Insight into microbial adaptability in continuous flow anaerobic ammonium oxidation process for low-strength sewage treatment.

Organic matter concentration is a critical factor influencing the adaptability of anaerobic ammonium oxidation (anammox) bacteria to low-strength sewage treatment. To address this challenge and achieve stable anammox activity, a micro-aeration partial nitrification-anammox process was developed for continuous-flow municipal sewage treatment. Under limited ammonium conditions, the effective utilization of organics in denitrification promoted the stable accumulation of nitrite and enhanced anammox activity. This, in turn, led to enhanced nitrogen removal efficiency, reaching approximately 87.7%. During the start-up phase, the protein content of extracellular polymeric substances (EPS) increased. This enhanced EPS intensified the inhibitory effect of denitrifying bacteria (DNB) on nitrite-oxidizing bacteria through competition for nitrite, thereby facilitating the proliferation of anammox bacteria (AnAOB). Additionally, several types of DNB capable of utilizing slowly biodegradable organics contributed to the adaptability of AnAOB. These findings provide valuable insights for ensuring efficient anammox performance and robust nitrogen removal in the treatment of low-strength sewage.

Study on the energy evolution mechanism of coal and rock with impact tendency under different strain rates.

To explore the strain rate effect of deformation and failure of impact prone coal rock, uniaxial compression tests and triaxial compression tests with different strain rates were carried out. The mechanical properties and impact tendency of impact-prone coal rock were studied, and the energy evolution law and pre-peak energy self-promotion-inhibition mechanism of impact-prone coal rock were obtained. The results show that with the increase of strain rate, the peak strength of coal rock under uniaxial compression decreases gradually, and the peak strength of coal rock under triaxial compression increases first and then decreases, and the impact tendency of coal rock increases first and then decreases. The energy evolution of coal rock under uniaxial compression is mainly divided into four stages: initial energy damage, energy hardening, energy softening and failure. With the increase of strain rate, the total energy and elasticity at the peak point of coal rock under uniaxial compression decrease gradually, and the total energy, elastic energy and dissipation energy at the peak point under triaxial compression increase first and then decrease. The elastic energy promotion coefficient of impact-prone coal rock is much larger than the inhibition coefficient, and the increase of strain rate will promote the generation of elastic energy inside coal rock. The research results can provide reference for the prevention and early warning of dynamic disasters of coal and rock mass with impact tendency.

Macroscopic and Mesoscopic Deterioration Behaviors of Concrete under the Coupling Effect of Chlorine Salt Erosion and Freezing-Thawing Cycle.

The aim of this study was to reveal the macroscopic and mesoscopic deterioration behaviors of concrete under the coupling effect of chlorine salt erosion and the freezing-thawing cycle. The rapid freezing-thawing test was carried out in a 5% chlorine salt environment. The macroscopic characteristics of concrete were analyzed by testing the mass, the relative dynamic modulus of elasticity, and the compressive strength of concrete under different freezing-thawing cycles. Using CT scanning technology and three-dimensional reconstruction technology, the pore structure, CT value, and surface deviation of concrete before and after freezing-thawing were analyzed. Based on the changes of solid volume, pore volume, and solid CT value of concrete, the calculation method of relative CT value was proposed, and the damage model was established with relative CT value as the damage variable. The results demonstrate that the mass loss rate decreases in the beginning and then increases in the process of chlorine salt erosion and freezing-thawing, and the smaller the concrete size, the greater the mass loss rate. The relative dynamic modulus of elasticity decreases gradually, slowly at the initial stage and then at a faster rate, and the compressive strength loss rate increases gradually. The pore quantity, porosity, and volume loss rate of concrete increase in a fluctuating manner, whereas the relative CT value decreases. The comprehensive analysis shows that the chlorine salt frost resistance of concrete is negatively related to the water-cement ratio when the freezing-thawing cycle is fixed. The damage model could better reflect the freezing-thawing damage degree of concrete with different water cement ratios, and the damage evolution process is well described by the Weibull function.