الفهرس 
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Abstract
Lake Mariut is one ot the main northern lakes in Egypt. The Lake extends along the Mediterranean coast and represents the southern borders of Alexandria City. It lies between latitude 30°:07” to north and longitude 29°:57 “to the east along the Mediterranean covering an area of 65 km2 (almost 15.500 feddans). It is divided into five basins, which are somewhat interconnected to each other by several breaches in the dykes of El-ummum drain and canal. The Lake depth ranges between 1 -3 meters.
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Until the eighties, most of Alexandria’s domestic sewage and much of the industrial wastewater were discharged directly into the Mediterranean Sea through a number of outfalls along the coast of Alexandria. Pollution of beaches and the inshore waters caused severe impact on Alexandria as a summer resort which forced the local authorities to divert these discharges into Lake Mariut‘s Main Basin. At that time, the discharge consisted of raw sewage without any treatment what so ever mixed with industrial effluents. The lake’s main basin became highly eutrophic and polluted with various chemicals. In addition to the problem of organic inputs, there were many hazardous discharges. Latter, two primary treatment plants were built and started operation in the nineties. The sewage water passes through screens and then sedimentation tanks and a dewatering facility to remove the sludge. Furthermore, some untreated wastewater is discharged directly into the Lake. Excessive eutrophication of lakes is a serious international problem. There has been a great need for a comprehensive information source usable in developing future rehabilitation/protection programs. This state-of-the art review represents an attempt to delineate the accomplishments of lake restoration-related activities worldwide Lake water eutrophication has become one of the most important factors impeding sustainable economic development in China
Restoration means a return to pre-disturbance conditions and relies on historic landscapes or ecosystems as models. It is the most demanding of management paradigms and implies complete re-creation of a system equivalent to the model. Restoration represents the extreme on a continuum of management protocols and is valuable as an ideal. In most cases, it is impractical, uncalled for, or even impossible. Rehabilitation is the repair and replacement
of essential ecosystem structures and functions in the context of Eco regional attainability in
(3)
order to achieve specified objectives .
To succeed in combating Lake Eutrophication, cooperation of local inhabitants, small factories, and farmers in reducing phosphorus discharge is very important. But the willingness of each player to cooperate would depend on the cooperation of other players and on the level of environmental concern of the society in general (4), Schallenberg et al stated that Lakes provide a wide range of ecosystem services and substantial economic benefits to various regions of New Zealand (5) .However, the financial cost of Lake Restoration or rehabilitation.