Orica - MHL

Benefits of MHL for pH Control

Dosing Control
Irrespective of how much MHL is added, the maximum pH achievable is within the range of pH 9 - 9.5. This is in contrast to traditional alkalis which if added in gross excess can result in pH values between 12 and 14. Notably, pH 9 is the upper pH limit specified in many trade waste discharge agreements and is approaching the upper pH limit tolerable by many aerobic and anaerobic digester bacteria. This upper pH limit of 9.5, or buffer effect, achievable with MHL essentially eliminates the risk of high pH excursion allowing simplification of dosing control systems.

Scaling
Unlike calcium sulphate, magnesium sulphate is highly soluble. Therefore neutralisation of sulphate containing effluent with MHL will not result in voluminous sulphate sludges or pipe blockages due to sulphate scale formation often associated with lime dosing.

Salinity
By replacing sodium alkali for pH correction with MHL, the levels of sodium in treated effluent is minimised. Further the increased magnesium levels result in a reduction in the Sodium Absorption Ratio (SAR) of the treated effluent. If the effluent is destined for irrigation or tertiary treatment using wetland systems, the reduction in SAR can reduce the risk of soil degradation and subsequent loss in soil fertility. In addition MHL provides beneficial nutrients to plant and animal life.

Operator Safety
Magnesium hydroxide, the active agent in MHL is the major ingredient in many antacid formulations (milk of magnesia) and as such poses little health risk. Accordingly MHL is classified as a non dangerous and non hazardous alkali reagent. MHL can be stored and pumped in much the same way as liquid caustic soda eliminating solids handling issues associated with lime and soda ash.