Improving the sustainability of water treatment

Fertiliser that contains nitrogen (N), phosphorous (P) and potassium (K) is known as NPK fertiliser and it’s one of the most valuable resources in the world when it comes to agricultural production. The world’s farmers have relied on phosphorous to grow food for centuries but phosphate reserves are dwindling and experts believe that peak phosphate, which is the catastrophic decline in output of phosphate, could have a bigger impact on food supplies than even climate change.

While phosphate occurs naturally in numerous sources, including manure, farmers have relied on phosphate rock for fertiliser since the mid-1900s.

Phosphate mine deposits are expected to be depleted within a few centuries, creating a predicament for the agriculture industry, requiring it to manage the amount of phosphate that makes it into fresh water while preserving phosphate supplies for use as fertiliser.

“In the mid-1800s, food shortages due to farmland nutrient depletion became a major problem. But, thanks to native Peruvians, NPK fertiliser came to the rescue and became one of the most valuable resources in the world.”

Calix business development manager, Michael Wheatland.

A DOUBLE-EDGED SWORD

Phosphate mining has made phosphate both plentiful and cheap in the past, which meant that thousands of tonnes were dropped on farmland every year.

This resulted in massive amounts of phosphate in wastewater and runoff from farms, which washes downriver and results in algal blooms. This can be disastrous as the algae die off and decompose, dropping oxygen levels to a point where fish and other aquatic life die in massive numbers.

The intensity of harmful algal blooms has increased over the past three decades, creating a worrying situation for many waterways. It can even potentially threaten drinking water, as was feared during the New South Wales bushfire emergency in late 2019* (*source: https://www.waterquality.gov.au/issues/bushfires).

Modern regulation already limits the amount of soluble phosphate that can enter rivers. This is usually managed by locking phosphate up in insoluble salts that end up at the bottom of the ocean, never to return. While it safely neutralises phosphate in rivers, this approach also means that the phosphate can’t be reused.

RECOVERING PHOSPHATE THROUGH WASTEWATER MANAGEMENT

Although it isn’t possible to create or synthesise phosphorus, it is possible to recover useable phosphorus from waste streams, including urban and industrial wastewater.

Sewage treatment plants can remove biological phosphorous to create a sludge that is high in phosphorous. Adding magnesium to the waste can help make and extract struvite, which is a phosphorous-rich material.

By capturing phosphorous in a biologically-available form within wastewater sludge, it can be composted and recycled as fertiliser, preserving nutrients in the land to ensure farming remains efficient for many more generations. This approach recycles phosphate back into the environment safely. Importantly, it guarantees the ongoing availability of this essential fertiliser.

While many organisations have tried and failed to create a costeffective technology to recover phosphate from wastewater, Calix has succeeded. Calix ACTI-Mag makes it possible to rapidly capture phosphate within the solid waste stream while removing the need for other harsh chemicals and the associated additional pH adjustment required.

REMOVING HARSH CHEMICALS FROM OUR WATERWAYS

ACTI-Mag is one of Calix’s flagship solutions to key water-based environmental challenges. When used in wastewater treatment, ACTI-Mag significantly boosts the conversion of organic waste into biogas, which can then be used to offset carbon-intensive energy production methods. It helps reduce odour and improve the quality of water while having a real and meaningful impact on climate change.

ACTI-Mag is created in Calix’s proprietary and unique 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.

Calix is also able to offer better service, reliability and performance to its customers because it controls the entire production process from mining of raw materials, processing and production. Calix owns and operates a mine in South Australia as well as production, testing facilities and manufacturing plants. The ability to hydrate our high surface area MgO in our patented, close-to customer facilities creates multiple benefits for our customers and local communities.

As a concentrated, stabilised suspension of magnesium hydroxide, ACTI-Mag has a higher neutralising value per dry kilogram when compared with caustic and lime, and is significantly safer than other traditional alkalis. It’s also a very cost-competitive option for hydrogen sulphide gas control in sewers and industrial waste treatment, which means it can help reduce unpleasant odours. It can also efficiently remove phosphorous and nitrogen from wastewater. This makes it the ideal solution for sustainable wastewater treatment.

