New Bugesera International Airport - Conceptual Design of Infrastructure (Wastewater Treatment, Water Supply, Waste Management)

Detailed project description:

Background:

The existing capital airport of Rwanda in Kigali will be replaced by the "New Bugesera International Airport - NBIA". As the new site is a greenfield, all required infrastructure for the new airport has to be developed according to ICAO standards. For the conceptual and preliminary design phases, HYDROPHIL was asked for support services for infrastructure planning in the fields of sewerage, wastewater treatment, water supply and waste management.

Objective:

The purpose of the project is the safe supply of the entire airport with drinking water as well as the safe disposal of waste and wastewater. The specific objective of the project is to provide conceptual and preliminary designs (the latter only for the WWTP) together with cost estimates as the basis for the further detailed design.

Services:

- Conceptual design of sewer system resulting in the following key system characteristics:

The conceptual design of the wastewater conveyance system has taken full advantage of the permitting topography to have gravity sewer (I = 0.0025 – 0.037) as opposed to pumping mains which have high operating costs. The total length of network is ca. L=3.85 km with diameter varying from DN200 to DN500. Aircraft wastewater is collected by a vacuum truck and delivered to a tank from which it is discharged to the aircraft wastewater tank located directly at the WWTP (“black wastewater buffer tank”). Surface water from Aircraft Rescue and Fire Fighting (ARFF) training place and washing place for aircrafts is discharged via drainage system as long as neither ARFF training nor aircraft washing are carried out. In the case of ARFF trainings or aircraft washing, floor drainages leading to surface water drainage system will be closed and floor drainage to sewer system opened to enable discharge of contaminated water to the WWTP. From the WWTP, effluents are to be discharged to the next recipient with sufficient capacity for expected immissions from WWTP.

- Conceptual and preliminary design of WWTP resulting in the following key system characteristics:

Expected total daily average wastewater flow Qd,ave generated to the WWTP is approximately 695 m3/d. A conventional biological WWTP (mechanical treatment, biological treatment, final clarifiers) with nutrients removal and subsequent disinfection (recommended for wastewater discharge in tropical areas; dosing of NaOCl or alternatively UV disinfection; disinfection would also allow use of treated wastewater e.g. for irrigation purposes, if desired) is proposed. Effluents from the WWTP in its final expansion will meet all requirements according to Directive 91/271/EEC for “sensitive recipients”. Excess sludge will be treated in such a way that it may be incinerated or transported offsite for disposal in a landfill or used as an agricultural soil amendment.

- Conceptual design of water supply system resulting in the following key system characteristics:

Maximum hourly demand of 200 m3/h (56 l/s) with a pressure of 6.5 bars is guaranteed from the connection point with the water supply source (DN250 pipeline from Gahembe reservoir located on the west of the airport area)

Total length of network is ca. L=8.3 km with diameter varying from DN50 to DN250.

As backup in case of a breakdown in the transmission system, storage pumping will be provided to deliver the water from ground tanks to the various airport facilities at the required pressures. The volume of the pumping storage is 1,000 m3 which covers the maximum day water demand for 1 day. A pumping station equipped with variable speed pump batteries is switched after the reservoir to deliver water with adequate pressure in the network. The pumps are sized according the largest head of 55 m with a maximum capacity of 200 m3/h. Since firefighting will be guaranteed from a separate water retention pool, no hydrants are connected to this water supply network. An emergency connection for filling the water retention pool which serves the firefighting network can be operated manually.

- Conceptual design of waste management system

- Cost estimates