FINDINGS
Cell Numbers

The cell numbers were determined by photometric measurement of optical density. The means and standard deviations of the cell numbers of the control and the treatments are presented in the following table:

Nominal
Concentration in mg/L
Parameter Cell Number/mL
    0 h 24 h  48 h 72 h
0 Mean 2159 12759 58395 215783
0 SD 0 1265 10081 35092
1.0 Mean

2161

9348 60014 78699
1.0 SD 0 2715 35890 27528
10 Mean 2161 11144 65044 74387
10 SD 0 3297 6591 5394
100 Mean

*2159

*301484 *559844 *508460
100 SD 0 45755 10800 19947

SD = Standard Deviation

*At the test item concentration 100 mg/L the solution was clouded. Therefore photometric measurement was biased and the calculated cell numbers faulty and not usable for evaluation of the results.

Temperature, Light Intensity, pH

In the following table the pH values, the light intensity and the temperature during the test are stated:

  0 h 24 h 48 h 72 h 
Light intensity [lux]

5300

5300 5300 5300
pH Concentration in mg/L      
  0 8.7

8.0
  1.0 8.7 7.6
  10 8.7 7.6
  100 8.4 7.0

Microscopical Observations

In the following table, the appearance of the alga at the end of the test is state:

Nominal Concentration in mg/L Normal and Healthy Appearance of the Algae
0 Yes
1.0 Yes
10 Yes
100 No cells

Growth Rate and Yield

From the cell numbers, the Growth Rate μ and the Yield were calculated. The means and standard deviations at the end of the test are given in the following table:

Nominal concentration in mg/L   Growth rate [day -1]  Yield [Cell concentration/mL]
0 Mean 1.53 213622
SD 0.06 35085
1.0 Mean 1.19 76536
SD 0.11 27524
10 Mean 1.18 72224
SD 0.02 5388
100 Mean
SD

SD = Standard Deviation

*Because of clouded test solution not usable for evaluation of the results.

Inhibition

The following mean inhibition values were calculated for the Growth Rate μ and the Yield.

Nominal concentration in mg/L % Inhibition
Growth Rate μ Yield
0 0 0
1.0 22.54 66.14
10 22.94 66.16
100 *100 *100