Wastewater Treatment Activated Sludge Process – Basic Guide

Quite often in wastewater treatment, problems arise where basic checks and balances have been overlooked or not acted upon.

This basic guide for the operation, management and monitoring of the activated sludge process addresses fundamental issues which can mitigate against problems arising or assist in their resolution – saving time and money.

Mass Balances

  • It is good practice to carry out ongoing mass balances on water, wastewater and wastewater solids handling.
  • Such exercises should be devised to suit the particular characteristics and requirements of a given operation.
  • Where other materials (e.g. solvents, metals, specific toxic organic and inorganic substances) have the potential to adversely affect the operation of the wastewater treatment plant, they should also be tracked using mass balance techniques. 

Water Balance

  • Minimisation of water use is desirable in any industrial facility to conserve water resources, for cost minimisation, for effective process operation and for wastewater volume reduction. A typical water balance for a production facility might be as follows.

(Water In) = (Water Out) + (Water Consumption) + (Water Losses)

  • In order to keep a record of the water balance, all inputs and outputs should be metered. 
  • If the inputs and outputs do not correspond, there must be some unidentified water uses or losses (e.g. leaks).

Wastewater Balance

  • It is critical for the successful operation of a wastewater treatment plant to have accurate information concerning the wastewater volume being handled.
  • A simple water balance around the plant should be recorded daily.
  • A typical balance might be as follows.

(Influent) + (Water added) = (Effluent) + (Water in sludge)

Wastewater Solids Balance

  • The majority of wastewater treatment plants in Ireland utilise the activated sludge process. 
  • To satisfactorily manage this process it is necessary to continually monitor suspended solids (S.S., MLSS, MLSS, RAS, WAS).  
  • The objective of the materials balance is to determine the amount of new biomass that is created. 
  • This information is needed in order to establish a record of the Sludge Age – a very important plant monitoring parameter.
  • Where problems arise which are outside the competence of on-site personnel to solve, expert outside assistance should be promptly sought.

For more information please contact ECOS Environmental Consultants Limited at 061 633644/info@ecos.ie.