Aerated Lagoon Design Methods
An Evaluation
Based on Ontario Field Data
ALLAN R. TOWNSHEND, Engineer
SABRI UNSAL, Engineer
Division of Sanitary Engineering
BORIS  I.  BOYKO, Engineer
Division  of Research
Ontario Water Resources Commission
Toronto, Ontario
INTRODUCTION
Ontario became aware of aerated lagoons in April 1960 with the publication of
a paper by D. J. O'Connor and W. W. Eckenfelder, Jr., (1). The authors presented a
rational approach to the design of aerobic-anaerobic lagoons which were supplied additional oxygen by artificial means. A BOD5 material balance was used to derive the
BOD5 removal or efficiency equation:
E _ 100 Kt
1 +Kt
The first aerated lagoon built in Ontario, at Sandwich West, now the City of
Windsor, in 1965, was designed on this basis. As will be shown, the installation resulted in a complete-mix aerobic system. The other mechanical aerator installations
constructed to date in Ontario were also designed on this basis which has treatment
efficiency related to detention time and an overall removal rate constant K per day.
ONTARIO INSTALLATIONS AND DESIGN CRITERIA
There are presently 14 aerated lagoon systems in the Province with another 10
approved proposals underway. Three basic types of aeration equipment have been
used. They are mechanical surface aerators, both fixed and floating, perforated
tubing diffused air, and aeration gun diffused air. Of the 14 in operation, two are
complete mix aerobic, nine are aerobic-anaerobic, and three are combined basin (extended aeration and aerobic-anaerobic). The complete mix lagoons are without return
sludge facilities.
The basic design features of the two complete mix aerated lagoons at the City
of Windsor and the Town of Durham are shown in Table I. Typical design criteria of
aerobic-anaerobic lagoons represented by the Township of King Skyline Farms
Limited and the Township of North Grimsby installations are given in Table II.
COMPARATIVE CAPITAL COSTS
The construction costs of these lagoons have been compared with the design
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