MANAGING SALINITY TO IMPROVE THE QUALITY OF OUR SOILS

Sodium degrades the quality of soil, making it harder to grow healthy plants. It interferes with water’s ability to infiltrate the soil and seedlings’ ability to break through the surface. Farmers using water to irrigate their fields may inadvertently be adding excess sodium through the water source.

Many food manufacturing facilities use sodium hydroxide (*caustic soda” or “caustic”) to “clean in place” or flush their systems between food processing runs. This results in large amounts of wastewater with very high sodium levels requiring treatment before discharge.

Replacing caustic with ACTI-Mag, a natural mineral product, significantly lowers the sodium content in wastewater. This has an exceptionally positive impact on wastewater facilities and treatment plants downstream from the food factory.

The role of wastewater treatment in a more sustainable world

Michael Wheatland explains how to improve the sustainability of wastewater treatment using our product ACTI-Mag.

Improving sustainability of wastewater treatment

At Calix, we make a point of highlighting the challenges we want to solve. Phil Hogdson, CEO at Calix Limited, explains how to improve sustainability of wastewater treatment using our product ACTI-Mag.

Michael Wheatland, Calix business development manager said:

“With growing concern about the impact of industry and agriculture on Australia’s greenhouse gas emissions and the environment in general, biogas is swiftly emerging as the most attractive, affordable, and logical waste management solution available”.

Audrey Barucchi, Calix marketing manager said:

“Calix ACTI-Mag helps make an anaerobic biogas plant work much more efficiently, which reduces groundwater pollution, generates potentially re-usable industrial water, and also delivers a financial return on investment through sustainable power production”.

WASTEWATER CAN BE USED AS A SOURCE OF GREEN ENERGY

Traditional wastewater treatment plants aren’t necessarily optimised for the production of biogas from wastewater sludge. Biogas is created through anaerobic digestion, which requires the material to have the right pH levels so bacteria can break down the microorganisms in the wastewater stream. During this process, methane and carbon dioxide are created.

If the pH gets too low, significant amounts of hydrogen sulphide or “rotten egg gas” is released to the air, creating unbearable and toxic levels of contamination evidenced by a strong odour. When too much hydrogen sulphide is created, it can reduce the lifespan of the plant’s equipment because it becomes corrosive when it’s converted into sulphuric acid. Adding an alkali reduces production of hydrogen sulphide and maintains optimum bacterial growth conditions for anaerobic digestion.

Anaerobic treatment with biogas production is also a realistic solution for industrial sites and farms with concentrated wastewater management issues aiming to work sustainability philosophies into their wastewater management strategies. Treating wastewater with anaerobic processes to produce biogas energy can significantly reduce pollution, and help industries recycle water and cut costs that would otherwise go towards electricity and energy demands. Increasingly, industrial sites are investing in on-site anaerobic cogeneration plants to treat wastewater.

For example, a rendering plant that processes four million kilograms of animal waste per week was consuming more than $130,000 worth of electricity per month, the equivalent of burning 24,000 tonnes of black coal per year. Before working with Calix, the plant sourced half of its energy from a coal-powered generator and the other half from biogas.

Using ACTI-Mag to improve its biogas production helped the plant save more than $1.5 million in energy costs.

Calix has also worked with a South-West Victorian piggery to reduce hydrogen sulphide from pig waste biogas and to improve biogas production. Working with Calix, this piggery increased biogas volume by 20 per cent and power generation by 23.5 per cent. It decreased the average daily effluent soluble phosphate levels by almost 40 per cent and hydrogen sulphide by 70 per cent, significantly reducing the unpleasant odour.

Importantly, the piggery was able to achieve an increase in earnings of $68,000 per year from increased power generation due to the improved treatment of its wastewater.

Biogas is a viable alternative to traditional waste management approaches. It’s a clean, renewable energy that’s created from materials that would otherwise simply be wasted. It can reduce the greenhouse gas emissions of energy by over 20 times and prevents methane from escaping, directly into the atmosphere. Creating energy through biogas is considered carbon neutral, so it’s a genuine solution to excess emissions.