Study on the characteristics of gas field mercury-containing waste-water

Author of the article:YANG Yang, CAO Liang, ZHAO Qiong, HE Hua

Author's Workplace：CPECC Southwest Company, Chengdu, Sichuan, 610041, China

Key Words：Gas field waste-water; Mercury-containing waste-water; Water quality characteristics; Mercury forms

Abstract：With their distinctive characteristics, different mercury-containing waste-water treatment technologies are applicable for different water quality and mercury forms. Analysis of the water quality characteristics, total mercury concentration and mercury form is of great importance in the selection of the process for the removal of mercury from gas field waste-water. The results of a study on the effluent water quality of a mercury-containing natural gas treatment plant show that waste-water from the mercury-containing gas field is an acidic, highly chlorinated, mineralised and concentrated organic effluent, which is highly corrosive and prone to scaling; all kinds of mercury forms are present in the waste-water, with a small percentage of non-dissolved mercury and over 97% dissolved mercury. Organic mercury accounts for a small proportion of the dissolved mercury while the remaining proportion is inorganic mercury, with divalent mercury accounting for over 99%. In addition, the dissolved mercury exists mainly as a complex in high chloride ion environment, and the mercury-chlorine complex is highly stable. In order to achieve effective mercury removal, the mercury-containing waste-water treatment process should be selected with due consideration to the destabilisation of mercury complexes and a thorough analysis on the total mercury concentration and the presence of mercury forms in the water should be carried out.