In the process of geothermal tailwater reinjection of sandstone, the problem of plugging has been seriously restricting the continuous development of geothermal reinjection for many years, and the problems of plugging are complex and changeable. The plugging in the process of reinjection can be divided into physical plugging, chemical plugging, microbial plugging and gas plugging. Given these four types of blocking, according to the mechanism characteristics of the blocking caused by them, this paper puts forward corresponding blocking prevention measures and solves the current blocking problems by filtering, adding a scale inhibitor, intermittent reinjection, adding chlorine dioxide and regular lifting. In addition, the existing reinjection process and the equipment flow are relatively simple and cannot achieve the goal of efficient reinjection. Therefore, a complete set of reinjection processes is designed to ensure the efficient reinjection of sandstone geothermal tailwater.

Wastewater from the textile industry contains high concentrations of pollutants, so the wastewater must be treated before it is discharged. In addition, the reuse of treated wastewater should be considered from an environmental point of view, as large volumes of wastewater are produced. Since textile wastewater mainly contains dyestuffs, it must be treated effectively using environmentally friendly technologies. Membrane processes are widely used in textile wastewater treatment as they have distinct advantages over conventional wastewater treatment methods. This study reports the pilot-scale manufacturing and characterization of three different NF membranes. Three different types of membranes were fabricated. The fabricated membranes were compared through characterization by surface properties, chemical structure and morphology. Membranes were tested for pure water flux. Then the synthetic wastewater (SWW) was tested for flux and rejection. Lastly, the textile wastewater was tested. The textile wastewater flux of pure piperazine (PIP), 60% S-DADPS and 0.04% halloysite nanotubes (HNTs) were 22.42, 79.58 and 40.06 L m-2 h-1. It has been proven that the 60% s-DADPS membrane provides up to four times improvement in wastewater flux and simultaneously. In addition, NF membranes produced using HNT and sDADPS on a pilot scale have brought innovation to the literature with the good results obtained.

An invaluable utilization approach for industrial wastes is to employ them as effective adsorbents for environmental pollutants. This study aimed to investigate the phosphorus (P) adsorption behavior of coal wastes and zeolite in three forms of pristine powder (CP and ZP), nanoparticles (CNP and ZNP), and Fe (III)-modified nanoparticles (MCNP and MZNP). The adsorbents were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) analyses. The effects of pH, initial P concentration, and contact time were studied under batch mode. Results showed an optimum pH range of 2-6 for the P adsorption process. The pseudo-second-order kinetic model and the Langmuir isotherm described the P adsorption data well. The P adsorption capacity of the studied adsorbents was enhanced after modifications. However, the coal-based modified adsorbents represented higher P adsorption performances rather than the zeolite ones. The maximum P adsorption capacity (Qmax) values were obtained as 0.36, 3.23, and 30.48 mg g-1 for CP, CNP, and MCNP, and 0.80, 2.84, and 6.99 mg g-1 for ZP, ZNP, and MZNP, respectively. The surface complexation, ligand exchange, and electrostatic attraction processes were identified as the main P adsorption mechanisms by the studied adsorbents.

Efficient dewatering of sludge is necessary for its cost-effective transportation and final disposal. However, the common method of using polyferric sulfate (PFS) and polyacrylamide (PAM) requires a large amount of dosage and produces high iron ion content in the filtrate. This study examined a solution of applying polyamine (PA) coupled with inorganic coagulant PFS. The results demonstrated that using PFS + PA together could achieve the same or similar filtering rates as using PFS + PAM. The capillary suction time (CST) of PFS + PA (89.0 s) was equivalent to that of PFS (75.1 s) and better than that of PA (117.1 s) and raw sludge (RS, 403.8 s). Compared with PFS + PAM, the combination of PFS and PA efficiently removed Fe ions and chemical oxygen demand (COD) in sludge water content, with Fe ions in the sludge filtrate reduced by 97.8% and COD reduced by 78.9%, respectively. By analyzing the basic physicochemical properties of the sludge system, including the synergistic effect of coagulation and flocculation, sludge hydrolysis and flocculation, it indicated that PA + PFS could reduce bound water. These results demonstrated that combining PFS and PA to improve sludge dewatering performance is more beneficial than utilizing a coagulant or flocculant alone, even PFS + PAM.

A calcined CaMgAl-layered double hydroxide nanocomposite, CaMgAl-LDH (CCMA-0.83-600), was prepared by introducing Mg on the basis of CaAl-LDHs for the removal of phosphate from wastewater. The structure of the as-synthesized CCMA-0.83-600 was confirmed by XRD and SEM analyses. Parameters affecting the adsorption process of phosphate adsorbed by CCMA-0.83-600 were thoroughly explored, such as initial pH, adsorbent dosage and co-existing anions. The adsorption kinetic study suggested that the adsorption process accorded with the pseudo-second-order kinetic model and the adsorption rate was controlled by both the liquid film diffusion and intra-particle diffusion. The adsorption isotherm study indicated the adsorption process followed by the Langmuir isotherm model. Thermodynamic analysis suggested that the adsorption of phosphate was spontaneous and exothermic. The obtained results indicated that CCMA-0.83-600 is a suitable candidate for the removal of phosphate from wastewater.

