Water borne mineral opportunities

Published: Sunday, 22 November 2009

Belgium’s Lhoist Group explains how increasing industrial development and environmental regulation is opening new opportunities for wastewater treatment products such as its new Neutralac® SLS45

A world of ever-increasing urban development means that related industrial activity is constantly expanding. Different industrial processes produce different types of waste, all of which must be collected and treated before they are reintroduced into the environment. One of the most serious worldwide industrial challenges is how to minimise waste production, promote the reuse of water and find efficient solutions for treating waste and wastewater.

Lhoist Group, the lime and dolime producer, has recognised this need and consequently provides new and innovative treatments. The company supplies over 1,000 wastewater treatment customers and has been providing them with reagents.

A closer examination of the wastewater market shows a general trend towards increased regulation, as well as a drive to decrease effluent stream treatment cost per cubic metre. In addition to these continuous wastewater effluent streams, there are many other major projects aimed at rehabilitating existing sites which are contaminated by vast amounts of wastewater. Lhoist is actively involved in both these aspects of wastewater treatment.

Rehabilitating acidified open-pit lakes in east Germany
using lime-spreading boats. Courtesy Lhoist

Two examples of contaminated sites for which Lhoist is working on is the treating of acidic wastewaters from uranium ore mining operations in the Czech Republic, and rehabilitating acidified open-pit lakes in east Germany using innovative lime-spreading boats.

As far as continuous industrial effluents are concerned, the challenge is to provide higher quality reagents which can improve the efficiency of wastewater treatment. This means that the quality of the treated wastewater should not only be higher than with existing solutions, but should also cost less. Lhoist has developed Neutralac¨ SLS45 to meet these requirements.

Municipal waste treatment is a major growing market
for minerals. Courtesy Lhoist Group

Neutralac® SLS45

Neutralac® SLS45 was first launched in Germany by Lhoist’s sister company Rheinkalk in 2006. It was then produced in south France by Balthazard & Cotte in 2008, and Lhoist UK has recently started production in Buxton, north England. Through these three plants, Lhoist serves customers in western Europe.

The company explained: “Neutralac® SLS45 is safer to use than many alternative alkalines because it is neither toxic nor corrosive, and owing to its stable price, neutralisation costs can be planned sustainably.”

Lhoist officially opens its Buxton, UK Neutralac plan.
Courtesy Lhoist group

“Its solid content also means it has high neutralisation potential. It reacts quickly with no overdosing, which reduces reagent costs. Neutralac¨ SLS45 is ready to use and as it is free flowing, it is easy to handle. It can be delivered in bulk or in IBCs and because it retains its liquid qualities over time and is low settling, it is easy to re-suspend.

“Neutralac® SLS45 also offers logistical savings because a higher neutralisation equivalent can be transported for less. This reduces the number of deliveries needed and thus minimises vehicle traffic to the site,” it added.

Demand for the new product has seen a steady rise over the past few years.

Milk of lime: Neutralac up close. Courtesy Lhoist Group

Origins of the product

Lhoist started by identifying the advantages of existing alkalines and compared them with all the benefits of lime. The company then developed proprietary technologies and tailored a calcium hydroxide suspension. This possesses three properties which were previously difficult to combine; high reactivity, high concentration and low viscosity.

Neutralac® SLS45 reacts quickly which gives it an optimised reagent facility for acid neutralisation and pH control. Its high solids content of 45% means that it is more cost-effective than traditional lime slurry. Furthermore, it is almost as fluid as water, making it easier to handle than conventional products. Neutralac® SLS45 is also particularly stable as it will remain in suspension for a long time, requiring very little agitation and minimal handling.

As well as its neutralisation potential, Neutralac® SLS45 has also been used in heavy metal precipitation, a property welcomed by the metal plating industry. Operators in industrial and municipal wastewater treatment are exploring the possibility of replacing a combination of calcium based products, for example CaCl2, with other liquid alkalines such as NaOH, with a single reagent which can perform both Ca2+ and OH- functions. As well as removing sulphates and phosphates, it is also efficient in treating fluorides contained in hazardous effluents.

Neutralac® SLS45 is also becoming more popular for use in anaerobic biological digesters. Its buffering action stabilises the reactor pH that maximises bacterial development and increases the efficiency of the digester.

The product now has a wider use finding applications in the automotive, recycling, food and the pulp and paper industries. This allows users to comply more effectively with existing regulations and permits.

Precipitation of heavy metals is a core problem for
industrial waste water. Courtesy Lhoist Group

More minerals

The growth in wastewater treatment is opening up a number of opportunities for suppliers of bentonite, diatomite, magnesia, perlite, lime, silica sand and garnet.

Sodium bentonite’s absorption qualities make it a suitable candidate for treatment of affluent streams, waste ponds, and municipal sewage. About 26% or 1.3m. tonnes of bentonite is used for its absorption capability, but only a fraction of this, 3-5%, is for wastewater applications.

Diatomite and perlite tend be applied as a filtration media rather than a direct additive, and by volume, are two of the most widely consumed minerals in wastewater neutralisation.

Likewise silica sand is used as a packing in filters while garnet’s high specific gravity makes it desirable as a filter media in conjunction with the afore mentioned minerals. Around 15% of garnet is consumed in water treatment applications.

Magnesia has found an increasing use in this industry for its alkali properties, it many applications it is used as a substitute for lime or caustic soda.

Lime based products are some of the most cost effective methods in wastewater treatment, particularly in neutralising acidic waters and dissolving solids. It is particularly effective when applied in slurry form.

Contributor: Lhoist Group is a Belgium based lime and dolime producer which manufacturers products for a number of applications including wastewater, agriculture, chemicals and food industries.

Neutralac® SLS45 at a glance

Product name: Neutralac® SLS45
Product: a lime based alkali reagent

Application areas:

  • Neutralisation of acidic waste water
  • Precipitation of heavy metals
  • Improved heavy metals removal
  • Reduced use of costly flocculating agents
  • Post conditioning and hygienisation for sludges
  • Increasing sludge dewatering performance
  • Reduction of sludge quantities and associated costs
  • Prevention of floating sludge
  • Deodorisation of organic sludges and sewage
  • pH-value adjustment
  • Increasing the buffering capacity of the effluent

Application methods:
Preferred method direct dosing via pumps
Alternative method on site dilution prior to application


  • Transport in closed containers
  • In certified vehicles according to transport regulation for milk of lime up to 27 tonnes
  • Also available in partial deliveries or 1 m³ containers (IBC) by approved Rheinkalk distributors

Storage requirements:

  • May not be stored or transported in aluminium containers
  • In suitable storage tanks with safety arrangements
  • Requires re-suspension (mixing) before use to ensure product homogeneity
  • The ideal silo capacity is optimised via consumption and freight costs analysis

Safety data sheet: Calcium hydroxide in suspension/ milk of lime

Chemical analysis: Ca(OH)2 600 g/l
Physical analysis:

  • Solids content approx. 45 % w/w
  • Viscosity (Brookfield) approx. 400 mPa*s
  • Kiwa reactivity (90% dissolution) < 5 s
  • Density approx. 1,35 kg/l

Application scenarios

Electroplating waste

Problem: Precipitation of heavy metals

Industrial waste water purification
Problem: Precipitation of heavy metals, emulsion decomposition and neutralisation

Food industry
Problem: Deodorising, emulsion separation and neutralising wastewater

Municipal wastewater treatment
Problem: Clouding during final clarification, formation of floating sludge, development of filamentous bacteria, increase in sludge volume index (SVI)