الفهرس 
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Abstract
Algae are simple microorganisms that are mainly aquatic and microscopic, living in saline, brackish or freshwater environments. Such organisms are able to convert sunlight, water and carbon dioxide into algal biomass. The green alga Chlorella vulgaris was used in this study.Different treatments were performed on the green alga Chlorella vulgaris to enhance biomass production as(1) Study the effect of different nitrogen sources on growth of Chlorella vulgaris by replacement sodium nitrate in BG-II medium by (0.53 g.l-1)urea. After cultivation period the results showed that the dry weight was(0.92 g.l-1) with growth rate (0.07 g.d-1), (0.59 g.l-1) in urea and sodium nitrate cultures respectively. Total chlorophyll showed an opposite manner, in sodium nitrate culture total chlorophyll was (37 mg.l-1) with growth rate (0.1 mg.d-1) but, urea was (18.2 mg.l-1) with growth rate(0.067 mg.d-1). Carotene was nearly equivalent in the two cultures (12.42 mg.l-1) and (12.69 mg.l-1) in sodium nitrate and urea cultures respectively. from the previous results urea is the preferred nitrogen source.(2) Study the effect of different carbon sources on the growth of Chlorella vulgaris. Different carbon sources were added to the BG-II medium to know the effect of each carbon source on the algal growth. The control was BG-II medium but sodium nitrate replaced by urea. Carbon sources were added in CO% basis present in urea (46.67%). A 0.5ml.l-1 of 96% analytical grade acetic acid, 0.39 g.l-1 oxalic acid, 0.56 g.l-1 citric acid and 0.72 g.l-1 sodium acetate were added. After the incubation period results show variations, acetic acid and sodium acetate were the best but oxalic and citric acid show less growth in dry weight, total chlorophyll and carotenes.