Saturday, 8 November 2008

Low-cost sewerage in the Nile Delta

This week I’ve been asked to look at low-cost sewerage schemes in two small villages in the Governorate of Kafr El Sheikh in the Nile Delta in Egypt (populations <5000). This is a GTZ-funded project on decentralized wastewater management, executed by Rodeco, a firm of German consulting engineers (details also here), and Aldar Consulting Engineers, Cairo. One village, El Mofty El Kobra, has had settled sewerage since February 2005 and the other, Om Sen, has had simplified sewerage since November 2007. In both villages the wastewater is pumped from the village a short distance and then treated in waste stabilization ponds. The capital costs were covered by funds from GTZ and the Egyptian Fund for Social Development.

Apart from the different forms of sewerage, the solutions adopted for the two villages (and several others not yet commissioned) were essentially identical. Each village had to form a Community Development Association which first of all had to raise from the village households the money required for the waste stabilization ponds (about 1½ feddans or 0.63 ha). Once the system was commissioned the CDA assumed ownership of the whole system and responsibility for its operation and maintenance (collection and treatment) − it does this by (a) collecting a monthly fee of EGP 10 (USD 1.83) from each household and (b) contracting a local contractor to do the actual O&M of the system, including in the case of El Mofty El Kobra annual desludging of the solids interceptor tanks. The monthly fee of EGP 10 represents a huge financial benefit to the village households as before the project they were each paying EGP 25−30 per month to have their ‘septic tanks’ (really cess pits) emptied − so they now pay much less for a much improved wastewater management system. Both villages have a healthy surplus in their CDA bank accounts.

There have been very few problems and both WSP systems produce effluents compliant with Egyptian standards for village wastewaters (<60 mg BOD/l, <50 mg suspended solids/l and <3000 faecal coliforms /100 ml). The one major problem was the villagers discharging animal manure into the sewer system − they thought this was a convenient method of disposal, not realising the hugely adverse effect it would have on the wastewater treatment plant (the BOD increased by about ten times!). The problem was solved (more or less, anyway) by (a) explaining to them why they shouldn’t dispose of animal manure in the sewers and (b) by the CDA fining them if they did − the fine is very large (EGP 400 for the first offence, EGP 1000 for repeat offences), so very few households now put animal manure in the sewers.

Water consumption has increased from <40 litres per person per day to ~80−90 lpd as, prior to the project, all households made a real effort to keep consumption low in order to avoid having to pay for their ‘septic tank’ to be emptied more than once a month. Now there is no such requirement and they use as much water as they need − indeed quite a few households now enjoy the status of having washing machines!

The engineering aspects of the project are quite straightforward (correct design of the sewer system, pumping station and the ponds) and account for only about 20% of the consulting engineers’ time. The remaining 80% of their time is spent on social aspects of the system: activating, developing and supporting the CDAs, which need to understand how the system works, how it should be operated and maintained, how to bank the money collected each month from the village households, and how to contract and supervise the O&M contractor. The evidence so far is that the CDAs are performing very well.

The USD 201 million World Bank project ‘Egypt − Integrated Sanitation and Sewerage Infrastructure Project’ (Project Appraisal Document here, Project Information Document here) will extend this work on decentralized wastewater management. So in the none too distant future the wastewater management models developed in El Mofty El Kobra and Om Sen will be replicated many times over, which can only be good news for Nile Delta villagers.