Flocculation

08/04/2015

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All too often, the water in your tank is cloudy even when the parameters governing the water balance are showing correct values. That is due to the presence of tiny suspended particles. The use of a flocculating agent is therefore essential to turn your water crystal clear again.

Why Flocculate?

Contaminants in pool waters can be categorised in keeping with the size of their particles or their consistency. The bigger a particle is, the easier it will be to filter. On the other hand, small particles will pass through the filter. Therefore, a filter with a low filtration rating will enable tiny particles to be filtered. Sand filters have a filtration rating between 20 and 50 µm. Therefore, particles smaller than 20µm will not be retained by this kind of filter. These particles are almost always organic matter, and when they are not trapped in the filter, they can slow down the disinfection process. It is therefore necessary to increase their size in order to trap them in the filter: this is what the flocculation process is all about. Flocculating agents destabilise the electric charges of small particles and pack them together. When they are gathered together, their size increases so that they can be retained in the filter.

[caption id="attachment_5551" align="aligncenter" width="300"]Simplified diagram of a sand filter with and without flocculating agent Simplified diagram of a sand filter with and without flocculating agent[/caption]

Simplified diagram of a sand filter with and without flocculating agent

Metal ions, colloidal pollutants and micro-organisms can therefore be effectively eliminated and removed from pool waters. The result is clear water which is more crystalline and which makes it easier to clean the pool and saves on disinfectant. Nb: It is important to know that some kinds of micro-organisms are even resistant to disinfectants. The only way to get rid of them is by combining flocculation and filtration. That is why a flocculating agent should be used in public pools which have sand filters.

How to Flocculate?

To achieve a high filtration quality associated with flocculation, particular parameters have to be observed.

Parameters Recommended values
pH 7.0 – 7.4
Calcium hardness (TH) > 50 mg/l CaCO3
Alkalinity (TAC) > 80 mg/l CaCO3

Values of recommended parameters when using flocculating agent

Manual use

For improved filtration, SCP has created a "flocculating pad". Placed in the skimmers or in the pre-filter of the pump, the Flocculating pad progressively releases its flocculating agents and helps to improve filtration while making the pool water clearer. Furthermore, as it acts progressively, the flocculating pad prevents the formation of suspended particles and removes any that are already present.

Flocculating pads

On account of its formula and its pre-dosed format, the Flocculating pad increases the filtration rating, makes the pool water clearer and improves disinfection. The flocculating pad is therefore ideal for all sand filters.

Directions for use

Use one pad per 25m3 and place it in the pre-filter of the pump or in the skimmer after the filter has been washed. Set the pH between 7.0 and 7.4. Repeat every 10 to 15 days. Nb.: flocculation is a process that can also be carried out on a regular basis owing to the flocculating powder product. All you have to do is set the pH between 7.0 and 7.4 and pour in 200g/10m3 of water to be treated directly in the tank skimmer.

Automated use (recommended for communal pools)

In view of the significant volume of the tanks and filtering components, you are recommended to use an automated installation in order to guarantee maximum comfort for all swimmers. This kind of system effectively tackles the considerable amount of particles left behind by swimmers. With this in mind, SCP has developed Flocculating Liquid; this concentrated product has been specially designed for use in communal pools. Due to its high concentration, Flocculating liquid guarantees crystal-clear waters at all times. Its packaging (in a 1-20 l can) promotes significant autonomy meaning that regular handling operations are not required.

Flocculating liquid

Easy to use due to its concentrated and pre-hydrolysed formula which has been specially designed for use in communal pools. The flocculating liquid is therefore ideal for all communal pools with sand filters.

Directions for use

The flocculating agent is continuously injected by metering pump after the pump pre-filter and in front of the sand filter, directly from the can. The permanent injection varies according to the frequency and environment of the tank.

Compliant tank 100 m3 400 m3 2500 m3
Recycling per day 1,400 m3/d 4,000 m3/d 20,000 m3/d
Indoor pool 1 l/d 3 l/d 7 l/d
Open-air pool 2 l/d 5 l/d 12 l/d

Quantity of pure liquid flocculating agent used per day of routine application. Nb 1: The injection point of the flocculating agent should be placed after the pre-filter of the pump and in front of the sand pump. On account of the speed of the flocculating process, you should make sure that the mixture between the flocculating agent and the water at the injection point is sufficient. This can be modified for instance by extending the diameter of the pipe at the injection point and by increasing the mixture time by at least 5 to 10 seconds before reaching the filter. Nb. 2: the flocculating agent should not be applied only in combination with a slow to average filtration speed and also with a particular height of the filter layer.

Cleaning the filter

Despite an excellent flocculation process, the water in your tank may continue to be cloudy. This is caused by your sand filter. It is therefore important to carefully maintain your filter. To guarantee that your filter operates in the best possible way:

  • Perform a backwash once every 10 to 15 days (in keeping with the internal filter pressure).
  • Perform regular and comprehensive cleaning/limescale removal operations (once every 1 or 2 months and with the tank open).

With that in mind, SCP recommends the product: filter cleaner. Filter cleaner: specially designed formulation for all filter components. Sand filter: elimination of scale deposits, rust, etc. and generally all deposits of a mineral origin present in the filter medium. Directions for use:

  • 1 litre for 75kg of sand for family pools, for "quick sand" filters.
  • 1 litre for 100kg of sand for communal pools, for "slow" filters.
  • Backwash the filter and then rinse.
  • Introduce the product upstream of the filter (skimmer, spout or pre-filter), start up the filter for a few seconds in the "drain rinsing" position to spread the product throughout the filter until the colouring appears in the indicator light.
  • Allow to act for at least twelve hours, or even overnight.
  • Backwash and thoroughly rinse the filter until the colouring has completely disappeared.

Nb: Although more restrictive, the best method, however, consists of pouring the product directly into the open filter on the sand, after taking the precaution of bringing the water level to the sand level and closing all valves.

Why change the sand of the filter?

The sand of the filter inevitably wears out. When it is new, the sand has grains whose size and outline are clearly defined. During its use and whenever a backwash operation is performed, the grains smooth out under the effect of the circulation of water and get smaller and smaller. Therefore, it is necessary to change the filter mass every 5 years approximately.

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