The major aim of wastewater management is to remove as much of the suspended solids as possible before the remaining water, called effluent, is discharged back to the environment.
Wastewater treatment is a process used to convert wastewater into an effluent (outflowing of water to a receiving body of water) that can be returned to the water cycle with minimal impact on the environment or directly reused. -wiki
1. Collection of Waste water
- All the flow-back waste water to be collected into pits at well sites once it flows from sub surface to surface.
- Transfer the collected water from distributed pits to the centralized treatment facility and discharge in Pit-1
2. Treatment of Waste water
- Allow enough residence time in Pit-1 till insoluble lighter impurities floats on liquid surface. While Liquid waste water is siphoned from bottom of Pit-1 to Pit-2.
- Aerator is used in Pit-2 to oxygenate the waste water and then sent to EC unit.
- Control and monitor the TSS value of waste water using EC unit.
3. Transfer of treated water to tank farm or treated water storage pit.
4. Pumping of waste water in disposal well.
The waste water management layout is shown below in Fig 1:
Waste Water Characteristics
- TDS (Chlorides) – Interference with formation.
- TSS – Down hole plugging.
- Metals (Iron, Calcium) – May form precipitate.
- pH – May form precipitate.
Waste Water Plant Setup
Block diagram of the Waste water plant is shown in Fig 2 and explained below:
- The waste water from Pit #2 is transferred to collection tank via a submersible pump to the De-gasser tank. HCL is dosed in the flow-stream if pH value>7.
- The Degasser system is designed to remove the H2S from the Effluent stream.
- After the Degasser, PAC is dosed at 1-2% concentration at inlet of the Intermediate tank. Whereas, at the outlet line Polymer is dosed at 7-8 ppm concentration.
- The chemically treated water is then transferred simultaneously to DAF1 and DAF2.
- The Primary Dissolved Air Floatation unit (DAF 1) provides for the mixing of dissolved air with particles in the effluent to encourage bubble-solid contact and flotation. This segment is designed to grease and suspended solids. The semi-sludge generated is then transferred to the Filter Press.
- Similarly the water fed to the Secondary DAF from Intermediate Tank is allowed to settle down and then generated sludge is moved to filter press.
- Then to extract any residual sludge, treated water is transferred from DAF1 and DAF2 to Tube Settler.
- Extracted sludge is moved to filter press and treated water is sent to Feed Tank and further fed to the tank farm or Pit #3 for storage and disposal purpose.
- Finally filter press is used to form solid sludge and drain out treated liquid with the help of filter cloths and compression pump. All the Solid waste generated is transferred to the designated landfill.
Plant is currently generating ~ 1600bpd of treated water by using Chemical Coagulation method. And ~1440 bpd of injection of treated water in the well.