Retrofitting and Extension of a WWTP in Saudi Arabia with UASB and MBR technology

In order to treat the increased volume of wastewater and to achieve stricter effluent values, the existing wastewater plant was completely upgraded and an anaerobic stage (UASB) was added.

CONCEPTUAL FORMULATION

The wastewater treatment plant for a soft drink manufacturer in Saudi Arabia was designed in a way to reliably stay well below threshold values which are stated by the authorities of the city of Dammam. Part of the wastewater stream is even further treated and recycled in the production processes as e.g. cooling water in the cooling towers.

The confined space conditions and the highly polluted wastewater with biodegradable organic substances led to a process design combination of an anaerobic UASB (Upflow Anaerobic Sludge Blanket) reactor and an aerobic MBR (Membrane Bioreactor) system.

The combination of mechanical preatreatment and the UASB reactor fulfilled the effluent threshold values of the city. One third of the anaerobically treated wastewater is further treated in the MBR step.

The UASB reactor is a biological and anaerobically working high-load reactor which is filled with particular granular biomass which is kept via continuous recirculation in a suspended state. Die organic load is decreased by 80% within the reactor. Low operational expenditures can be achieved as no aeration and low maintenance work is required. Furthermore, biogas is produced which can be used in a CHP or can be simply flared off.

The membrane bioreactor system has an ultrafiltration membrane, and hence, achieves a solid free, pristine water quality that can be unhesitatingly directed to a reverse osmosis plant for further treatment.

Aerobic surplus sludge resulting from biomass growth in the aerobic biological system is dewatered by a continuous working sludge press and the stabilized, dewatered solids are eventually getting disposed.