Sustainable Development Success Stories

Cairo sludge disposal study

Location Cairo, Egypt.
Responsible Organisation National Research Centre in partnership with WRc plc., European Investment Bank and Cairo Wastewater Organisation.
Description Wastewater treatment is an essential component of clean freshwater, in that the former prevents the discharge of pollutants and disease agents to the latter. Sludge, also known as biosolids, is the primarily organic residue left from wastewater treatment. The implementation of wastewater projects in the major cities of Egypt will result in large quantities of biosolids being produced and requiring disposal. The Greater Cairo Wastewater Project will result in about 0.4 million tons of dry solids per year within the next decade. The Cairo Sludge Disposal Study was initiated under the Mediterranean Environmental Technical Assistance Programme, funded by the European Investment Bank and promoted by the Cairo Wastewater Organisation, to resolve at least part of the difficult problem of biosolids disposal in the Cairo area. The study began in July 1995 and comprises three phases over 42 months. Phase 1 was a review and planning stage, and Phase 2 includes biosolids sampling and field trial programs. A practical guide to the use of biosolids, the structure of an organisation for undertaking the operational implementation of biosolids reuse in agriculture, and a master plan will be developed based on the practical results obtained.
Issues Addressed Freshwater, Science, Capacity Building, Technology Transfer.
Results Achieved Seven trial sites were established, including a site owned by Ain Shams University and several private farms. At each site, several coordinated arable crop or fruit production trials have been installed, and these will continue over three years. Different types of biosolids from Cairo wastewater treatment plants are being used, including anaerobically digested and composted materials. About 150 acres of test sites have been established. The trials include detailed statistical, multi-factor designs aimed at elucidating the fertiliser values of different types of biosolids in different cropping situations. Larger trials demonstrate the practicality and value of using biosolids. Each trial is monitored for crop production and quality, including nutrient efficiency and uptake of heavy metals.

Interim conclusions are: biosolids had an especially beneficial effect on wheat, berseem, forage maize, and grape vine; digested biosolids appear to offer significant nitrogen fertiliser replacement value to farmers; no harmful effects of biosolids on crops have been detected in field trials; and the benefits of spreading biosolids on newly reclaimed soils are expected to increase with cumulative applications to enhance soil fertility. All the data from the trials and the biosolids sampling programs will contribute to the development of agricultural extension information to be used during the operational implementation of biosolids reuse in agriculture. The data will also contribute to the scientific basis for regulating biosolids reuse, which is urgently required. Effective operational and environmental controls and well-informed farmers are the essentials for safe, sustainable biosolids reuse programmes.

Lessons Learned The study will prepare a master plan for biosolids reuse in the Greater Cairo area, taking into account the results of the trials, biosolids quality, farm practices, distances, etc. Despite very large quantities of biosolids to be produced in the future, the area of land required annually will be a very small proportion of potentially available land. Farmers in Egypt are prepared to pay for biosolids due to the regional scarcity of traditional manure and rapidly increasing costs of inorganic fertilisers. Consequently, a biosolids reuse program could recover some of its operating costs. The Cairo Sludge Disposal Study can be viewed as a model for other towns and cities in Egypt and in other countries, where rapidly expanding urban populations and the installation of wastewater collection and treatment facilities will inevitably result in the production of significant quantities of biosolids. Biosolids require cost-effective, environmentally acceptable, and sustainable disposal, and recycling to agricultural land is widely considered to be the best practicable environmental option. Effective regulation and public education, however, must secure this option.
Contact Mr. Jeremy E. Hall, WRc plc
Henley Road, Medmenham, Marlow
Buckinghamshire SL7 2HD, United Kingdom
Tel. (44 1) 4915 71531; Fax (44 1) 4915 79094
E-mail hall_j@wrcpk.co.uk

Mr. Abd El Rasheed Shehata
National Research Centre
Cairo, Egypt.