Primary settlement is the first major stage of the treatment process which is mainly to remove the bulk of the solids in the effluent before the Eco SAF treatment stage and usually consists of a primary tank. Other processes can be incorporated at the primary stage to improve the process, these can include a balance chamber to control the forward flow to the Eco-SAF module, manual or mechanical screening to assist in the removal of gross solids from the effluent, sand separation, clarifiers or separation systems to remove fats, oils and grease. The selection of these additional processes depends on the needs of each individual project.
The primary tank is used to remove solids from the effluent before it reaches the Eco-SAF stage. The Pollution Control range of primary tanks are designed and sized to achieve a good hydraulic retention time and ensure a sufficient settlement of the effluent., When the effluent enters the tank it is allowed to settle out due to the retention time, the heavier solids drop towards the base of the tank and the lighter solids float towards the top. Between these two layers is the liquid effluent which can be treated by the Eco-SAF module, the primary tank has a specially designed weir that only allows the liquid effluent to progress to the secondary stage of the process. The remaining solids and floating scum is removed from the tank periodically.
The balance chamber is used to control the forward flow of the effluent; it is sized to allow a certain amount of effluent to be stored in the chamber. Once this level is reached the effluent is pumped on to the next stage of the process, this allows the flow of effluent is regulated so that a specific retention time through the second stage can be achieved.
In most cases the effluent will contain gross solids that could damage or clog pumps and can cause inefficiencies further down the process by fouling the media in the Eco-SAF™. For this reason a manual rag screen is installed at the inlet end of the primary tank, this is usually a bar screen designed to stop larger solids entering the tank and can be raked clean as and when required. In some cases where there is a large amount of solids within the effluent a mechanical screening process can be put in place, the specification of the type of screening system is depends on effluent being treated
Clarifiers / Sand Seperation
In some cases where there are large amounts of silt or sand within the effluent a lamella clarifier or sand separator can be installed. The abrasive nature of silt and sand can cause problems in the later stages of the treatment process, build up causing obstructions in the pipes and channels within the system and can cause damage to pumps Removal of silt and sand will keep the process working efficiently.
Oils, Fats and Grease
In some commercial wastewater treatment applications the effluent will contain oil, fat or grease, these can cause problems in the process so a separation system needs to be installed before the primary treatment stage.