RST Environmental Solutions Ltd

RST Environmental Solutions Flocculation sheds aid in the removal of suspended solids in runoff from a variety of isolated and disturbed sites, i.e. construction sites, quarries and sub-divisions. As every site to be treated is different in size, rainfall, soil geology, we will custom make your flocculation shed.

Due to the unknown amount of coagulant that will be used you will receive a proposal for the site which will outline the costs involved. These include a monthly rental, chemical cost (rate per litre used) and a set fee for any extra one-off visits.

Flocculation.jpgIntroduction to the Flocculation process
Flocculation is the clumping together of particles to form a larger mass which in turn settles through the neutralisation of the electrical charge. The addition of a coagulant to water, followed by rapid mixing to disperse the coagulant, causes destabilisation of the colloidal suspension.

The subsequent reaction of these charged substances with charged colloids results in neutralisation of the electrical charges and permits contact between particles. This promotes formation and growth of flocculation or particle aggregations which are large enough to be removed by sedimentation.

Pond Design
When designing a chemically-dosed sedimentation pond you must allow for the following differences from standard ponds:

  • The design of a single inlet structure to allow for dosing into the main flow (flume/chute)
  • Some turbulence to be created at dose point to aid in mixing
  • Provision of a suitable flat area to site floc shed

Getting Started
First we determine the correct dose rate for your site by taking samples of runoff water to the laboratory for testing. We establish which coagulant will achieve the best result and what is the optimum dose rate to achieve good sedimentation control with minimal impact on the receiving environment. With information on the total runoff area of the site to be treated also in hand, we custom make the "shed" (header tank, displacement tank, chemical resevoir, dosing tray and slow start system) to suit your site.

The coagulant is proportionally-dosed by rain activation, so monitoring during the first few rain events is critical (we may need to adjust flow/dose rate by decreasing or increasing the catch tray accordingly). Once the system is running efficiently, we will provide regular monitoring and maintenance.

What We Require
A wood fibre mulch or straw mulch can be applied with a trackifier to hold the material in place. The trackifier forms a permeable barrier, so that water can pass through but it still holds the mulch intact. Damage to the mulch layer will mean spot failures may occur and some maintanence may be required.

  • Feedback of onsite information such as adverse weather conditions and any on site chemical usage likely to leach into the pond (e.g. lime stabilisation can change pond pH which in turn may affect the flocculation process).
  • Information with regards to changes in site runoff characteristics, which could be due to stripping site vegetation or revegetation etc.
  • Maintenance of an all weather track to allow servicing of a system etc.


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