Kinetics and removal formula of methyl mercaptan by ethanol absorption without neglecting solute accumulation.

The wet scrubbing process is commonly adopted for organic odor treatment. In this study, methyl mercaptan (CH3SH) was selected as a representative hydrophobic organic odorant which was treated using an ethanol solution in a scrubbing tower. Results showed that the ethanol solution can retain the ideal CH3SH removal effect for 2.0 h. The following experimental conditions were set: intake load of 4,700 m3 m-2 h-1, spraying load of 5,100 L m-2 h-1, and volume ratio of ethanol/water at 1:5. The solute accumulation of CH3SH in the scrubbing liquid exceeded 3.01 × 10-4 kmol CH3SH/kmol ethanol when the scrubbing tower operated for more than 2.0 h. The mathematical formula which neglected solute accumulation in the ethanol solution exhibited poor adaptability to the removal effect of CH3SH by ethanol absorption. The CH3SH removal effect of solute accumulation in the ethanol solution was explored in long-term operation. Meanwhile, the CH3SH removal rate formula which considered solute accumulation in the ethanol solution could be calculated as η = a'-b'X2/Y1. The kinetic parameters of the formula fitting results were phase equilibrium constant m 0.0076, and overall mass transfer coefficient KY 4.98 kmol m-2 h-1 in the scrubbing tower. These findings can serve as a reference for engineering design and operation for the removal of CH3SH by ethanol absorption.

[Influencing Factors for Phosphorus Removal by Modified Bio-ceramic Substrates Coated with ZnAl-LDHs Synthesized by Different Modification Conditions].

Under different pH conditions, the hydrothermal and co-precipitation method was used to synthesize layered double hydroxides (LDHs) coated on bio-ceramic substrates with three different Zn2+/Al3+ molar ratios. Applying the original and six kinds of modified bio-ceramic substrates coated with ZnAl-LDHs (bio-ceramic/ZnAl-LDHs) in simulated vertical-flow constructed wetlands, experiments for phosphorus removal and isothermal adsorption were conducted to analyze the mechanism and effect of each synthesis factor. The results showed that ZnAl-LDHs (pH=11) had a more obvious effect on phosphorus removal, especially for bio-ceramic/ZnAl-LDHs (pH=11, 1:1), whose average removal rates of TP, TDP and SRP were enhanced over 70%. Its maximum adsorption capacity for phosphorus was three times higher than that of the original bio-ceramic. Both pH and Zn2+/Al3+ molar ratio affected the configuration and coating properties of bio-ceramic/ZnAl-LDHs at the time of synthesis, and pH was the main synthesis factor for phosphorus removal efficiency of bio-ceramic/ZnAl-LDHs. Through reasonable regulation of pH and Zn2+/Al3+ molar ratio when bio-ceramic/ZnAl-LDHs was synthesized, the phosphorus removal efficiency could be improved effectively.

[Effects of NO3--N Loading on the Early-Period Efficiency of Denitrification and Carbon Releasing in Constructed Wetland Filled with Bark].

The reuse of tailwater as recycled water requires an advanced nitrogen removal treatment, during which carbon source is added based on the tailwater quality. This study conducted an advanced nitrogen removal model test in constructed wetland to evaluate the effects of influent NO3--N loading on denitrification and carbon releasing. In the constructed wetland, bark was used as filler and carbon source for nitrogen removal. The results showed that nitrogen removal was steady in the constructed wetland filled with bark. Denitrification velocity followed the Monod equation, and it increased as the influent NO3--N loading increased. The saturation constant KS was 19.10 mg·L-1. NO3--N removal rate decreased as the influent NO3--N loading increased. During the early periods of operating the constructed wetland filled with bark, the carbon releasing amount and velocity increased as the influent NO3--N loading increased. Both factors were positively linearly correlated with the influent NO3--N loading. The static carbon releasing velocity was 0.2 mg·(g·d)-1. Compared with the hollow and loose plant carbons, such as rotten wood, bark had a better performance and a longer cycle of carbon releasing, which made bark a good slow-release carbon source.

[Control strategies of nitrogen removal process in a pilot test of the southern WWTP based on the nitrogen balance].

