Algal production 241Oron and Shelef formula
To account for the effects of environmental and operational conditions on algal
growth in HRAP, Oron and Shelef (1982) proposed the following empirical
formula.
Ca = a. (HRT/z)b .Ioȕ .Tr (5.6)Where,
Ca = algal concentration, mg/L
T = ambient temperature, °C
a,b,ß,r = constants, dimensionlessUnits of HRT, z and Io are days, m and gcal/(cm^2 -day), respectively.
The numerical values of these constants were determined from the data
collected from pilot- and field-scale HRAP operating in Israel. By applying the
nonlinear least-square method, the following equation was derived:
Ca = 0.001475(HRT/z) 1.71 Io0.70T1.30 (5.7)The related algal productivity, Pa in g/(m^2 -day) may be given by:Pa = Ca(z/HRT) = 0.001475(HRT/z) 0.71 Io0.70 T1.30^ (5.8)An experiment was carried out in Israel with domestic wastewater (average
BOD 5 of 400 mg/L) and algae such as Micractiniumpusillum, M.quadriesetum
andScenedesmus dimorphus in HRAP. Table 5.9 shows the predicted algal
concentrations using Equation 5.7 and measured algal concentrations during 6
seasons. The results of this experiment show the applicability of Equation 5.7
for the assessment of algal concentration in HRAP.
Some drawbacks of Equation 5.7 are that it is applicable to influent BOD 5
ranging from 200 to 400 mg/L and to Israel conditions where these experiments
were carried out. However, the same approach can be applied to suit other local
conditions, but with different values of a, b, ß, r.
Theoretical estimation
Equation 2.6 implies that one mole of algal cell (molecular weight 154 g) is
synthesized with production of 7.62 mole O 2. Therefore, as previously state in
Equation 5.4, 1 g of algal cell is equivalent to: