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Constructed wetlands (CWs) are generally used for wastewater treatment and removing nitrogen and phosphorus. However, the treatment efficiency of CWs is limited due to the poor performance of various substrates. To find appropriate substrates of CWs for micro-polluted water treatment, zeolite, quartz sand, bio-ceramsite, porous filter, and palygorskite self-assembled composite material (PSM) were used as filtering media to treat slightly polluted water with the aid of autotrophic denitrifying bacteria. PSM exhibited the most remarkable nitrogen and phosphorus removal performance among these substrates. The average removal efficiencies of ammonia nitrogen, total nitrogen, and total phosphorus of PSM were 66.4%, 58.1%, and 85%, respectively. First-order continuous stirred-tank reactor (first-order-CSTR) and Monod continuous stirred-tank reactor (Monod-CSTR) models were established to investigate the kinetic behavior of denitrification nitrogen removal processes using different substrates. Monod-CSTR model was proven to be an accurate model that could simulate nitrate nitrogen removal performance in vertical flow constructed wetland (VFCWs). Moreover, PSM demonstrated significant pollutant removal capacity with the kinetics coefficient of 2.0021 g/m2 d. Hence, PSM can be considered as a promising new type of substrate for micro-polluted wastewater treatment, and Monod-CSTR model can be employed to simulate denitrification processes.

Sichuan Basin in China is rich in shale gas resources and has great exploration and development capacity. It is the main area of shale gas exploration and production in China. The proved shale gas reserves discovered by Sinopec in Weirong area exceed 100 billion m3, and they play an important role in the development of shale gas in China. In Sichuan Basin, the use of traditional shale gas production methods such as multi-stage hydraulic fracturing is hampered by serious casing deformation. By December 2019, Sinopec performed hydraulic fracturing operations in 20 wells in this area, where casing deformation was encountered in 10 wells, resulting in an increase of up to 5.69% in the proportion of invalid fracture sections. In order to explain the mechanism of casing deformation during hydraulic fracturing, the geological structures of a shale gas production site in Sichuan Basin with frequent casing deformation were examined, and the geological reasons for this deformation were revealed. In addition, a geological model was established to calculate the influence of formation activation induced by fracturing fluid on the casing load, and formation activation during hydraulic fracturing was studied. The results reported in this paper are of great significance for optimizing hydraulic fracturing parameters and reducing the influence of formation activities on the casing of horizontal wells.