is not suitable for the process control of PHA production. Based on a model for simultaneous storage and growth-soluble microbial products (SSAG-SMP), it is assumed that there is the linear relationship between the PHA synthesized and OUR or HPR, respectively. Further, a novel method to estimate PHA content based on in-situ monitoring data of oxygen uptake rate (OUR) and hydrogen-ion production rate (HPR) is established in this paper. The results of modeling OUR and HPR under different substrate concentrations showed that oxygen consumption proportion (kPHA,OUR) and proton consumption proportion (kPHA,HPR) of PHA synthesis were 0.67 and 0.57, respectively. The predicted results based on the linear relationship were essentially consistent with measured ones, and indicated that the method is feasible

[Influencing factors of floc size distribution and fractal dimension of activated sludge].

Floc size distribution (FSD) and fractal dimension are the important parameters for activated sludge. FSD of aerobic activated sludge during flocculation process was measured by a laser particle size analyzer, and the influence of velocity gradient, VSS/ SS, EPS content and Zeta potential on FSD was investigated. The results showed that the floc volume-average size was negatively correlated to velocity gradient (R > 0. 80) , and the order-of-magnitude of the floc volume-average size was equivalent to that of Kolmogorov scale (their differences were dependent on sludge VSS/SS, floc strength and etc). At a fixing velocity gradient, the floc volume-average size was positively correlated to VSS/SS or EPS (R2 >0. 85) , whereas negatively correlated to Zeta potential. Organic matter and EPS played important roles on the flocculation of activated sludge by enhancing the floc strength and improving the flocculation effect. Compared with polysaccharides, proteins in EPS seemed to be more beneficial for the flocculation of activated sludge. Based on microscopy and image analysis, the 2D and 3D fractal dimension of aerobic activated sludge floc was determined to be 1.28-1.72 and 1.70-2.69, respectively. It was found that fractal dimension (2D and 3D)was decreased with increasing VSS/SS (or EPS content). For the same activated sludge, the 3D fractal dimension was decreased with increasing floc size, and the relationship between 3D fractal dimension and floc size could be approximately described by a power function.

The enhancement of completely autotrophic nitrogen removal over nitrite (CANON) by N2H4 addition.

The long-term addition of N2H4 to completely autotrophic nitrogen removal over nitrite (CANON) sequencing batch reactors (SBRs) recovered and enhanced their autotrophic nitrogen removal capacity while simultaneously reducing their production of NO3(-). The total nitrogen (TN) removal rate and TN removal efficiency of the process increased from 0.202±0.011 to 0.370±0.016 kg N/m(3)/d and from 65.1±3.75% to 77.4±3.8%, respectively, and the molar ratio of NO3(-) production to NH4(+) removal (MRNN) decreased to 0.058. The most effective concentration of N2H4 addition was approximately 3.99 mg/L. N2H4 could increase the specific growth rate of anaerobic ammonium-oxidizing bacteria (AnAOB) and inhibit aerobic ammonia oxidation. The electrons released from the oxidation of additional N2H4 using hydrazine dehydrogenase (HDH), which substituted the electrons from NO2(-) oxidation to NO3(-), replenished the consumption of AnAOB anabolism and significantly reduced the consequent NO3(-) production.

[Monitoring the stoichiometric relation of ammonium oxidation with the titrimetry of hydrogen ion variation].

A set of automatically titrimetric system to monitor the hydrogen ion variation during biological wastewater treatment process in a batch bioreactor was developed, which consists of a batch bioreactor, data auto-acquisition and preservation unit, and titrant autodosing unit. The accuracy of measurement for the system was evaluated by measuring the stoichiometric ratio of hydrogen ion production amount to ammonium consumption amount of ammonium oxidation in an activated sludge system. The ratios measured in a 1L bioreactor with NH4+ -N concentrations of 1.67, 3.33, 8.33, 16. 66 and 30.00 mg/L as N respectively were very close to the theoretical value, and the relative errors were among 2.09%-6.34%. However, the relative errors in bioreactors of 1, 2, 3 and 4 L with NH4+ -N concentration of 16.66 mg/L as N were among 2.09%- -18.57%, and increased significantly with accretion of the volume of bioreactor. The buffers of bicarbonate and the ammonium, especially the titrimetric dynamic effects in a larger bioreactor are the primarily factors resulting in errors. This study provides an important approach for monitoring hydrogen ion variation in the process of biological wastewater treatment by titrimetry.

[Simultaneous chracterization of RBCOD and SBCOD in wastewater by hybrid respirometer].

Respirometry was made using wastewater and activated sludge from a WWTP of Chongqing through self-developed hybrid respirometer. And complete oxygen uptake rate (OUR) curves containing OUR of biodegradation process of RBCOD and SBCOD and endogenous process were obtained. A new method based on respirometry was proposed to characterize RBCOD and SBCOD in wastewater simultaneously, in which hydrolysis model was selected to analyze OUR curves of SBCOD according to the two-phases nature of exogenous OUR and trend-test method for endogens OUR. Compared with the traditional OUR-stages method, the new method reduces the man-made error and improves the accuracy of wastewater COD fractions characterization.