الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
In the present investigation the design performance of an algal aquaculture wastewater treatment system is developed. The performance of the mass culture predominated mainly by the green algae Scenedesmus spp. and Chlorella vulgaris was assessed in a pilot scale level in the batch and continuous cultures.
1- A survey of the algal community of the wastewater under treatment at the Beni-Suef wastewater treatment station revealed the following:
• The existence of algal species belonging to each of the four main algal groups; Cyanophyta, Chlorophyta, Bacillariophyta and Euglenophyta. Euglenophyta and Chlorophyta contributed the major bulk of the algal population and reached approximately 34.2 and 33.6%, respectively. Meanwhile, The population of Bacillariophyta and Cyanophyta accounted for 21.3 and 10.97%, respectively.
• Wastewater harboured high densities of hlitzschia acicularis, Phacus nordstedtii and Scenedesmus dimorphus.
• Aquatic algal treatment induced a reduction in the total number of all the identified species to only 15 species upon applying the batch system, belonging to Cyanophyta, Chlorophyta and Bacillariophyta with the disappearance of all members of Euglenophyta.
• A total of 17 species representing the 4 main algal groups were detected in the continuous system by the end of the treatment period with the predominance of Chlorophyta (8), Bacillariophyta (4), Cyanophyta (3) and Euglenophyta (2). The latter group contributed only very small percentage.
• Treatment resulted into a high density algal population with total count reaching 7.2 to 7.6 x 103 units T1 which accounted for approximately 47-49
times increase by the end of the treatment period.
• Chlorophyta offered a high density culture environment throughout the aquatic treatment period. The total chlorophycean count constituted a percentage of about 99.4 to 99.5%.
• The genus Scenedesmus dominated the Chlorophyta group and provided five species which constituted approximately 64.96% with the predominance of Scenedesmus obliqus 19.35% in the continuous culture. The Scenedesmus spp. in the batch culture were identified as S. bijuga (19.35%), S. opoliensis (13.8%), S.dimorphus (13.8%), S.obliqus (13.55%) and S. longus (11.6%).
• Chlorella vulgaris constituted 27.65 and 34.34% of the total algal count in the batch and continuous systems, respectively, by the end of the treatment period. Chlorella together with Scenedesmus species provided the mass culture and played an important role in wastewater purification.
Estimation of the algal growth parameters by measuring optical density at 800 nm and determination of the chlorophylls contents indicated an increase in algal growth by increasing treatment time.
• Application of the batch system induced a much higher growth rate during the early treatment period. Generally, higher levels of chlorophylls a , b and c were measured in samples removed from the batch system and the level of Chi a reached its maximum after 28 days.
• Among the Cyanophyta, the total population reached its maximum level after 12 days (7.2 times increase) whereas longer treatment time induced marked reduction (88.2%) in the total Cyanophycean population.
• The ratio of Chi alb as well as Chi c level were relatively higher during the early periods of treatment.
• Separation of the algal biomass indicated a progressive gain in fresh and dry weights by longer treatment periods.
3- Monitoring the efficiency of the algal culture in removal of phosphorus, nitrogen and ammonia indicated the following:
• The continuous system displayed a gradual elimination of phosphorus, however, the batch system exhibited a different pattern where it induced P accumulation during the treatment for 42 days. Both systems efficiently depleted the water body of any detectable P by the end of the treatment period.
• The data revealed an initial increase in nitrate - nitrogen, however, longer treatment time induced a drastic reduction. The efficiencies of the system in nitrate removal reached 100% after 36 and 48 days in the batch and continuous systems, respectively.
• A significantly different removal pattern was demonstrated for ammonia with a gradual reduction in its level by increasing treatment time. However, the efficiency of the continuous system was relatively higher. The maximum efficiency was detected after 42 days (100%).
4- Treatment induced a progressive reduction in both COD and BOD to values below the discharge limits. The average total percentage reduction reached 89 and 91.7% in the batch and continuous systems, respectively. The system efficiently achieved a total of 84% in BOD reduction.
5- Assessment of the efficiency of the algal culture in wastewater and nutrient synthetic media showed the following:
• The applied aquatic systems demonstrated percentage reduction in the wastewater content of the heavy metals Fe, Zn, Mn, Ni, Cr,Cd and Co in the range between 52.3 and 100% in the batch system and 64.2 and 100% in the continuous system.
• Elevated levels of Fe were detected in wastewater samples and reflected by a relatively high bioaccumulation percentage of Fe in the algal tissue. The efficiencies of the systems in Fe removal reached 98 and 96.5% for batch and
continuous systems, respectively.
• A relatively lower reduction levels were obtained for Zn in the batch (85%) and the continuous (77.4%) systems, whereas the algae tissue accumulated low levels of Zn.
• Fe and Zn content of algae tissue grown on synthetic nutrient medium exhibited much lower levels as compared to wastewater grown algae.
• The system performed 100% removal efficiency in Mn removal, however, the algal tissue accumulated only minute amounts of Mn. Nutrient meduim supported a relatively lower Mn level in algal tissue.
• Algae accumulated only minute amounts of Cr although the removal percentage from the water body accounted for 77.5 and 95% in the batch and continuous systems, respectively.
• The system exhibited only moderate levels in Cd removal and reached 52.3 and 64.2%, however, it did not correlate with its level in the algae tissue. The estimated levels of Cr and Cd in the medium grown algae were higher (approximately 2 times) than wastewater grown algae.
• Ni removal accounted for 81 and 77.3% in continuous and batch system, respectively. Algal tissue accumulated minute amounts of Ni in both nutrient medium and wastewater.
6- Slightly high protein levels reaching 44.8% and 42.1% were estimated in algal tissue grown on nutrient medium and wastewater, respectively.
• Wastewater supported algal growth with the incorporation of a significantly higher content of individual amino acids Asp, Thr, Ser, Glu, Gly and Tyr and a markedly higher level of Pro. Meanwhile, His, Lys and Arg were markedly reduced, as compared to synthetic-medium grown algae.
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7- The fatty acids composition of the harvested algal tissue indicated variation in total lipids depending on the growth media. The level of saturated fatty acids were lower in wastewater grown algal tissue/ whereas the biosynthesis of all the identified unsaturated fatty acids showed an increase ranging from 30 to 69%, except oleic acid.
• Generally, wastewater induced an increase in all the detected fatty acids of the polar lipids, except oleic acid biosynthesis which was drasticaly reduced by 96.5%. Major contribution was demonstrated by the unsaturated Clg fatty acids, especially the di-and polyunsaturated acids. The C14 contributed minimum level.
• Wastewater grown algae content of phospholipids reached 3.5 times higher than its level in nutrient- grown algae.
• A coloured atlas is provided with 3 plates with the main algal taxa inhabiting the wastewater under investigation.