Effect of alkalinity on nitrite accumulation in treatment of coal chemical industry wastewater using moving bed biofilm reactor

Nitrogen removal via nitrite （the nitrite pathway） is more suitable for carbon-limited industrial wastewater. Partial nitrification to nitrite is the primary step to achieve nitrogen removal via nitrite. The effect of alkalinity on nitrite accumulation in a continuous process was investigated by progressively increasing the alkalinity dosage ratio （amount of alkalinity to ammonia ratio, mol/mol）. There is a close relationship among alkalinity, pH and the state of matter present in aqueous solution. When alkalinity was insufficient （compared to the theoretical alkalinity amount）, ammonia removal efficiency increased first and then decreased at each alkalinity dosage ratio, with an abrupt removal efficiency peak. Generally, ammonia removal efficiency rose with increasing alkalinity dosage ratio. Ammonia removal efficiency reached to 88% from 23% when alkalinity addition was sufficient. Nitrite accumulation could be achieved by inhibiting nitrite oxidizing bacteria （NOB） by free ammonia （FA） in the early period and free nitrous acid in the later period of nitrification when alkalinity was not adequate. Only FA worked to inhibit the activity of NOB when alkalinity addition was sufficient.

Forward osmosis coupled with lime-soda ash softening for volume minimization of reverse osmosis concentrate and CaCO_(3) recovery: A case study on the coal chemical industry

Reverse osmosis(RO)is frequently used for water reclamation from treated wastewater or desalination plants.The RO concentrate(ROC)produced from the coal chemical industry(CCI)generally contains refractory organic pollutants and extremely high-concentration inorganic salts with a dissolved solids content of more than 20 g/L contributed by inorganic ions,such as Na^(+),Ca^(2+),Mg^(2+),Cl^(−),and SO_(4)^(2−).To address this issue,in this study,we focused on coupling forward osmosis(FO)with chemical softening(FO-CS)for the volume minimization of CCI ROC and the recovery of valuable resources in the form of CaCO_(3).In the case of the real raw CCI ROC,softening treatment by lime-soda ash was shown to effectively remove Ca^(2+)/Ba^(2+)(>98.5%)and Mg^(2+)/Sr^(2+)/Si(>80%),as well as significantly mitigate membrane scaling during FO.The softened ROC and raw ROC corresponded to a maximum water recovery of 86%and 54%,respectively.During cyclic FO tests(4×10 h),a 27%decline in the water flux was observed for raw ROC,whereas only 4%was observed for softened ROC.The cleaning efficiency using EDTA was also found to be considerably higher for softened ROC(88.5%)than that for raw ROC(49.0%).In addition,CaCO3(92.2%purity)was recovered from the softening sludge with an average yield of 5.6 kg/m^(3) treated ROC.This study provides a proof-of-concept demonstration of the FO-CS coupling process for ROC volume minimization and valuable resources recovery,which makes the treatment of CCI ROC more efficient and more economical.

Reviews of clean coal conversion technology in China:Situations & challenges

It is important to develop the advanced coal to chemicals industry(ACCI)against a backdrop of coal-based energy structures,excessive imported oil and natural gas,and strict environmental constraints in China.In this study,the technology and industry of China’s ACCI are reviewed to explain the effect of using coal to replace oil and natural gas,and the corresponding resource and environmental burdens that this will create.Development trends in technology and industry are also proposed to explore future scenarios.The review shows that although excellent progress has been made on an industrial scale,demonstrative level,and in terms of technology and equipment,the lack of strategic understanding,severe external constraints,partly underdeveloped technologies,and weak foundations must be immediately addressed.Therefore,it is necessary to clarify the importance that the ACCI has on the energy revolution and energy system.Based on technological innovation,a variety of external factors should be considered as a whole with emphasis on filling the knowledge gap of theoretical foundations and industry standards to support high-quality development for ACCI.

Capability of phenol-degrading biofilm

The degradation rate of phenol-degrading biofilm was studied.The biofilm of the biofilm was a kind of phenol-degrading bacteria.The bacteria was separated from coal chemical industry wastewater.The carbon source adopted four kinds of phenols,including phenol,methyl phenol,2-methyl phenol and resorcinol.Stenotrophomonas maltophilia K279a was gained.Twelve ratio of artificial phenol mixture was designed.The degradation rate of the twelve groups was all 99.9% in 16 h.The degradation rate from high to low was phenol,resorcinol,methyl phenol,2-methyl phenol.Phenol improved the degradation of the other phenols.The coal chemical wastewater contained 980 mg/L COD and 805 mg/L phenol.The degradation rate of COD and phenol was 70% and 77%,respectively.The domesticated biofilm (D) and the biofilm without domestication (WD) respectively used 45 h and 56 h.The results showed that the biofilm can be applied to the aerobic treatment process with high proportion of total phenol.

Hybrid peroxi-coagulation/ozonation process for highly efficient removal of organic contaminants

Aromatic compounds such as phenols presented widely in coal chemical industry wastewater(CCW)render the treatment facing great challenge due to their biorefractory characteristics and potential risks to the environment and human health.Ozone-based advanced oxidation processes show promising for these pollutants removal,but the mineralization via ozonation alone is unsatisfactory and not cost-effective.Herein,a hybrid peroxi-coagulation/ozonation process(denoted as PCO)was developed using sacrificial iron plate as an anode and carbon black modified carbon felt as cathode in the presence of ozonation.An enhanced phenol removal of∼100%within 20 min and phenol mineralization of∼80%within 60 min were achieved with a low energy consumption of 0.35 kWh/g TOC.In this novel process,synergistic effect between ozonation and peroxi-coagulation was observed,and beside O_(3) direct oxidation,peroxone played a dominant role for phenol removal.In the PCO process,the hydrolyzed Fe species enhanced the generation of reactive oxygen species(ROS),while•OH was dominantly responsible for pollutant degradation.This process also illustrated high resistance to high ionic strength and better performance for TOC removal in real wastewater when compared with ozonation and peroxi-coagulation process.Therefore,this process is more cost-effective,being very promising for CCW treatment.