Development of a dynamic water softening system – DSS

Для питьевого водоснабжения часто используются подземные источники воды с повышенным содержанием солей жесткости. Известные методы умягчения приводят к образованию значительного количества жидких и твердых отходов – минерализованных сточных вод или шламов, не подлежащих утилизации. Реагентное умягчение питьевой воды в осветлителях используется достаточно редко из-за трудности приготовления реагентов, поддержания необходимой и постоянной температуры воды, сложности установок и их обслуживания. С 1990-х годов получила довольно широкое применение в питьевом водоснабжении технология реагентного умягчения в интенсифицированных реакторах (вихревых и во взвешенном слое). Такие аппараты достаточно широко используются в Европе и США. В настоящее время АО «НПК «Медиана-Фильтр» проводит работы по созданию и исследованию такого типа реакторов. Они имеют высокую удельную производительность – 50–100 м3/(м2·ч) и существенно проще в обслуживании, чем осветлители. Производительность таких установок достигает тысяч кубометров в час. Главное их преимущество заключается в отсутствии жидких сбросов, получении отхода в твердом виде, который может быть утилизирован, а также практически 100%-ном выходе чистой воды. Underground water sources with a high concentration of hardness salts are often used for drinking water supply. The known methods of softening result in the formation of a significant amount of liquid and solid waste – saline wastewater or sludge that cannot be subject to utilization. Chemical softening of drinking water in clarifiers is rarely used due to the difficulty of preparing chemicals, maintaining the required and constant water temperature, to the complexity of installations and their maintenance. Since the 1990s, the technology of chemical softening in intensified reactors (vortex and in a blanket) has been widely used in drinking water supply. Such apparatuses have been widely used in Europe and the USA. Currently, Mediana-Filter Research and Production Company, JSC has been working on the development and study of this reactor type. They have a high specific capacity – 50–100 m3/(m2·h) and are much easier to maintain compared to clarifiers. The capacity of such equipment reaches thousands of cubic meters per hour. Their main advantage is the absence of liquid discharges, generation of solid waste, which can be subject to utilization, as well as an almost 100% yield of clean water.

Removal of Ca2+, Mg2+, Ba2+ and Sr2+ from shale gas flowback water from the Sichuan Basin in China by chemical softening under the guidance of OLI Stream Analyzer: precipitation behaviors and optimization study

The disposal of flowback water is recognized as a key issue for the sustainable shale gas development and discharge after reasonable treatment is considered as a feasible pathway. One of the challenges during treatment is the severe mineral scaling potential in reverse osmosis desalination, especially with high amounts of Ca2+, Mg2+, Ba2+ and Sr2+ in flowback water. In this study, precipitation behaviors of Ca2+, Mg2+, Ba2+ and Sr2+ during traditional chemical softening was evaluated so as to achieve optimal chemical dosage. Both jar tests and OLI Stream Analyzer simulation revealed that the main precipitates were CaCO3, SrCO3 and BaSO4 during Na2CO3 addition, and Ba2+ could not be removed efficiently by Na2CO3 unless a high dosage was applied since Ba2+ would react after the precipitation of Ca2+ and Sr2+. Reverse Osmosis System Analysis simulation indicated that Ba2+ was a concern because Ba2+ would form tenacious BaSO4 scale on the reverse osmosis membranes. Finally, the Na2SO4-NaOH-Na2CO3 process was proposed for chemical softening as it has a high removal efficiency and low chemical cost. Overall, this study presents an effective chemical softening method and OLI Stream Analyzer could serve as a reliable tool for the calculation, which would finally improve the design and operation of shale gas flowback water treatment.

The Chemical Softening Effect and Mechanism of Low Rank Coal Soaked in Alkaline Solution

In order to analyze the feasibility of chemical softening on low rank coals, bituminous coal was collected from the Qianqiu mine in Henan Province, China, and soaked in water and alkaline solution for different lengths of time. The complete stress-strain and acoustic emission (AE) experiments on the coal samples under uniaxial compression were tested on the RMT-150B Rock Mechanics Testing System and DS2 series AE signal analyzer. The results showed that the coal samples soaked in the water and alkaline solution present different characteristics in the deformation and failure process. As we increase the soaking time, the uniaxial compressive strength and deformation degree of the soaked coal samples in the alkaline solution and water decreased by 42.7% and 94.8% respectively. In the loading test, an AE signal is generated in all coal samples and the maximum ringing count rate and AE energy rate are present near the stress maximum for a short time. Moreover, the ringing count rate and AE energy rate have a good consistency with the stress-strain of the coal samples. The cumulative ringing count of the two groups soaked in water and alkaline solution decreased by 51% and 89% compared to the original coal sample. However, the decreased degree of the samples soaked in the alkaline solution is much higher than that of those soaked in water and the results showed that the alkaline solution has a better softening effect on the coal sample. With the increase of the alkaline solution concentration, the contact angle decreased from 112.5° to 41°. Through microscope and scanning electron microscopy (SEM) analysis of the soaked coal samples, we found that the pores and fissures increased, the structure of coal became loose, and the mechanical strength decreased sharply after soaking in the alkaline solution, thus achieving a chemical softening effect.