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Purification of wastewaters from the region of Niš is discussed in the General Design of a Purification Facility for Urban and Industrial Wastewaters of the City of Niš (Institute for the development of water resources "Jaroslav Černi", 1998.-2000.)

Field investigations included discharge measurements at existing sewage outlets, quality tests of urban and industrial wastewaters, and surveys of industrial pollutants in Niš (Institute performed in 1998. two cycles of discharge measurements at three main sewage outlets over a period of 7 days; wastewater quality was testing by collecting composite bi-hourly samples).

All wastewaters of Niš are currently evacuated to River Nišava by means of several independent outlets. The main guidelines of future sewage system development are discussed in the Urban Plan. Separation systems are envisaged for the new suburbs. Wastewater sewage would be linked with the existing system in order to evacuate all wastewaters to the purification facility.

The most significant works related to the inter-connection of the sewage system to form a single functional entity should be implemented by constructing a main collector between the 12 February Boulevard, the Beogradmala collector, the passage beneath River Nišava and the Nišava collector, with an overall distance of 10 km.

(*) Niš city sewage system - future state
(2010. god.)

The following values are selected for sizing the purification facility:

PRESENT STATUS (PHASE I)

	Maximum daily discharge = 120 000 m3dan-1
	Maximum hourly discharge = 2.0 m3s-1
	Mean organic load (BPK5) = 20 000 kg dan-1
	Mean BPK5 concentration - dry period = 160 gm-3
	Mean SM concentration - dry period = 200 gm-3

During precipitation, a maximum of 4.0 m³s^-1 would be delivered to the facility, including dilution at the weir (1+1). The contribution of organic pollutants amounts to 30% BPK₅.

	Mean concentration during wet period (BPK5) = 100 gm-3
	Mean value of precipitation load = 40 gm-3

FUTURE STATUS - PHASE II - 2010.

	Maximum daily discharge = 250 000 m3dan-1
	Maximum hourly discharge = 4.0 m3s-1
	Mean organic load (BPK5) = 30 000 kgdan-1
	Mean BPK5 concentration - dry period = 150 gm-3
	Mean SM concentration - dry period = 200 gm-3

The following criteria were used in the preparation of design documentation:

	The purification process shall be proven in contemporary practice;
	High degree of purification, over 90%;
	To the greatest extent possible, select procedures for which equipment can be maintained and serviced locally;
	Provide output concentrations after purification of BPK5 = 20 mg/l and SM = 30 mg/l.

Following assessment, single-stage biological purification with bioaeration by means of compressed air was selected as the water purification process. Mud would be treated by anaerobic digestion, most common in facilities of this size. The procedure allows the use of biogas to drive the facility. Based on an assessment of the energy balance, most of the energy requirements of the facility can be met by its own production.

Institute for the development of water resources "Jaroslav Černi", 2001.