Client: New power plant

Temporary sewage treatment plant for a new power station

  • Designed to treat wastewater from a workforce population equivalent of 800pe with no option to connect to the mains sewer network
  • New Gas turbine power station constructed at Carrington-Manchester by Duro Felguera and GEC Alstom– Build time approx. four years
  • Servicing and De-Sludging provided by Pollution Control.
  • Above ground installation that reduced civil cost and installation time scale
  • Permanent Eco-SAF system (65pe) also supplied for when the Power station was operational

Project Description

The Carrington STP is of the packaged type plant design and is based on our high performance modular Eco-SAF biological system comprising of:

  • Inlet pump chamber & grease/oil/fat (FOG) Separator
  • Primary settlement c/w Manual bar screen
  • Hydraulic flow control
  • Up-flow Bioreactor based on Submerged Aerated Filter (SAF) technology  Final clarification in a Lamella type Clarifier
  • UV Filtration
Population Equivalent (PE) 490 Flow / 800 BOD
Maximum BOD 48kg/d
Mean Hydraulic loading 88m3/d
Design flow 1.2l/s

The Carrington sewage treatment plant is to treat the construction site commercial wastewater to the effluent standard quality as follows:

Parameter Unit Discharge standard Compliance
BOD (5 day settled) mg/l 30 95%
BOD Kg/d 4.5 Maximum
S/S mg/l 35 95%
Ammonia as N mg/l 10 95%

Preliminary Treatment:

Comprising of the following elements:

  • Buried grease Separator situated at the canteen facility
  • Inlet pump station c/w Duty/Assist set back vortex impellor submersible pumps
  • Manual rake screen

Primary Treatment:

Primary Settlement/Flow Balancing Tank – Where heavy solids are allowed to settle into the sump of the primary tank as sludge. The sludge is removed periodically along with the lighter floating solids including any oils and grease. The tank is designed to BS 6297 2007 to ensure relevant surface area and rise rates are achieved. A scum board and weir is fitted to allow forward flow of only the decanted liquor. The module also has a flow balancing compartment which combined with the unique flow control system in the Eco-SAF provides equalisation of the incoming flow. This helps to prevent shock loading and provides a stable environment and control of the biomass in the bioreactor cells.

Secondary Treatment:

The Eco-SAF module – the essential biological stage where bacterial microorganisms are cultivated and actively consume the suspended organic material found in the decanted liquid from the primary process. The aerated cells are equipped with a fine-bubble aeration system distributing the oxygen that is required to maintain a healthy and stable population of heterotrophic bacteria. Oxygen is supplied to the air diffuser system by side channel Blowers c/w integral inverters that require minimum maintenance.

The module is a series of aerated cells and anoxic zones along with a De-Nitrification cell for enhanced ammonia removal. The aerated and De-Nitrification cells are also furnished with fully submerged bio-film growth media to ensure that the microorganisms have a substantial area for growth and a stable environment. Full floor coverage with the aeration diffusers ensures there is maximum oxygen transfer and there are no ‘unaerated’ dead zones as in circular tank designs.

Tertiary Treatment:

Final Settlement – Lamella clarifier. Any remaining solids (Humus) are settled out of the biologically treated effluent with the aid of a Lamella pack and returned upstream as enriched activated sludge (RAS) to be absorbed in fresh wastewater. The Lamella pack increases the active area and therefore improves the settling ability of the sludge within a small footprint.

Ultra Violet Disinfection – As additional tertiary treatment a UV system was installed to further treat faecal coliforms.

The Eco-SAF system was selected for the following reasons:

  • Predictable performance
  • Lower operation and maintenance costs
  • No interruption to the process whilst servicing the aeration system
  • Modular design with the addition of a De-Nitrification cell
  • Better whole life cost
  • Easy installation with minimum excavation required
  • Life expectancy of over 30 years with minimum maintenance
  • No internal moving parts
  • Easy to de-sludge
  • Manufactured to Quality Management System ISO 9001

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