There are many industrial minerals
used in wastewater treatment. Some are used as filtration aids,
such as perlite, bentonite, diatomite and silica sand, while
others, such as lime and magnesia, are used as chemical
When IM last
covered wastewater treatment in December 2009, a need for more
products in the market was identified as industrial development
was still relatively buoyant compared with today.
But the shape of many industrial
minerals end markets has changed significantly in the past
Construction has hit a lull as many
economies have slowed down. Supply has also been interrupted in
some parts of the world due to civil unrest. For example, the
Arab Spring temporarily affected delivery of minerals, such as
bentonite, out of Egypt.
The purpose of neutralisation is to
adjust the pH value to meet the requirements of the different
processing units in the wastewater treatment system.
Neutralisation may be used to treat
acid wastewaters containing metals. This method involves
increasing the pH of the acid waste by adding an alkaline
reagent to form a precipitate and then collecting the
precipitate. This way, the incoming solution is pH adjusted to
the optimum range for precipitating metals as hydroxides.
This process is conducted before
the main step of wastewater treatment, that is clarification
(or, decantation), to fulfil the overall wastewater treatment
The largest uptake on wastewater
neutralising products is from the chemical and manufacturing
industries. In these sectors, demand for products is still
strong, Gwyn Watkins, Lhoist UK Ltd sales and logistics
director, told IM.
Lhoists key wastewater
product is the Neutralac SLS45 (see p69). This is a
liquid-lime treatment for acidic effluents of all types.
Some sectors of the market
are in a deep recession, construction and steel
specifically, he said. I think the feeling is that
we are going forward to a pretty flat five years. People will
need to be creative in order to expand. Business will have to
For now, however, demand for
Lhoists neutralising product is still firm.
Demand is growing. We are
selling - our sales have increased by 1,000 fold since 2009. In
our product, we have seen substantial growth in this year. We
expect 30% more sales this year, and last year was up 80% on
the previous year, he said.
Demand is also high at US-based
Martin Marietta Magnesia Specialties, which produces a
neutralising agent made from magnesium hydroxide.
We continue to see increasing
demand for most of our product lines, including magnesium
hydroxide, Douglas Bopst, vice president of sales, told
Looking forward, the company agreed that economic growth
or contraction will influence demand for magnesium
|Martin Marietta Magnesia Specialties
Image: Michigan manufacturing facility
Most companies contacted by
IM did not specifically outline which was the
largest end market for its wastewater products, although it was
agreed that the chemical industry formed a large part of the
Its very difficult to
say what the largest segment is, Watkins told
Its very diverse. We
are used in a large part in the chemical industry, in water,
food manufacturing and in metal treatment, he added.
There is a split in the industry
between those who believe that magnesium hydroxide is the
better solution for neutralising wastewater and those that
believe lime with sodium hydroxide (caustic soda) is the more
The arguments centre around cost,
safety and supply security, and are summarised below.
US-based Premier Magnesia LLC said
that while caustic soda and lime are more commonly used in the
neutralisation process because they are usually the most
practical choice, magnesium hydroxide could be the safer
Technical grade magnesium
hydroxide suspensions are akin to pharmaceutical grade
Milk of Magnesia used to neutralise excess stomach
acid, Dr Mark Shand, Premier Magnesia director of
technical services, said in an article, Magnesium Hydroxide
- A Safer Alternative to Caustic Soda (Sodium Hydroxide),
on the company website.
They are therefore safe and
non-hazardous and will not cause chemical burns. Magnesium
hydroxide has found great use in treating industrial
metal-laden acidic wastewater, where, compared with caustic
soda or lime, will produce less sludge volume, and a filtercake
that de-waters more readily, he said.
Martin Marietta Magnesia
Specialties Bopst agreed that there were benefits to
using magnesium hydroxide.
The company produces a product
called FloMag, which it describes as a safe and cost-effective
method for alkalinity addition and pH adjustment of acidic
In a white paper produced for the
company titled The use of magnesium hydroxide slurry for
biological treatment of municipal and industrial
wastewater, Aileen Gibson and Michael Maniocha argue that
magnesium hydroxide slurry is much safer to handle than
caustic soda, and does not scale equipment like hydrated
These benefits combined make
magnesium hydroxide slurry superior to caustic soda and
hydrated lime when selling into the wastewater treatment
industry, the report said.
Municipal wastewater treatment plants that are currently
using caustic soda and hydrated lime to provide alkalinity
during nitrification would be good candidates for conversion to
magnesium hydroxide, the report concluded.
Unsurprisingly, Lhoist Group
believes its product is superior to a magnesium hydroxide
The problem is that when you
make slurry it doesnt dissolve it, like with calcium
hydroxide, Watkins said.
You have to keep it stirring
otherwise it will separate out. What we have done, by changing
the shape of the calcium hydroxide particle, is ensure it will
stay the same, which means we can put more material in this
way. Our material stays in suspension, you can put more in
there and keep it in suspension, he added.
