In the sewage treatment, the Mogden formula is a pricing strategy used to estimate the difficulty in treating industrial wastewater. It is named after Mogden Sewage Treatment Works.[1]
The Mogden formula calculates cost as a combination (empirical coefficients) of volume, strength in terms of normal treatment oxidation demand and the suspended solids proportion.[1] Applicable to the whole works, it also approximates the cost for tested industrial waste water that may, if treatable, be lawfully sent to a regular sewage works.[1] [2] [3] [4]
The Mogden formula is:
where:
= charge per volume of effluent (£/m3)
= reception and conveyance charge [£/m<sup>3</sup>]
= primary treatment (volumetric) charge [£/m<sup>3</sup>]
= additional volume charge for biological treatment [£/m<sup>3</sup>]
= treatment and disposal charge where effluent goes to sea outfall [£/m<sup>3</sup>]
= biological oxidation of settled sewage charge [£/m<sup>3</sup>]
= chemical oxygen demand (COD) of effluent after one hour of quiescent settlements at pH 7 [mg/litre]
= chemical oxygen demand (COD) of effluent after one hour of quiescent settlement [mg/litre]
= treatment and disposal of primary sewage sludge charge [£/m<sup>3</sup> or £/kg]
= total suspended solids of effluent at pH 7 [mg/litre]
= total suspended solids of effluent [mg/litre]
Thus the less biologically friendly the effluent (see wastewater quality indicators including pH), and more solid-laden, the higher the charge should be for treating the lawful effluent.[5]