Implementing a safe & cost effective alkali dosing solution

The irrigation of winery effluent onto woodlots is a common practice in Australian wineries. This waste stream is typically acidic, particularly during the vintage processing period, requiring alkali dosing before discharge.

The widespread use of caustic (sodium hydroxide) or potassium caustic (potassium hydroxide) for Clean-in-Place (CIP) systems within wineries, contributes a significant salt load to the effluent stream. This means neither are good choices for winery effluent pH correction.

To avoid the addition of salinity, the winery was using direct injection of anhydrous (gaseous) ammonia at their Buronga Winery.

However, this requires the management of a pressurised gas that is flammable, toxic, causes severe burning to eyes, skin & the respiratory tract and is also potentially hazardous to aquatic life.

The winery was not comfortable with this and were looking for an environmentally friendly alternative.

The winery readily agreed to a trial to start dosing ACTI-Mag during the 2020 Vintage (from March to late May 2020).

ACTI-Mag is a highly reactive slurry of magnesium hydroxide Mg(OH)2. ACTI-Mag is produced by Calix – using its uniquely high surface area magnesium oxide (MgO) as a 60% solids water-based slurry. The magnesium hydroxide solids in the slurry have a low solubility and high surface area allowing it to flow easily.

ACTI-Mag also provides more CaCO3 equivalent alkalinity, on an equal weight basis when compared to caustic soda, which lowers chemical consumption. With a pH of around 10.3 compared to a pH of 14 for 50% caustic soda (NaOH), ACTI-Mag provides greater than 60% more alkalinity than caustic soda.

This lower pH also means ACTI-Mag can be handled safely. It is non-hazardous and non-corrosive, with minimal personal protective equipment (PPE) required. Magnesium hydroxide, also known as ‘milk of magnesia’, is a common component of antacids, which further highlights the safety of the product.

On the contrary, anhydrous ammonia is a gas which has to be dissolved to become a useful alkali. The ammonia gas must be contained, as any leak is toxic and corrosive. It is usually sparged into a recirculation line to dissolve it. This can cause a lot of vibration and noise as it violently
reacts and dissolves.

They were very happy with the performance of ACTI-Mag for pH correction and felt far more comfortable with handling a safe alkali.