Association ratings and determination of effluent quality
class
The percentage abundance of each ciliate species in the effluent
samples collected was calculated. The association ratings were
calculated according to Curds and Cockburn (1970) on the basis
of the frequency of occurrence of each ciliate in the four
BOD ranges of 0–10, 11–20, 21–30 and >30 mg/1. The frequency
of occurrence of each ciliate was transformed to a
number of points with a total of 10 points for each ciliate species.
The BOD range in which the highest totals occur was used
as a predicted effluent quality class in the form of very high
quality, moderate quality or low quality effluents (Curds and
Cockburn, 1970).