2.4.03 Export-oriented research & development – transfer to other countries

A joint research project funded by the Federal Ministry of Education and Research (BMBF) has documented results of German water research and developed them to suit other conditions. For this purpose, reference values were determined for the size and operation of water treatment and distribution plants while taking extreme untreated water properties as well as other climatic and social conditions into account. Ten institutes and universities participated in the project.

In the following, treatment methods tried and tested in Germany are assessed as to their applicability under special boundary conditions or when improved performance is to be expected.

Slow filters with closed bottoms and infiltration ponds with subsequent groundwater recharge represent possible alternatives for small systems in rural areas and cities of developing and emerging countries. It should be noted that slow filtration without pre-treatment should only be used to process low-turbidity water with minimal microbiological contamination.

Wealth of experience in bank filtration

Since bank filtration has been used in Germany for over 100 years, the country has a wealth of experience in this area. This knowledge can be employed for targeted application in other nations – despite the existence of different climatic and hydrogeological conditions. To support this transfer of knowledge, the project participants developed a range of engineering aids and provided detailed descriptions in the form of user guidelines (see references at end of article).

A combination of flocculation, sedimentation and filtration is the standard procedure employed by many countries for the treatment of surface water. Important considerations during project planning are optimum hydraulic and technical conception with regard to the addition of processing agents for flocculation, the minimisation of flushing water requirements, optimised sludge water discharge as well as the use of measurement and control technology adapted to local standards.

Micro- and ultra-filtration – an alternative to conventional water treatment

In addition to conventional water treatment by means of flocculation and filtration, micro- or ultra-filtration represents a possible alternative for turbidity removal purposes. These processes can be used to purify either lowturbidity untreated water without pre-processing or highturbidity untreated water following conventional pre-processing. Micro- and ultra-filtration is also a suitable means of processing eutrophic water. Sustainable use of these techniques requires an appropriate infrastructure for maintenance and operation.

The removal of heavy metals using ion exchangers is particularly suitable for low-turbidity water; the capacity of the ion exchangers is barely reduced. In the case of water containing heavy metals, ion exchange can be an alternative to treatment via flocculation, for example.

Particularly when used with waters containing unknown compositions of water-based substances, the by-product generation connected with oxidation processes and removal of residual content must be taken into account. The combination of hydrogen peroxide and UV radiation has proven to be a very energy-intensive process; pre-oxidation with potassium permanganate is not an effective means of enhancing the turbidity removal capacity of flocculation. Important planning criteria are the operational reliability of the process and the necessary qualification of the relevant personnel. The deficiencies of biological ammonium oxidation in cold water can be countered by a number of means. However, at water temperatures under 5°C, extremely long treatment periods (weeks to months) are required to eliminate high ammonium loads, which could effectively outweigh the benefits offered by the procedure.

Suitability of treatment processes in industrialised (IC), emerging (EC) and developing countries (DC)
+++ Minimal expenditure or state of the art
++ Moderate expenditure or not yet widely used
+ Higher expenditure or availability only in specific cases

Activated carbonCollective name for a group of artificially produced, highly porous carbons with a sponge-like structure. This pure material is characterised by its large specific surface area (up to 300 m2/g). Activated carbon is manufactured from peat, wood, lignite, black coal or nutshells. The materials are first carbonised, during which tiny pores are created. Activated carbon adsorbs organic substances from water and the air and is thus able to clean contaminated water or polluted air. should, in principle, only be loaded with low-turbidity water (e.g. < 0.2 NTU, Nephelometric Turbidity Units). The effect of the water temperature on the adsorptionThe accumulation of gaseous or liquid substances on the surface of a solid. of natural, organic substances in water is relatively minor. High DOC concentrations in untreated water can limit the activated carbon’s adsorption capacity for trace elements, which should therefore be minimised as much as possible by other means prior to the adsorption. Although granulated iron hydroxide is very effective in the removal of arsenic, its ability to eliminate dissolved organic substances is quite limited.

Cost factors in industrialised, emerging and developing countries (Gieb, 2005)

Drinking water disinfection is the most important and frequently employed treatment process throughout the world. As a rule, drinking water purification outside Germany stipulates the disinfection of the water and its subsequent introduction to the distribution network with free disinfectant; this is often a necessity given the fact that conditions in the distribution network are frequently less than ideal. Since a residual chlorine level is desired at the water tap, appropriate disinfectants with a lasting depot effect are still required as a final safety step following the optimisation of the water treatment process. However, care must be taken to avoid overdosage due to the potential for disinfectant by-product formation and negative reactions on the part of consumers.

Water quality and corrosion in pipe networks

Outside Germany, the impact of water quality on pipe corrosion cannot be adequately assessed by the common-practice method of establishing the corrosion probability on the basis of ion ratios. More concrete information can be gained by conducting additional experiments with a special test rig (see photo) under the applicable specific conditions.

When assessing the basic applicability of the various procedures from a technical perspective, the country-specific conditions regarding infrastructure, availability etc. must be taken into account (see table). Provided that any climatic differences are taken into account, transferring these procedures to other industrialised countries does not represent a problem, since a virtually identical technological standard can be assumed. However, this does not apply to developing and emerging countries (or only to a limited extent).

The results of the joint project have been published in the form of guidelines, while an accompanying CD documents the final reports of the sub-projects: “Export-oriented R&D in the field of water supply and wastewater treatment.
Part I: Drinking water, volume 2: Guidelines, in-house publication of DVGW Water Technology Centre Karlsruhe (2006), ISBN: 3-00-015478-7” (out of print)

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2.4.04 Adapted wastewater technologies

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2.4.02 Adapted slow filtration