Environmental Engineering Reference
In-Depth Information
determined by the Vanadomolybdophosphoric acid colorimetric method and represent the
total reactive phosphorous. Ammonia was determined by a direct Nesslerization method,
followed by a spectrophotometric measurement at 425 nm wavelength. Nitrates were
determined by the Cadmium reduction method, followed by spectrophotometric
measurement at 540 nm wavelength.
Statistical calculations (descriptive statistics and one-tiled Student's t-test - unequal
variance, at 90% of confidence) were performed using the Microsoft EXCEL statistical
package. Throughout the text of section 5, significant difference means that p< 0.1 for
mean's comparison.
5.2
Results and discussion
Results for DR1 and DR2, as the annual mean and median values, are shown in Fig. 3.5
and Fig.3.6 respectively. Additional statistical data is presented in Table 3.5. Results are
discussed and compared to the blue classification of effluents discharged to surface water
(WWEDR 2000), which could be regarded as the safe natural water quality limit and is
referred in the text as the “prescribed” limit. The
Figure 3.4. Schematic representation of
the drainage areas and discharge points
of DR1 and DR2, DRA-drainage areas;
DP - discharge points.
