معالجة الصرف الصناعى(العلاقة بين المجلطات وكفاءة الترسيب)2

Coagulation and Precipitation

Average raw samples transmittance was 48% with minimum value of 42%, and maximum value of 50%. different doses of coagulants verses the measured transmittance after precipitation for samples from the

the transmittance for the samples treated with alum, shows that the best transmittance’s 96%, took place at dose 250 ppm. The trend of the measurement shows more stable reading from dose of about 100 ppm than that of the low doses


the best transmittance, 80%, took place at dose of 200 ppm. The trend of the transmittance declines after the 200 ppm dose by about 3.6% at dose 250 ppm

.
the transmittance for the samples treated with ferrous sulfates, shows that the best transmittance, 94%, took place at dose 100 ppm. The trend of the transmittance declines after the 100 ppm dose by about 37% at dose 250 ppm may be due to the excess of the dose that makes the particles charge positive and form a repulsive force between the particles

the transmittance for the samples treated with ferric chloride, shows that the best transmittance, 97%, took place at dose250 ppm. The trend of the measurement shows increases of the transmittance as the dose increase.

The next two sets or results show the effect of using a mixture of two
coagulants of the same dose
.
the results of using a mixture of alum and ferric chloride with doses
from 50 ppm (25+25) to 250 ppm

. The peak transmittance reached 100% at doses 200 and 250. The trend is linear from dose 50 to 200 ppm, then it was stable at the 100%



transmittance. Finally, the use of two coagulants of alum and ferrus sulfates,
the highest transmittance (84%) took place at dose 150 ppm.

Nearly the transmittances were stable for all doses with average value of about 82%.

The best results were obtained using a combination of the alum and the ferric chloride that the transmittance reached 100% at dose 200 ppm (100 ppm of alum + 100 ppm of ferric chloride). However, the high dose of the chemical used may limit the application of the chemical precipitation for economical issues.