Organic Waste Recycling

242 Organic waste recycling: technology and management

Table 5.9 Environmental and operational conditions and predicted algal concentration
(dry weight) of the HRAP in Israel (Oron and Shelef 1982)

Solar radiation,
Io (gcal/(cm^2 -
day))

Ambient

temperature

(oC)

Effluent

depth

z, (m)

Retention

time,

HRT

(days)

Measured algal

concentration,

Ca (mg/L)

Predicted algal

concentration,

Caa(mg/L)

Spring 1977 576 14.6 0.45 4 176 173
Summer
1977

679 24.2 0.45 2.9 229 215

Fall 1977 393 21.4 0.4 3.4 210 201
Winter
1977/8

318 13.8 0.45 3.9 95 101

Spring 1978 538 18.9 0.35 2.9 240 204
Summer
1979

649 25.4 0.25 2 285 321

aAlgal concentration was predicted from Equation 5.7

7.62 x 32

= 1.58g O 2

154

or the factor

Weight of O 2 produced

p = = 1.58

Weight of algal cell synthesized

The oxygen demand of a waste is met through photosynthetic oxygen
production; the ultimate biochemical oxygen demand, Lt in any time t, may be
substituted for oxygen produced, and algal concentration Ca may be substituted
for weight of algal cell synthesized. Therefore:

Lt

p = (5.9)

Ca

Lt z

and algal productivity Pa, in g/(m^2 -day) =. (5.10)

p HRT

Where the units of z, HRT and Lt are m, days and mg/L, respectively.

Oswald and Gotaas (1955) reported that under environmental conditions
suitable for photosynthetic oxygen production, the value of p is normally