Iwa international Specialist Conference

REFERENCES

Å. Svärd, C. Gruvberger, H. Aspegren, J. la Cour Jansen, T. H. Christensen (2002). Pilot scale digestion of source-sorted household waste as a tool for evaluation of different pre-sorting and pre-treatment strategies. To be presented at the 3rd International symposium on Anaerobic Digestion of Solid Wastes, Munich 18-20 September 2002 Germany.
Gruvberger, C., Aspegren, H., Andersson, B. and la Cour Jansen, J. (2002) Sustainability Concept for a Newly Built Urban Area in Malmö, Sweden. Presented at the 3rd IWA World Water Congress, 7-12 April 2002, Melbourne, Australia.

82.

Performance of Wastewater Treatment Plants in the Gaza, Potential use of Wastewater and Sludge in agriculture

B. H. Shomar*, G. Müller, A. Yahya

Institute of Environmental Geochemistry, University of Heidelberg,

Im Neuenheimer Feld 236, 69120 Heidelberg, Germany.

Abstract

In three sampling campaigns during the period of November 2000 to June 2002, 41 industrial wastewater samples, 120 domestic wastewater samples and 35 sludge samples were collected from the Gaza Strip. It is objective of this study to highlight the performance of the existing wastewater treatment plants in Gaza; moreover, it aims to introduce for the first time the heavy metal contents and some parameters in the industrial wastewater effluents, influent and effluent of domestic wastewater and sludge; and finally the various options that aim to reuse the treated wastewater and sludge in the Gaza Strip in a manner that will insure sustainable development.

Twelve elements (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were analyzed in 150 composite samples of influent and effluent wastewater; the results revealed that domestic wastewater influent contains considerable amounts of heavy metals and the treatment plants of Gaza are able to remove 40-70% of most metals during the treatment process. Heavy metals in industrial wastewater effluent are within the ranges of national and international standards. All industries of Gaza are light; and although they have no treatment facilities, their effluents are being discharged to municipal sewerage system and the existing treatment plants are capable to absorb the industrial effluents with no significant impact on treatment bioprocesses.

Thirty parameters were determined in sludge samples; P, AOX, C, S, CaCO₃, Mg, Ca, Na, K, Li, Cu, Zn, Ni, Pb, Mn, Fe, Cr, Co, Cd, As, Hg, Ti, Se, Br, Rb, Th, Sr, Y, U, and Zr. Although there are no treatment facilities for sludge within the treatment plants, the results indicated that the sludge in general is clean of heavy metals. The FAAS results showed that only Zn in 95% of sludge samples is more than 2000 mg/kg which exceeds the standards of all industrial countries of sludge to be applied on agricultural land, while the EMMA result of Zn was 1400 mg/kg which is equal to the highest American standard. AOX as well in few samples of both treatment plants is more than 500 mg Cl/kg which is more than the German and the EU standards of sludge to be used in land application. The site visits revealed that the main sources of AOX are expected to be the 26 paper industries distributed in Gaza and northern area. These industries are using old technologies and they represent the largest consumer of chlorine and the greatest source of toxic organochlorine discharges directly into waterways.

The severe shortage in water resources in Gaza enhances the reuse of treated wastewater in agriculture and the results obtained in this study encourage this proposal to come true. The sludge, on the other hand, needs to be improved from the Zn and the AOX point of view; however further studies on microbiology and the virology are needed. Scientific attempts should be taken to match the metal inputs from sludge to soil with the small annual losses of metals due to crop removal, soil erosion, and leaching, so the metal concentrations do not exceed background levels. Moreover, further step is to be taken; to perform a risk assessment to determine what heavy metal contamination levels represent an acceptable risk.

83.

Municipal sludge as a resource in urban green areas

Arne Sæbø* and Trond Knapp Haraldsen**

* The Norwegian Crop Research Institute, Særheim Research Centre, 4353 KLEPP,

** The Norwegian Centre for Soil and Environmental Research, N-1432 Ås, Norway

The interest for use of municipal sludge in urban green areas is increasing. One reason is the ambivalent attitude to the use of municipal sludge in soils for food production. Another, and in this context a more relevant reason, is that the green area sector is often struggling with low quality soils for the growing medium. In mixtures of sand and peat, which is often used in Norway, the plants will suffer from a lack of major plant nutrients and show poor growth unless the soils receive sufficient amounts of fertilizer. Municipal sludge represents a type of organic waste, which has a variable content of plant nutrients and heavy metals. Incorporation of sludge with available plant nutrients may considerably increase the quality of the growing medias for high value trees and shrubs, as well as for herbs and grasses.
Experiments were started at six locations in Norway, to study the effect of different types of municipal sludge in urban green areas with trees, shrubs and turf grass. The sludge products used in the experiment were processed by different technologies, causing differences in dry matter contents and content and availability of plant nutrients. So far, there were large differences between the sludge products in how user friendly they are and how well they support plant establishment and growth. Products with a high dry matter content were easy to handle and incorporate in the soil, but showed a slow release of plant nutrients during establishment. Products with low dry matter content were more difficult to incorporate evenly in the soil, but had a more rapid release of plant nutrients. Norwegian regulations for use of municipal sludge allow a layer of five cm of sludge to be incorporated in soils at green areas. Maximum allowed amounts often supply much more plant nutrients than the need of the plants, and may cause enhanced or inhibited growth. In order to promote the use of large quantities of municipal sludge to green areas, the sludge producers should emphasise the product’s properties and quality. Documentation, on how large amounts of the products that can be used in green areas, needs to be provided. The end users of the products need to feel comfortable with the use of the products and they must see the benefits in the establishment and management of green areas.
In the presentation, the properties of sludge products for the planners and practitioners of urban green areas will be discussed. The preliminary observations of different sludge products on turf grass and on the establishment of trees and shrubs will be presented.

84.

Induced magnesium ammonia phosphate precipitation to prevent incrustations in the sludge chain of the wastewater treatment plant Waßmannsdorf
Bernd Heinzmann, Berliner Wasser Betriebe