Methanol has a significant effect on the performance of the completely autotrophic nitrogen removal over the nitrite (CANON) process. In this research, the effect of low-concentration methanol on the functional microorganisms and nitrogen removal and recovery in the CANON system is investigated. The result shows that the anaerobic ammonium-oxidizing bacteria (AnAOB) was suppressed with low-concentration methanol addition, and the phylum Planctomycetes was hidden. The genus Candidatus Brocadia was restrained, and the relative abundances reduced from 25.5 to 15.0% in the upper biofilm and from 20.3 to 14.3% in the bottom biofilm, respectively. However, low-concentration methanol promoted the nitrifying oxidizing bacteria (NOB) activity. This phenomenon reduced the average ammonium nitrogen removal rate from 95.0 to 70.7%, and the average total nitrogen removal rate decreased from 81.3 to 43.6%, respectively. The results demonstrated that the low-concentration methanol as an organic carbon matter harmed the CANON process. Fortunately, the CANON system had an excellent self-healing ability when the methanol was stopped, with the average ammonium nitrogen removal rate and total nitrogen removal rate returning to 95.5 and 80.9%, respectively. This research supplies a reference for practical engineering design and application by improving the understanding of the effects of low-concentration methanol on CANON process performance.

Thorium, as an important radioactive element, is widely present in nature, and its accompanying environmental pollution is also serious. Extracellular polymeric substances (EPS) are commonly found on the surface of microbial bodies and have strong adsorption capacity for metal ions. In this study, four methods were used to extract EPS from indigenous bacteria of rare earth tailings and to determine the best extraction method. The extracted EPS was applied to treat Th4+, and the changes in functional groups and composition of EPS were investigated. The results showed that the ultrasonic method was more efficient than other methods. The best removal efficiency was observed at pH 3.5, Th4+ concentration of 20 mg/L, and EPS dosage of 30 mL at 25 °C. After 9 h, the adsorption process reached equilibrium with a maximum removal efficiency of 75.93% and a maximum theoretical adsorption capacity of 25.96 mg/g. The Th4+ removal process was consistent with the Langmuir and Freundlich adsorption isotherms and the kinetic data were consistent with the pseudo-second-order kinetic model, which is mainly based on chemisorption. Amide I and amide II of proteins, C-H from aliphatic, as well as O-H and C = O from carboxylic acid play important roles in the adsorption process.

Recently, increasing attention has been paid to antibiotic resistance in stormwater runoff. However, there is no available literature about the control of antibiotic resistant bacteria (ARB) through 365 nm ultraviolet light-emitting diode (UVA/LED). In this study, batch experiments were conducted to investigate ARB inactivation kinetics, effects of light intensity and water matrix (including suspended solid (SS) concentration, initial pH and bacteria concentration), and potential transmission risks after UVA/LED irradiation. Results showed that ARB inactivation efficiencies reached 6.31 log reduction at 8 mW/cm2 (86 J/cm2) of UVA/LED for 180 min. ARB inactivation efficiencies increased with the increase of light intensity, and showed a linear relationship. ARB inactivation decreased with increasing SS levels, and the largest inactivation efficiencies was 3.56 log reduction at 50 mg/L of SS. Initial pH had slight effect on ARB inactivation through UVA/LED irradiation. A low initial bacteria concentration (105 CFU/mL) was not necessarily associated with good ARB inactivation (3.59 log reduction). After UVA/LED irradiation, ARB was hardly detected during 12 hr of dark repair, and the transfer frequency of kanamycin resistance gene was increased to 5.43 × 10-4. These suggested that the application of UVA/LED to inactivate ARB in stormwater runoff was feasible and desirable in this study.

A composite catalyst nZVI/Co/N-CNT was prepared by loading nano-zero-valent iron-cobalt bimetals on porous materials (N-CNT) by a liquid-phase reduction method. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and the X-ray electron spectroscopy (XPS) characterization method were used to characterize and analyze the structure of the prepared samples. The effects of different factors on the removal of levofloxacin (LOF) by the nZVI/Co/N-CNT activated persulfate (PMS) system were compared. The results show that the removal rate of LOF can reach 98.14% when the LOF concentration is 20 mg/L, the iron-cobalt molar ratio is 5:1, the dosage of nZVI/Co/N-CNT is 0.3 g·L-1, and the dosage of PMS is 0.2 g·L-1 and pH = 7. Free radical quenching experiments showed that SO4-· and ·OH coexisted during the reaction, and ·OH was the main active species, and the possible removal mechanism of LOF was speculated.

The inherent periodic structure of montmorillonite limits the adsorption capacity of its endogenous active units such as Si-O tetrahedron and Al-O octahedron for pollutants. The high-intensity ultrasound method was used to release these active units and the layer-by-layer assembly was adopted to prepare carbon@chitosan@montmorillointe microsphere adsorbent (C@CS@Mt) to give full play to the adsorption capacity of montmorillonite. The montmorillonite nanosheet exhibited good hole-making ability, resulting in high surface area, pore volume and pore diameter of microspheres. Benefitting from the release of active sites in Si-O tetrahedron and Al-O octahedron of montmorillonite nanosheets, the adsorption capacity of C@CS@Mt was significantly improved. The maximum adsorption capacities of Pb2+ and methylene blue (MB)reached 884.19 mg·g-1 and 326.21 mg·g-1, respectively. The simultaneous adsorption experiments indicated that the occupation of active sites by Pb2+ caused the observeddecrease of MB adsorption capacity. The theoretical calculations indicated that Pb was preferentially adsorbed by active adsorption units due to strong electron donating ability in comparison to MB. As an active unit, Si-O tetrahedron exhibited stronger adsorption capacity for cationic dyes than Al-O octahedron due to both the large electronegativity and lower adsorption binding energy.