Rehabilitation and water quality monitoring in the Golden Horn.

In this work, the oceanographic aspects of the Golden Horn and some results of the Golden Horn Rehabilitation Project are presented. The hydrographic structure of the Golden Horn responds rapidly to the conditions in the southern Bosphorus, which is especially true for the outer parts of the estuary up to the Valide Sultan Bridge (VS). West of this bridge which was blocked by the pontoons of the bridge, carries the major pollution load and is dependent on the underlying water and surface mixing, for its renewal. The dissolved oxygen concentrations were measured below the detection limit in the region between the VS and Eyüp-Sütlüce (ES) section during the majority of the measurement periods where H2S has been determined simultaneously until February 2000. Although the microbial contamination of the estuary stations is very high, decreases in the contamination at stations are observed. The highest concentrations are recorded at the ES-VS section and supported by Fecal Coliform data during the rainy months in general despite the operational collector system surrounding the estuary. An obvious decrease of pollution in comparison with the data of the previous years is clearly observed as an encouraging result of the rehabilitation efforts achieved so far.

Centralised versus decentralised treatment and disposal options for Küçükçekmece Basin of Istanbul city.

Küçükçekmece Lake is a sea lagoon located on the European side of Istanbul city with a drainage area of 4 million inhabitants (year 2040). The original plan to treat all of the wastewater collected from the drainage basin in a single plant located at the Northern end of the lake is compared with the decentralised option involving 4 treatment plants. The initial investment cost of the decentralised option is estimated to be higher than the original plan by an amount of 43 million US $. However, the decentralised option has been chosen finally, considering the low cost and risk of wastewater collection, the possibility of the staging of the services, and the reduced environmental impacts.

Detachment mechanisms of deposited material in a backwashed filter.

Theoretical and experimental studies were performed to evaluate the detachment mechanisms of deposited material by fluidizing the filter media. The hydrodynamic characteristics of a backwashed filter and the energy dissipation during backwashing processes were investigated. The existence of a viscous sublayer around each fluidized particle and laminar sublayer thickness at the wall were neglected. Direct measurements of the effluent turbidity Te and the total backwash water volume Vbt were made during backwashing in the laboratory experiments. Some relationships applicable to backwashing processes were developed with good accuracy. The turbulence parameter C0.5(a)/Re which characterizes the effect of turbulence fluctuations in a backwashed filter increased with increasing fraction solids (1-epsilon) and decreased with increasing the Reynolds number of the flow Re. The detachment rate of deposited material rd, was found to vary with hydrodynamic shear (taua), turbulence fluctuations (C0.5(a)/Re) and backwash water volume (Vb). Maximum shear stress caused a maximum detachment of the deposited material from the filter media. The detachment rate of deposited material rd had a minimum value at the turbulent parameter of 0.9 and fraction solids of 0.3. Also the detachment rate of the deposited material rd decreased with increasing the unit backwash water volume Vb which is the ratio of the total backwash water volume Vbt to the expanded bed volume Ve.

Planning of wastewater treatment and disposal systems of Istanbul metropolitan area.

Current and future wastewater treatment and disposal strategies of Istanbul city are presented. Istanbul is the largest city of Turkey and has a population of 10 million that may reach about 20 million in 2032. The city is divided into Asian and European sides by the Bosphorus Strait. The Sea of Marmara is an enclosed sea, connected to the Black Sea and Aegean Sea by the straits of Bosphorus and Dardanelles. Therefore, there is very strong and permanent stratification in the Sea of Marmara throughout the year, lower layers carrying Mediterranean and the upper layers carrying Black Sea water. This unique coastal structure of Istanbul necessitated a detailed study to determine the level of wastewater treatment and the location and depth of marine outfalls. A comprehensive three-dimensional water quality modelling study concluded that tertiary treatment including nitrogen and phosphorus removal is required for the effluent discharges into the Marmara Sea. However, enhanced primary or even primary treatment has been found satisfactory for discharges into the lower layers of the Bosphorus and into the Black Sea. Provisions for upgrading to secondary treatment were recommended. The status of existing and planned wastewater treatment plants and sea outfalls of Istanbul city are also presented. Although the amount of treated wastewater was only 63 percent in 1998, a target of 95 percent treatment level by the end of 2000 has been adopted in implementation plans. All treatment plants are located at or close to the coast except Pasakoy WWTP which is in the catchment area of Omerli Reservoir, the major source of drinking water for Istanbul city. The Pasakoy WWTP has been designed to treat wastewaters collected from the catchment area of Omerli Reservoir to tertiary level before ultimate disposal. The implementation programme together with the cost estimates are given. Total investment on water, wastewater and stormwater projects up to year 2032 is estimated at about 10 billion US Dollars. The share of the wastewater projects in this total is increasing with time. The financial analysis concluded that investments for a Higher Demand Scenario can be realised by raising the water tariffs to 1.0 $/m3 for Phase 1 and 0.9 $/m3 for Phase 2.