الفهرس 
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Abstract
Nowadays, sewage effluents are used on a wide scale to overcome the lack of the fresh water required to irrigate arable lands and the newly reclaimed ones as well.
These effluents contain heavy metals harmful to plants and microbial pollutants harmful to human.
This investigation aimed at evaluating qualitatively and quantitatively the sewage effluents of El-Berka and Helwan wastewater treatment plants used for irrigating El-Gabal El-Asfar farm and EI-Saff region, respectively. To fulfill these purposes, sewage effluents were monthly sampled from El-Berka wastewater treatment plant at three sites namely the inlet, the outlet and at 2 km away from the emergency canal to which the treated effluents are deposits. Also, effluents were sampled from Helwan wastewater treatment plant at three sites namely the outlet of the plant, the beginning of El-Saff El-Gadida canal to which the treated effluents are disposed and at 3 km apart from the beginning of the aforementioned canal.
The sewage effluents sampling of the above mentioned sites was run over a period extended from September 1999 to August 2000. The soil as a final sink of the above mentioned pollutants was also undertaken into consideration.
The obtained results could be summarized in the following:
♦pH values of the studied sewage effluents were generally natural to slightly alkaline and fluctuated within a very narrow range due to site and time of sampling.
♦EC values of the effluents at the inlet those at the outletaveraged 1.07 dSm-1
♦The EC values of the sewage water discharge from Helwan wastewater treatment plant ranged from 1.71 to 2.34 dSin-1 at the outlet, 2.01 to 2.87 dSm-1 at the beginning of El-Saff El- Gadida canal and 1.99 to 2.30 dSm-1 at 3 km apart
from the beginning of this canal.
♦The chemical composition of the sewage effluents and waters revealed that Na+ dominated the cationic composition whereas Cl- dominated the anionic one.
♦Regarding the sewage effluents content of the trace elements, it could be observed that Co2+ was not found in detectable concentration in all sites El-Berka and Helwitn plants, Pb ranged from 0.01 to 0.05 mgL-1 in the effluents of LI-Berka anf from 0.0I to 0.02 in the effluents of I lel wan Cd ranged from not dectable concentration to 0.04 mgL-1 in the sewage effluents El-Berka whereas it did not exceed 0.02
mgL-1 in the effluents of Helwan.
♦Thus, the studied sewage effluents are safe from the stand points of both Co and Pb on the other had concentration of sometimes exceeded the maximum permissible level whereas Ni in all the studied effluents exceeded the
permissible level. (0.2 ingL-1)
♦According to USS lab. Richards, 1954] the sewage effluents of El-Berka plant belong to C3 category which means that these effluents can not be used on soils with restricted drainage while those of Helwan fluctuate between C3 and C4 whose water may be used occasionally under very
special circumstances.
♦The SAR values of all the studied sewage effluents wereless than 10 i.e these effluents can be used for irrigation with some danger of the development of harmful level of exchangeable sodium.
♦Boron concentration was less than 0.33 mgL-1 which means that the studied effluents are safe from this stand point of view.
♦Also, RSC values were all negative, thus the investigation sewage effluents are suitable for irrigation
♦According to classification of Gupta (1979) for irrigation water and values of Adj SAR which were lower than 10 and Boron concentrations which were less than 1 mgL-1 the sewage effluents under study could be considered normal water. Also, values of EC of the sewage effluents of El-Berka put these effluents in the first grade i.e normal water, however the corresponding values of Helwan sewage effluents revel that these effluents belong to the second grade C2.
♦PH values of El —Saff soil which was irrigated with the sewage effluents decreased slightly be increasing period of irrigation with these effluents up to 7 years.
♦Also, soil salinity and content of CaCo3 decreased whereas organic matter content increased by prolonging period of irrigation.
♦Soil contents of DTPA- extractable Co, Pb, Cd and Ni increased obviously due to irrigation with the sewage water. The increase became more pronounced by increasing period of irrigation with this sewage water.
♦In spite of the mechanical, chemical and biological treatments of sewage effluents, under study, the final effluents remained containing a lot of bacteria whose ,counts, wereenormoused once again in some sites due to the human activity.
♦ A though chlorination process could succeed reducing densities foeacol conforms at sites 2 and 3 of El-Berka, the residual counts were still high and did not fit with the WHO (1989) guidelines for unrestricted irrigation or with the Egyptian law 48/1982 regulating canals or drains which recommended counts of less than 1000 cell of conforms per 100 ml.
On the other hand, chlorination could reduce faecol colifoims at all effluents of Helwan to counts in a good agreement with the WHO (1989) guidelines and the Egyptian law.