Decentralized Sewage Utilisation
for Irrigation of Green Areas in Arid Cities


BMBF sponsored joint research project


Project title: Decentralised raw wastewater utilisation for irrigation of green areas in arid cities (case study in the UAE)
Project leader: Prof. Dr. Dr. Karl-Ulrich Rudolph
Co-operation partner: HUBER SE; American University of Sharjah
Sponsor: BMBF (Federal Ministry of Education and Research) - PTKA-WTE
Reference number: 02WD0757
Project term: June 2006 - December 2011


Background

Green spaces are essential for life in arid urban areas as they positively influence the local climate and reduce the appearance of dust. To keep these spaces in a proper condition despite arid climate they have to be intensively irrigated. Even in regions with scarce water resources, mostly potable water from public water supply systems is used for this purpose, resulting in an increasing lack of water for higher-valuable uses. On the other hand, particularly in arid developing countries, completely uncontrolled use of raw wastewater for irrigation purposes is widely spread, with all the hygienic problems linked to this.

To address these issues, aim of the research project is the development of a decentralized tretment concept for controlled utilisation of sewage as irrigation water in public green spaces. The concept shell be demonstrated by a pilot system using wastewater diretly from the existing sewage system.

Aim of the project is not to offer a costly full purification facility for sewage but a comparatively efficient system with partial treatment and disinfection of raw wastewater, only as far as it is necessary for the specific use in urban green spaces.

Development of a pilot system

Wastewater reuse for public green spaces requires appropriate wastewater disinfection as the main objective. Reduction of organics, nutrients etc is usually of minor relevance, as nutrients are often needed as fertiliser. Therefore, the technical treatment concept has to be focused on the mechanical purification and disinfection of wastewater. To make it reliable especially for decentralised applications, the complete treatment unit should be as compact as possible and flexible regarding the conditions of the application locality.

Schematic scheme of pilot system

Funded by the German Federal Ministry of Research (BMBF), a specific pilot system has been developed, fulfilling these demands. As schematically displayed in figure 1, the system consists of four main components:
  • a pump to feed the system with raw sewage from existing sewage systems,
  • a mechanical separation of solid wastes by a pipe strainer,
  • a sedimentation tank with lamellas to reduce the suspended solids,
  • a following disinfection unit with UV-radiation.
    •

    The compact system can be located next to a manhole of the sewage system.

    Practical application

    The trial operation of the pilot system is conducted in United Arab Emirates (UAE). There the project is supported by the local branch of HUBER SE and the American University of Sharjah.

    Multi-barrier strategy

    In addition to the technical concept, a multi-barrier strategy for hygienic risk management regarding irrigation of public areas with wastewater has been outlined, as there are:
      1.) Water reutilization suitable for the site conditions
           (like geological situation, kind of plantings, etc.),
      2.) Way of handling suitable for the water reutilization
           (e.g. regarding transport and distribution of the irrigation water),
      3.) Treatment suitable to the way of handling of raw sewage
           (especially regarding pathogen reduction).

    Experimental verification of the treatment process

    Literature review has shown that there is little knowledge about disinfection of only partially clarified wastewater. At previous projects different disinfection technologies have been researched. UV disinfection was identified as the most appropriate disinfection technology in this context.

    Within the project experiments with filtration, sedimentation and UV disinfection on laboratory scale are carried out, technically supported by WEDECO, ITT Water & Wastewater. One research focus deals with the efficiency of UV disinfection at only partially pre-treated wastewater.

    Accompanying socio-economic study

    To verify the feasibility of the concept, an accompanying socio-economic study will be drawn up, taking into consideration the specific local and regional conditions.


    Downloads

    Project abstract
    Paper of Rudolph, Fuhrmann, Soud - Decentralized sewage utilization - WRRS 2007
       (125 KB)
    Poster - Decentralized Reuse of Wastewater - HUBER-Symposium 2007 (42 KB)
    Poster - LET 2009, Singapore (5.5 MB)