The Production of Pure Spring Water by applying a Deferrization and Manganese Removal Installation
By The Softdrink Producer Winters Softdrink Industry B.V. In Maarheeze
For more than 200 years Winters Soft drinks Industry B.V., in the Maarheeze borough of Cranendonk, has used spring water for the production of various sorts of soft drinks. Winters Soft drinks Industry B.V. started at that time as the local beer brewery and is now one of the most modern soft drink producers in Europe.
The name Winters is not well-known by the consumer because the company’s attention is primarily on contract filling, this means filling disposable packaging for foodstuff concerns, retail chains and other commercial organisations.
High quality spring water is demanded for production because of the high quality of the soft drinks.
For the replacement of an old deferrization/ manganese removal installation, Winters Soft drink Industry B.V. has found a partner in Lubron Water Treatment B.V. in Oosterhout who will design and build a water treatment installation which will comply with the strict quality demands.
Along with the demands applied to quality, the system must also be reliable and simple to operate. This guarantees a large degree of operational safety.
- Reverse osmosis
- Water softening
- Electrode ionisation (EDI)
- Removal of manganese
- Cool water treatment
- Boiler water treatment
- Central heating water treatment
The spring water is found in Maarheeze at a depth of 80 metres and is of stable and good quality with an elevated concentration of iron, manganese and ammonium. The capacity and the quality of the purified spring water must comply at least with the European and Dutch standards for drinking water.
|Spring water after purification
The water specialists at Lubron Water treatment B.V. quickly arrived at the conclusion that the spring water should be purified by means of two filtering steps; deferrization and nitrification as the first step and removing the manganese as the second.
Three processes take place during the filtration of the spring water which are closely linked to each other, namely the deferrization, the removal of manganese and the nitrification.
The unaerated spring water is brought into intensive contact with oxygen for the deferrization. The deferrization can be split into several partial processes, namely; oxidation, hydrolysis, nucleation, precipitation forming and filtration.
Iron is present in spring water in the bivalued form and is oxidised to the trivalued form by the oxygen. This trivalued form will attract 6 water molecules to Fe(H2O)3+6. This will then hydrolyse via a large number of steps whereby an acid is formed. Eventually Fe(OH)3 is created via Fe(OH)2-5 and Fe(OH)2. (H2O)41- which is very difficult to dissolve and causes saturation. Precipitation will not occur immediately because an energy threshold must first be superseded. This is realised by choosing a suitable filter surface of sieved, sloping river sand. The first precipitation of ferrous-hydroxide will have a strong positive effect on further formation of precipitation. From this we can conclude that clean filter sand must be worn in for a period of time before the deferrization can start up properly.
The eventual quality of the deferrizated water depends on various parameters such as the pH (degree of acidity) of the water, the oxygen concentration, the buffer capacity, the flow speed, the choice of filter material, etc.
The deferrization is purely a chemical process and is also described as electro-kinetic absorption.
The complete deferrization process at Winters Soft drink Industry B.V. takes place during the first filter step.
The removal of manganese:
The removal of manganese can be a chemical process as well as a bacteriological one. We speak of a chemical process when there is a higher pH value and we speak of a bacteriological oxidisation when the pH value is lower.
Manganese appears in spring water in the bivalued form and the oxidisation occurs via the hydrate form of MnO2,Mn2O3 and Mn3O4 which are also difficult to dissolve.
The deferrization must be in a far stadium before the removal of manganese can begin. This is not a coincidence because the ferrous-hydroxide formed has a catalytic effect with regard to the oxidization of manganese. Also the Mn3O4, hausmannite, will work as a catalyst for the removal of the manganese (auto-catalyst).
The removal of the manganese is much more difficult than the deferrization and is influenced strongly by a higher pH value of the water. That is why use is made of a special pH-increasing filter layer during the second filtration step.
The ammonium NH4+ is converted into NO3- during nitrification, which is a micro-biological process.
At first the Nitrosomas bacteria converts the NH4+ into NH2- (nitrite) and then, aided by the Nitrobacter bacteria, this is converted again into nitrate whereby energy is released. The bacteria use the released energy for building-up their cell material (the biomass).
We can conclude from this that the amount of biomass increases continuously, but that the total amount made is relatively small.
The nitrification that takes place during the first filter step works well at the normal temperature of spring water of 10-11 ºC and a pH value of 6-9.
For the benefit of the oxidation, the unaerated spring water is brought into intensive contact with air in a special air blending arrangement. The raw water flows, under pressure and saturated with air/oxygen, into the closed first filter (i.e. the first filter tank) whereby the extra air bubbles present will be removed via an automatic ventilator.
The water passes the various filter layers at a speed of 9 m/h and is completely deferrizated and nitrificated.
The deferrizated, nitrificated water flows under pressure via a construction of filter plugs under the tank to the second filter in the series (i.e. the second filter tank) where the removal of the manganese takes place. If necessary the water can be aerated more after the first filter step.
The contamination remaining on the filter layers should be periodically removed – depending on the iron and/or manganese content in the water. This is done with air/ rinsing water. It is important that the rinsing is regulated carefully and periodically supervised after the implementation of the installation.
Both filter tanks are internally and externally coated, and equipped with a PLC control that enables fully-automatic control of the installations. The connections on the PVC pipelines are from stainless steel.