A sustainable approach to dairy wastewater management — Magnesium Hydroxide

Calix Limited
Monday, 01 February, 2021



Throughout the dairy industry, there is a constant requirement to monitor and control wastewater and effluent before discharge from the plant for compliance. Treating dairy wastewater before it is released into water bodies is a complex process, with biological treatments preferred.

The wastewater discharged by dairy processors is highly saline, meaning the sodium content is usually relatively high. Too much salt can cause toxicity called “osmotion”. This causes plant tissues to dry out and can impair its ability to uptake adequate moisture. Salty effluent can be diluted with other wastewater streams upon discharge, but the high salinity can trigger penalties imposed by local water authorities.

After being asked by the local municipality to neutralise and control the pH swings from its wastewater, this dairy plant installed an equalisation basin. However, even after installing the new system, the operators still struggled to keep the pH under the compliance requirements, due to exceptionally challenging and fluctuating acidic conditions.

After consulting with the municipality, it was decided that an alkaline reagent would be needed to help control the acid spikes that resulted in the problematic low pH. Because the local municipality applies a portion of its final effluent to the land, the dairy plant was also required to limit the sodium load in its discharge, which restricted caustic soda.

To meet this commitment, the plant operators followed the municipality’s recommendation and chose Magnesium Hydroxide as the ideal alkaline reagent.

Magnesium Hydroxide (Mg(OH)2) has a higher neutralising value per pound than any other alkaline additive. This translates into a 40% reduction in chemical usage when compared with caustic soda. It is also significantly safer for operators to handle and more nutritive for the microorganisms being maintained, making it the most cost-effective option.

Magnesium Hydroxide was found to provide better pH and alkalinity control compared to NaOH (caustic soda), while also reducing sodium in the discharge, for better environmental and compliance outcomes.

Magnesium Hydroxide slurry is also more attractive to end-users because of its safe handling properties and buffering ability, which provides the added benefit of excellent pH control.

Magnesium Hydroxide buffers to a maximum pH of nine in most wastewater streams, making biomass-damaging pH excursions less likely. (Lime and caustic soda can easily reach a pH of 12 and 14, respectively.) This contributes to the system’s stability and optimises microorganism activity, as microorganisms don’t respond well to pH swings.

The plant managers were pleased to see the cost savings achieved by switching to Magnesium Hydroxide, an alkalinity supplement for biological wastewater treatment.

Magnesium Hydroxide eliminated the environmental issues associated with sodium levels in the discharge, which allowed the municipality to rehabilitate the fields upon which the discharged water was sprayed into healthy farmlands. It also allowed the dairy processor to efficiently prevent pH spikes in its wastewater discharge, and achieve time and cost savings with a safe and environmentally friendly solution.

For more information about the case study, click here.

ACTI-Mag — Calix’s Magnesium Hydroxide for wastewater treatment applications

ACTI-Mag is one of Calix’s solutions to key water-based environmental challenges.

When used in wastewater treatment, ACTI-Mag significantly reduces odour and improves the quality of water while having a real and meaningful impact on climate change.

ACTI-Mag is created in Calix’s proprietary flash calcination and hydration technology, which produces a very high surface area Magnesium Hydroxide. Calix technology is a reinvention of the kiln process, which can produce high purity, high surface area products that have high levels of reactivity. New materials produced by Calix technology are proving to have similar reactive properties to nano particles, without the safety concerns or high cost of production.

Calix technology also allows for the direct separation of CO2, allowing it to be used for CO2 reduction in traditionally CO2 intensive industries. Made with high surface area MgO (200m2/gm), Calix ACTI-Mag provides excellent neutralisation speed and produces less sludge, making it a much more stable product, which stays as a suspension longer compared to other Magnesium Hydroxide slurries.

Image credit: ©stock.adobe.com/au/Yakov

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