Shand, in a second article on
Premier Magnesias website, Storage and Handling of
Magnesium Hydroxide Slurries, outlined the specifications
of handling slurry.
Some agitation is needed to
keep solids in suspension while the slurry is in storage,
he said. This can be done by a top-entering, pitch-blade
turbine or rake-type agitator. Agitator shaft speed will vary
depending on the impeller size and length of shaft.
Lhoist has refined its product
since 2009, Watkins added.
The milling process has
changed. [...] We have improved the processing of the lime
hydrate to give it greater stability, he said.
Demand for its products is growing,
the company said, which suggests that end users are also
switching to its products. This is because a lime-based
solution does not require as much intervention once the
solution is in place.
A lot of companies have
switched, and they found they can cut back on stirring and the
amount of effort that entails, Watkins said.
The lime used to make the product
is sourced in Buxton, UK, where the company is based. It is of
such high purity that it is exported to other parts of Europe
and to Asia.
A European directive was set out in
1991, which specifically dealt with wastewater treatment.
The Urban Waste Water Treatment
Directive of 1991 concerned the collection, treatment and
discharge of urban wastewater, and the treatment and discharge
of wastewater from certain industrial sectors throughout
It set dates for end users to put
in place a way to treat water discharge. These varied depending
on the population exposed.
The European Commission published
three report in 2004 on the implementation of the directive.
The reports noted that the wastewater treatment situation in
Europe was still very unsatisfactory and that none of the
deadlines had been met by all member countries.
The reports also revealed that
pollution parameters, such as nitrogen levels, remained high.
This was down to insufficient nutrient removal by wastewater
treatment plants, the reports said.
The directive represents the most
cost-intensive European legislation in the environmental
sector, according to the European Commission. The EU estimates
that the equivalent of 152bn ($195bn) was invested in
wastewater treatment from 1990 to 2010.
EU Reach (Registration, evaluation
and authorisation of chemicals) regulations set out further
rules on how to deal with wastewater.
Companies affected were all those
which import, manufacture, repackage, formulate, supply and use
water-treatment chemicals. It affects all water-treatment
areas, including industrial and municipal wastewater treatment;
industrial, commercial and consumer water supply treatment; and
water treatment at the point of use.
CLP, or CLP Regulation, is the new
European Regulation on classification, labelling and packaging
of chemical substances and mixtures.
CLP is mostly concerned with the
hazards of chemical substances and mixtures, and how to inform
others about them. There will be an obligation to apply CLP to
mixtures by 2015.
Reach was more a health and
safety issue, Watkins said. Theres an
understanding of the material, which is more in depth. So,
theres a lot of information that has to be
Reach meant that magnesium hydrate
and sulphate have to be registered by 31 May 2013.
Lime substances also have to be
registered. These incorporate calcium oxide, dihydroxide,
calcined dolomite, calcium magnesium, and lime (chemical)
hydraulic, according to the Industrial Minerals Association,
which has worked with the industry in preparation for the
various deadlines set out by Reach.
As well as REACH, Europe-based
wastewater treatment manufacturers faced more regulation when
the Industrial Emissions Directive came into force on 6 January
This directive not only affects
companies such as Lhoist, which calcine lime on site and
therefore use a lot of gas in order to do so, it also affects
companies which have any wastewater to treat.
When wastewaters from the
cleaning of waste gases are treated outside the waste
incineration plant or waste co-incineration plant at a
treatment plant intended only for the treatment of this sort of
wastewater, the emission limit values set out in Part 5 of
Annex VI shall be applied at the point where the wastewaters
leave the treatment plant, the directive states.
Where the wastewater from the
cleaning of waste gases is treated collectively with other
sources of wastewater, either on site or off site, the operator
shall make the appropriate mass balance calculations, using the
results of the measurements set out in point 2 of Part 6 of
Annex VI in order to determine the emission levels in the final
wastewater discharge that can be attributed to the wastewater
arising from the cleaning of waste gases, it
The industrial emissions
directive [...] will affect us, Watkins said. But
that is more in gasses than liquid effluent.
While there has been a big push in
regulation, there has also been an increase in information
available, as well as a pressure from shareholders to be seen
to be complying with environmental standards, Watkins said.
Its not like
theres been a big-step change, but theres no doubt
that other companies are finding more pressures. Theres a
pressure from environmental regulation and water. Theres
a pressure to reduce costs [É], people are aware that
regulations are being applied more tightly, he added.
Martin Marietta in the US is also
subject to to tighter regulations, Bopst told
Regulatory requirements on
wastewater treatment in the US continue to tighten, and will
continue to have the objective of improving the cleanliness of
wastewater prior to discharge, he said.
Both Lhoist and Martin Marietta
agreed there are cost pressures from their respective customer
There are always cost
pressures in every facet of manufacture, including the
treatment of wastewater, Bopst said.
Industrial companies look for
ways to use less water in their process, and better recycle the
wastewater they do generate, he added.