By building the mass balance of nitrogen in A2/O process, the nitrogen model which raised some strategies on how to control sludge return ratio and mixed liquid return ratio to make the effluent nitrogen achieve the national standard A under different influent total nitrogen (TN) , was set up. And the presumed parameters were verified by the pilot test of the Wuhan's Longwangzui WWTP. The result showed that when the temperature and the TN were over 15 degrees C and below 30 mg x L(-1) respectively, the mixed liquid return ratio was 0. When the temperature was between 10 degrees C and 15 degrees C and TN was over 30 mg x L(-1), higher MLSS and DO elevated N removal. When the temperature was far below 10 degrees C, the mixed liquid return ratio was also at a higher level. Based on the Wuhan's Longwangzui WWTP influent water quality, measures of adjusting the return ratio were well adapted to obtain acceptable nitrogen effluent.

[Characteristics of nitrification and denitrification for simultaneous nitrogen and phosphorus removal by granular sludge].

In the alternating anaerobic/aerobic SBR reactor,the nitrification and denitrification characteristics of simultaneous nitrogen and phosphorus removal by granular sludge were studied. The results of batch experiments indicated that the maximal nitrification rate, denitrification rate, anoxic phosphorus uptake and denitrification rate were 14.13 mg x (g x h))-1), 34.89 mg x (g x h)/(-1) and 13.11 mg x (g x h)(-1), respectively. In SBR, the maximal nitrification rate and denitrification rate were 4.60 mg x (g x h)(-1) and 1.43 mg x (g x h)(-1), respectively, which were lower than those in the batch test. The amount of nitrogen removal by the simultaneous nitrification and denitrification process was approximately 232.5 mg x d(-1), which was 54.3% of the total nitrogen removal. The removal efficiency of N and P was about 90% and 95%, respectively. The simultaneous nitrogen and phosphorus removal by granular sludge showed high efficiency in nitrogen and phosphorus removal.

[Preliminary study on denitrification capacity of constructed wetlands filled by bark].

Constructed wetlands have been widely used for the treatment of outlets of municipal wastewater treatment plants, treatment of agricultural pollution etc, adequate carbon is a very good source for denitrification and it is very crucial for improving the removal rate of nitrate nitrogen in constructed wetlands. An attempt has been made to workout for the nitrate removal by the integrated vertical constructed wetland, the bark was used for carbon source, the results shows the denitrifying bacteria in the constructed wetlands can utilize the carbon source very well, produced by bark to remove nitrate nitrogen. The efficiency of denitrification increases with the increase of the hydraulic loading and the influent nitrate loading,but the rate of the nitrate nitrogen removal decreases. At the condition of influent NO3(-)-N of 50 mg/L and the hydraulic loading of 0.1 m3/(m2 x d), the removal rate of nitrate nitrogen in the wetland system is around 80%. The suitable pH is 7 to 8 and when the pH is out of this range, it restricts the denitrification process.

[Formation of the phosphorus removal granular sludge and phosphorus removal characteristics of the anaerobic/oxic and anaerobic/anoxic/oxic granular sludge process in SBR].

Phosphorous removal & denitrifying phosphate uptake of the granular sludge was investigated in this study. Inoculated with flocculation sludge, the granulation of the biological phosphorous removal sludge was realized in a sequencing batch reactor (SBR) fed with sodium acetate by means of hydraulic selection under an anaerobic/oxic alternating operation (referred to as an A/O). Then the biological phosphorous removal granular sludge was induced into the denitrifying phosphate uptake granular sludge under an anaerobic/anoxic/oxic alternating operation (referred to as an A/A/O). The properties of the two kinds of granular sludge were studied. The biological phosphorus removal granular sludge was completed on the 82nd day. The biological phosphorus removal granule sludge showed some characteristics, e.g. pallideflavens in color, 0.5-1.5 mm in diameter, 20-30 m/h in settling velocity, 94% in water content, 1.043 9 in specific gravity, and below 50 mL/g in SVI. The max. specific release phosphorus rate (SRPR), the max. specific uptake phosphorus rate (SUPR) and the phosphorus content of the MLSS (TP/SS) was 67.7 mg/(g x h), 43.2 mg/(g x h) and 6.5% respectively on the 437th day. On the 448th day the operation of the reactor was changed into A/A/O. The max. SRPR, the max. anoxic SUPR and the TP/SS of the denitrifying phosphate uptake granular sludge was 30 mg/(g x h), 27.9 mg/(g x h) and 6.3% respectively on the 653rd day. The two kinds of granular sludge had potential to carry out phosphorus removal.