Phosphate production

In 2007, Slibverwerking Noord-Brabant (SNB) concluded a five-year cooperation contract with phosphor producer Thermphos for the supply of phosphate-rich sludge ash. Thermphos uses this sludge ash in its production process. The contract is a growth contract. SNB currently supplies 6000 tons of sludge ash per year, and this must be 18,000 in 2013. Thermphos pays SNB for the delivery of sludge ash, which means that SNB generates a small profit with this transaction. More important is the social benefit. This is how SNB succeeds in recycling the phosphate production of 1.4 million people.

Not all ash is suitable

Only iron-poor sludge is suitable for use in the Thermphos production process. However, the water boards frequently use iron salt in water treatment plants, which increase the level of iron in the sludge. Replacing this with aluminium salts is a solution. The disadvantage is the higher cost price of aluminium. However, it is possible to purchase aluminium at a lower price, as a remnant. Some water boards already do this. Slibverwerking Noord-Brabant (SNB) is also prepared to use the profit from the sale of iron-poor sludge ash in order to reduce the extra costs.

A second alternative to cleaning with iron salts is biological cleaning. An increasing number of water boards are converting to this when modernising or replacing their waste water treatment plants.

All in all, there are enough ways to produce iron-poor sludge. Currently, 20% of the sludge that is supplied to SNB is iron-poor. SNB is striving to increase this percentage to 50% within 5 years, which will mean that more phosphate can be recovered!