Meanwhile, an increase in energy
prices has affected costs at Lhoist, the company said.
Energy is the biggest impact
we have in manufacturing lime non-stop [...]. We have managed
our gas usage as well as we can, by using recirculation shaft
kilns, which make the best use of energy, for example, it
The company has to use gas to power
its process as it is the cleanest fuel. This means
that the company is more also exposed to the carbon emissions
trading scheme, which will be a further cost.
One of the benefits of our
magnesium hydroxide slurry products is that both economic and
technical improvements are available in certain processes to
help reduce effluent treatment costs, Bopst said.
Also, magnesium hydroxide has cost stability relative
to competitive products such as sodium hydroxide, he
Making the switch to magnesium hydroxide
Switching to magnesium hydroxide saw an annual saving of more
than $100,000 in chemical costs at a municipal wastewater
treatment plant in Kentucky, US, according to
The municipality used soda ash for
nearly 15 years to supplement alkalinity in the biological
treatment of wastewater.
The plant was attracted to
magnesium hydroxide because of its improved alkalinity and
because the pH levels could be controlled. This is important in
the state of Kentucky where an upper discharge limit of pH 9.0
cannot be exceeded.
There was also a concern about the
long-term availability of soda ash as well as the cost of water
spray to mitigate the toxic zone foam caused by soda ash. The
switch was made in 2007.
After initial tests, the facility
then switched to lime slurry in 2009, after a water treatment
consultant said it could save even more money (quoting a figure
of $370,000). But the city came to realise that the costs
associated with limes operational issues outweighed the
chemical cost savings, WaterWorld reported.
The citys treatment plant
experienced excessive scaling, which led to flow interruptions,
plugging of lines and pipe fittings, and equipment failures.
The plant also experienced a large increase in solids at the
belt filter presses, which required increased landfill
The plant reconverted to magnesium hydroxide in
Heavy metal and fluoride removal from wastewater in the metal
A leading global automotive
supplier in France uses the Henkel process to give the
different components in its heating, ventilation and
air-conditioning systems anticorrosion and hydrophobic
The wastewater generated by
this operation contains heavy metals and fluoride. The plant
used a combination of NaOH for the neutralisation and
CaCl2 for the precipitation of fluoride and heavy
metals to treat the effluents before discharging them into a
CaF2 and metal hydroxides were then removed by
flocculation and filtration.
However, this did not
always prove effective in meeting the maximum fluoride
concentration (15 mg/l) imposed by the local
Lhoist offered a new method
for treating the wastewater:
- Getting the pH at the
entry of the process to a value of 6.5 and maintaining it at
that level instead of having the former fluctuations which
ranged between 5 and 12;
- Increasing the pH
during the treatment phase from 8 to 9.5 for a better
precipitation of the fluoride; and
- Simplifying the process by using a single
reagent instead of a combination of NaOH and
Costs in other minerals used in wastewater treatment
In other minerals used in wastewater treatment, the costs are
Imerys, the world leader in
filtration minerals such as perlite and diatomite, said in
November that it will be increasing European and US prices for
perlite and diatomite products by between 4% and 8%, effective
1 January 2013.
Price increases are necessary
to achieve a sustainable product platform and meet customer
demand, the company said.
Perlite is used in
wastewater treatment in its expanded milled form. Expanded
perlite has rough edges and curved surfaces, which interlock to
form an effective filter bed that does not compact.
meanwhile, is mainly used in beverage and food production, but
it is also used in water filter applications. Diatomite has a
large pore and void
volume and, therefore, a high
degree of permeability. It is chemically inert, lightweight and
can retain up to 90% of its void space during compression.
The last Imerys price rise in
perlite and diatomite took place in January 2012. At that time,
the French company raised prices by between 3% and 5% for
The companys Celite plant in
Murat, France, meanwhile, applied an energy surcharge on all
its goods, charging 25.50/tonne for November 2012. Celite
is a brand of diatomaceous earth.
The charge was last applied in
August 2012 at a rate of 25.50/tonne ($31.29/tonne),
which was a drop of 10.20/tonne from surcharges applied
in May 2012.
Rising fuel and gas costs are the
main causes of the rising energy costs, Imerys said, and left
the company with no alternative but to implement [the
Freight, packaging and raw
materials have also impacted Imerys business
dramatically, the company added.
Freight is often what the bentonite
market points to as being an added cost pressure.
Bentonite is used
as a flocculent in the purification of wastewater, isolating
and removing oils, heavy metals and suspended solids. This is
by no means the largest market segment for bentonite (see
p40), but it is a growing sector for the mineral.
AMCOL International Corp., one of the worlds largest
producers of bentonite, has surface modified bentonite clay to
produce a filtration media that removed mercury from water,
rendering it soluble and non-toxic.
Lhoist is always seeking new areas to expand into, it said. As
well as being used in wastewater treatment, its Neutralac SLS45
product has been sprayed on asphalt to avoid cracking and also
used as a foot bath for cattle, Watkins said.