Effects of Aeration Rates and Patterns on Shortcut Nitrification and Denitrification

The effects of aeration rates and aeration patterns on the oxidation of ammonia-nitrogen into nitrite were investigated. The influent high ammonia-nitrogen synthetic wastewater resembled to those of the catalytic process of the petrochemical refinery. The method involved the biological shortcut nitrification and denitrification lab-scale’s sequencing batch reactor (SBR) process based on intermittent aerations and aeration patterns. All the operations were carried out in a 20 L working volume SBR bioreactor, and the influent synthetic wastewater’s concentration was always 1000 mg/L ammonia-nitrogen NH4-N concentration at a C/N (carbon/nitrogen) ratio of 2.5:1. Effective shortcut nitrification to nitrite was registered at 1.1 mg-O2/L (i.e. 9 L-air/min) with 99.1% nitrification efficiency, 99.0% nitritation rate and 2.6 mg-NO3--N/L nitrate concentration. The best results with 99.3% nitrification efficiency were recorded when operating at 1.4 mg-O2/L (i.e. 12 L-air/min). According to these experiments, it results that the nitrite accumulation rate was related to aeration rate and cycle’s duration. However, at 1.7 mg-O2/L (i.e. 15 L-air/min), the system was limited by an increase in nitrate concentration with more than 5 mg/L which could be a point of reverse to conventional nitrification. The best total nitrogen (TN) removal was about 71.5%.

Effect of vacuum degree and aeration rate on sludge dewatering behavior with the aeration-vacuum method

Due to large-scale dredging operations, a large amount of sludge is inevitably produced. Large areas of land are occupied when the dredged sludge is discarded in the disposal site as waste material. The sludge dewatering with aeration-vacuum (SDAV) method is suit for treating the sludge with high water content and high clay content in the disposal site. The water in the sludge can be discharged out. The volume of the sludge can be reduced quickly, and the recycling of the land can be accelerated by this method. Most importantly, this technique is an efficient way to deal with clogging problems when pumping water from high water content, high clay content dredged sludge. Vacuum degree range tests, the aeration rate range tests, and the influencing factors of sludge dewatering behavior tests were conducted with a self-developed SDAV model test device. Sludge samples were taken from the South-to-North Water Diversion East Line Project in Huai’an White-Horse Lake disposal site, Jiangsu Province, China. The optimal range of vacuum degree and aeration rate were obtained through the test results, and the mechanisms for how the two factors work and how they affect the sludge dewatering behavior were analyzed. The suitable vacuum degree range in SDAV is below 50 kPa, and the suitable aeration rate is about 1.0 m3/h. The low-vacuum degree contributes to reduce the ad-sorption effect of micro-channels on soil particles in filter material and to maintain the arch structures. Aeration has the effects of expansion, disturbance, changing Reynolds number, and dynamic sieve separating. The pump quantity of water per meter of filter tube (m) has different change rules as the vacuum degree changes under different aeration rates. The reason is that the formed arch structures’ conformation and permeability differ greatly under different combined-conditions of vacuum degree and aeration rate. The optimal combined-condition for dewatering the sludge is 35 kPa with 1.0 m3/h.

Effect of aeration rate on composting of penicillin mycelial dreg

Pilot scale experiments with forced aeration were conducted to estimate effects of aeration rates on the performance of composting penicillin mycelial dreg using sewage sludge as inoculation. Three aeration rates of 0.15, 0.50 and 0.90 L/（min·kg） organic matter（OM） were examined. The principal physicochemical parameters were monitored during the 32 day composting period. Results showed that the higher aeration rate of 0.90 L/（min·kg） did not corresponded to a longer thermophilic duration and higher rates of OM degradation;but the lower aeration rate of 0.15 L/（min·kg） did induce an accumulation of NH＋4-N contents due to the inhibition of nitrification. On the other hand, aeration rate has little effect on degradation of penicillin. The results show that the longest phase of thermophilic temperatures ≥ 55°C, the maximum NO-3-N content and seed germination, and the minimum C/N ratio were obtained with 0.50 L/（min·kg） OM. Therefore, aeration rates of0.50 L/（min·kg） OM can be recommended for composting penicillin mycelial dreg.

Aerobic N_2O emission for activated sludge acclimated under different aeration rates in the multiple anoxic and aerobic process

Nitrous oxide（N_2O） is a potent greenhouse gas that can be emitted during biological nitrogen removal. N_2O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 m L/min sequencing batch reactor（SBRL） and 1200 m L/min（SBRH）.The nitrogen removal percentage was 89% in SBRLand 71% in SBRH, respectively. N_2O emission mainly occurred during the aerobic phase, and the N_2O emission factor was 10.1%in SBRLand 2.3% in SBRH, respectively. In all batch experiments, the N_2O emission potential was high in SBRLcompared with SBRH. In SBRL, with increasing aeration rates, the N_2O emission factor decreased during nitrification, while it increased during denitrification and simultaneous nitrification and denitrification（SND）. By contrast, in SBRHthe N_2O emission factor during nitrification, denitrification and SND was relatively low and changed little with increasing aeration rates. The microbial competition affected the N_2O emission during biological nitrogen removal.

