| As a matter of fact, with the fast industrialization tendency, water pollution and lake eutrophication in the world are still getting more and more exacerbated for a number of reasons, both human activities and natural factors. Luckily, attached algae are one of the important organisms in lake eco-system, whose growth is favorable for metabolizing and energy following on keeping aquatic ecosystem balance. Heretofore, algal biotechnology has been extensively studied and applied in improving water quality and removing nutrients and metals from eutrophic or contaminated waters. This paper is aimed to discuss the removal ability on nitrogen and phosphorus from synthetic wastewater and eutrophication lake water by attached algae. Four filamentous green algae (FGA), such as Hydrodictyon reticulatum ,Cladophora oligoclona,Pithophora oedogonia and Spirogyra sp. were studied in laboratory conditions. Results obtained from the study showed that the FGA could recover a large amount of nutrients from artificial wastewater during their growth. The highest removal ratio of TN and TP were 49.08% by Hydrodictyon reticulatum and 55.64% by Cladophora oligoclon, respectively. The average removal rates of TN, TP were 6.17mg·L-1·d-1 and 3.72mg·L-1·d-1 by Hydrodictyon reticulatum; 4.80mg·L-1·d-1 and 4.94mg·L-1·d-1 by Cladophora oligoclona ; 3.90mg·L-1·d-1 and 2.24mg·L-1·d-1 by Pithophora oedogonia; 5.64mg·L-1·d-1 and 3.07mg·L-1·d-1 by Spirogyra sp. respectively. Attached algal treatment system was setup two scales, one was operated in batch mode by recycling 140L synthetic wastewater. The algal community mainly composed of filamentous green algae with a most abundant species of Stigeoclonium sp. During the experiment, attached algae could grow very well in wastewater treatment system. After a 5-day culture, harvested algal biomass reached to 14.36 ±0.72g·m-2. Attached algae also showed a relatively high ability to removal nutrients. The removal rates of TP,TN,NH4-N and NO3-N were up to 96%,98%,98% and 97%, respectively. The contents of TN and TP in synthetic wastewater were changed from 36.97±0.26 mg·L-1 ,2.88±0.02 mg·L-1 to 1.44±0.09 mg·L-1,0.07±0.01 mg·L-1, respectively. The maximum average area removal rates of N and P were 1.84 and 0.15g·m-2·d-1. The other scale of attached algal treatment system was operated in batch mode by recycling 60L secondary effluent and eutrophic lake water, respectively. The test algae were mainly blue-green algae with the most abundant species of Oscillatoria princeps. Results obtained were as following: For secondary effluent, removal rates of TP and TN were up to 94.4%and 60.2%, average area removal rate of TP and TN were 1.142 and 0.008 g·m-2·d-1 average area algal production was 3.710 g·m-2·d-1,respectively. The contents of crude protein and TP of harvested algal biomass were 35.28±0.12% and 0.78±0.02%. For eutrophic lake water, removal rates of TP and TN were up to 93.8%and 79.6%, average area removal rate of TP and TN were 0.974 and 0.067 g·m-2·d-1, average area algal production was 4.729 g·m-2·d-1,respectively. The contents of crude protein and TP of harvested algal biomass were 45.26±0.265 and 1.38±0.02. Compared with the early algal nutrients treatment technique, Attached algae treatment systems were superior to micro-algae and suspended algae. It is concluded that attached filamentous algae have the potential for use in purification of wastewater and in control lake eutrophication. It could be served as a means to restore lake eco-system.
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