Process for treating ammonia nitrogen wastewater by gas-state membrane

Abstract

The invention relates to a process for treating ammonia nitrogen wastewater by a gas-state membrane. The process comprises the following steps: adopting a composite discolouring agent and a heavy metal catcher to pre-treat high-concentration ammonia nitrogen wastewater, feeding high-concentration ammonia nitrogen wastewater into an air stripping tower to perform ammonia nitrogen removal, introducing stripped ammonia gas into a hydrochloric acid absorption tower to generate ammonium chloride; mixing stripped wastewater with low-concentration ammonia nitrogen wastewater to obtain waste liquor, regulating the pH value of the waste liquor to be 10.5 or more, performing ultrafiltration, introducing ultra-filtered waste liquor and absorbing liquor into the gas-state membrane assembly, controlling flow speed andthe temperature, removing ammonia nitrogen to obtain an ammonia salt solution and waste liquor with ammonia nitrogen content lower than 10 mg/L; feeding the ammonia salt solution to the air stripping tower after regulating the pH value, passing through the hydrochloric acid absorption tower to obtain ammonium chloride. The process has an ammonia nitrogen removal rate higher than 99%; the treated waste liquor meets discharge standards. In a process, the gas-state membrane is good in stability, does not generate osmotic distillation of water; and a gas-state membrane process canbe continuously performed, so that industrial implementation is facilitated.

Description

technical field [0001] The invention belongs to the field of ammonia nitrogen wastewater treatment, and in particular relates to a process for treating ammonia nitrogen wastewater by using a gaseous membrane. Background technique [0002] In recent years, with the rapid development of petrochemical, coal chemical, fine chemical, fertilizer, pharmaceutical, metallurgy, electronics and other industries, the daily discharge of ammonia nitrogen wastewater has been increasing. Ammonia nitrogen in wastewater is an important substance for water eutrophication and environmental pollution, which affects water quality and human health, and also causes a huge waste of resources. Therefore, the country requires ammonia nitrogen-containing wastewater to be removed using ammonia nitrogen removal technology, and can only be discharged after reaching the "Comprehensive Wastewater Discharge Standard". [0003] At present, the most common ammonia nitrogen removal technologies include biologi...

AI Technical Summary

Problems solved by technology

[0005] However, in the gaseous membrane deamination process, not only ammonia molecules enter the absorption liquid through the membrane wall, but also water molecules enter the absorption liquid through the micropores on the membrane wall (associated osmotic distillation), resulting in rapid expansion of the absorption liquid volume, As a result, the absorption solution is diluted, and the higher the acid and salt concentration in the absorption solution, the more serious the osmotic distillation of water, so it is difficult to obtain the expected by-product, that is, a high-concentration ammonium salt solution

Chinese patent CN106186492A overcomes the accompanying osmotic distillation problem by keeping the temperature difference between the wastewater and the absorption liquid at 10-20°C, increasing the ammonia nitrogen concentration in the wastewater to 1000-10000mg / L, and adding electrolytes to the wastewater, but the temperature difference in this method Difficult to control, both sides quickly reach temperature balance, and high concentration of ammonia nitrogen affects the stability of gaseous membrane modules, resulting in easy pollution and shortened service life, which limits its popularization and application

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