Application of Submerged Ultrafiltration in Pretreatment of Flue Gas Desulfurization Wastewater

Nowadays,the zero liquid discharge of flue gas desulfurization(FGD)wastewater from coal-fired units has attracted the attention of all countries in the world.The pretreatment methods generally have the problems of high operation cost,small treatment capacity,and poor flexibility.However,the membrane method can avoid the above problems.In the current research,it has not been found that someone directly uses submerged ultrafiltration to pretreat FGD wastewater.Therefore,this paper innovatively proposed to directly use ceramic ultrafiltration membrane to treat FGD wastewater,which can ensure effluent quality and improve the flexibility of the pretreatment system.In this paper,the performance of submerged ultrafiltration membrane for the filtration of FGD wastewater from a power plant was studied to optimize the filtration performance and improve the effluent quality.The effects of operating parameters such as membrane permeate flux,aeration rate and filtration/backwashing time combination on the membrane performance were studied.The results showed that when the filtration/backwashing time combination was 15 min/30 s,with the increased in permeate flux from 55 L/(m2·h)to 100 L/(m2·h),the steady transmembrane pressure(TMP)increased from 39 kPa to 70 kPa,and the fouling rate increased significantly from 4.5 kPa/h to 7.3 kPa/h;When the aeration rate increased from 10 m3/(m2·h)to 30 m3/(m2·h),the membrane pollution was much reduced.Excessive aeration rate cannot further alleviate the membrane pollution,but also brought greater energy consumption;Increasing backwashing time can effectively inhibit the formation of gel layer on the surface of the membrane and prolong the initial stage of low-pressure operation;The rejection of suspended solids(SS)and turbidity of the equipment studied in this paper can reach more than 99%under various working conditions,which can satisfy the water quality requirements of the subsequent steps.The submerged ultrafiltration membrane was suitable for the pretreatment of FGD wastewater because it can ensure the quality of permeate under the premise of long-term operation.

Prediction of Dissolved Oxygen and Study of Engineered Nanoparticles to Improve Water Quality

The lack of fresh water is one of the greatest challenges of our time.Increasing population and arid regions due to the temperature change limit the use of clean water.In this paper,Streeter-Phelps equation was used to find the levels of DO(Dissolved Oxygen)and the oxygen deficit which are the main criteria for the water body quality.Reaeration constants and deoxygenation coefficients were used to find how the DO and BOD(Biological Oxygen Demand)of the water bodies converge to equilibrium.Some pollutants cannot be removed from water efficiently via traditional water treatment.EDTA derivatives,owing to their engineered chemical properties,are also studied to be the potential metal ion chelator for enhancement of water quality.These molecules were tested for their thermodynamic stabilities,reactivities,and polarizations,and these characteristics are found to be important factors in selecting the most suitable chelator for metal ion chelation which is used for water quality control.

Characteristics of night soil and leaf co-composting using aerobic static method

The main purpose of this work is to investigate the characteristics of night soil and leaf co-composting using aerobic static composting method. Three influencing factors, including proportion of night soil and leaf, aeration rate and aeration pattern, were investigated through the evolution of the principal physicochemical properties, i.e., temperature, oxygen consumption rate, organic matters, moisture content, carbon, nitrogen, carbon-to-nitrogen ratio and Germination index （GI）. It was found that the 3：1 （w：w） mixture of night soil and leaf was capable of achieving the highest composting temperature, longest retention time of high temperature （55℃）, and fastest organic matter degradation. The 0.14 m3. min-1. m-3 aeration rate was most beneficial to composting, and the mixture of night soil and leaf maintained the highest temperature for the longest duration and achieved the highest CO2 content and GI. The continuous aeration pattern during composting was superior to an intermittent aeration pattern, since the latter delayed the composting process.

Escherichia coli inactivation by pressurized CO_2 treatment methods at room temperature: Critical issues

This study aims to increase the inactivation efficiency of CO_2 against Escherichia coli under mild conditions to facilitate the application of pressurized CO_2 technology in water disinfection. Based on an aerating-cycling apparatus, three different treatment methods（continuous aeration, continuous reflux, and simultaneous aeration and reflux） were compared for the same temperature, pressure（0.3–0.7 MPa）, initial concentration, and exposure time（25 min）. The simultaneous aeration and reflux treatment（combined method） was shown to be the best method under optimum conditions, which were determined to be 0.7 MPa, room temperature, and an exposure time of 10 min. This treatment achieved 5.1-log reduction after 25 min of treatment at the pressure of 0.3 MPa and 5.73-log reduction after 10 min at 0.7 MPa. Log reductions of 4.4 and 5.0 occurred at the end of continuous aeration and continuous reflux treatments at 0.7 MPa, respectively.Scanning electron microscopy（SEM） images suggested that cells were ruptured after the simultaneous aeration and reflux treatment and the continuous reflux treatment. The increase of the solubilization rate of CO_2 due to intense hydraulic conditions led to a rapid inactivation effect. It was found that the reduction of intracellular p H caused by CO_2 led to a more lethal bactericidal effect.