Sustainable Concepts Towards a
Zero Outflow Municipality

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•  Introduction

The SEKEM farm is producing natural drugs by growing various herbs and extracting the active substances from them by an industrial cycle that ends up in the final products. It's a community, a few hundred people are living and working there, and there's also a school for about 500 students.

The target area for the pilot project comprises the school of the farm, a few buildings, the campus kitchen and a laundry room. The wastewater is composed of 100 % domestic wastewater.

In the past the wastewater was treated in a hybrid constructed wetland, comprising a primary treatment and a sequence of vertical filter (VF) +horizontal filter (HF) + storage tank. In a former time the effluent contained in the storage tank was pumped to fields for irrigating.

At the moment, the vertical flow CW is clogged due to massive under sizing. The whole treatment system is by-passed. The raw wastewater is used for irrigation, being pumped directly from the septic tank to the fields. The septic tank itself is in dire condition.

The pilot activity mainly aims at demonstrating a sustainable, working and low-cost wastewater treatment as suggested by Zer0-M, which shall prove that these solutions work under real conditions and ultimately allow the further spreading of the demonstrated technique. The pilot activity will also help to gain experience with the constructed wetland and sludge drying reed bed implemented under real conditions and the Egyptian climate. It will help to improve them if necessary until they can be recommended for wide use.

Last but not least the wastewater treatment plant shall allow the treatment and safe reuse of the wastewater produced by part of the SEKEM farm for irrigation purposes. It is part of the overall water, and environmental, strategy of SEKEM. Presently a next stage is under preparation which will deal with water from vegetable and herb processing facilities and a small settlement, the waters of which are mixed at present, roughly treated and reused for minor purposes (irrigation of a fuel wood plantation) because of its poor quality. If the present example is successful further similar systems will be implemented, which are already under discussion, for villages located around the farm.

The high profile of SEKEM (http://www.sekem.com) throughout Egypt and the reputation of its founder, Dr. Ibrahim Abouleish, will give the pilots a high visibility in Egypt.

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•  Activities

The Zer0-M project therefore suggests the design described below for a pilot wastewater treatment plant as a solution for an efficient wastewater treatment.

The intention of the plant is to increase the available water for agricultural purposes and at the same time solve the problem of uncontrolled wastewater disposal in the targeted area. A “sludge treatment constructed wetland” for treating and composting the sludge allows the reuse of the nutrients as high quality fertiliser on the farm.

Some of the troubles, which occurred in the present treatment system, are due to a lack of maintenance of the mechanical components (e.g. pumps). For this reason it seems advisable to design a robust system, as “simple” and “low-tech” as possible.

Table 1 : The suggested design for the pilot treatment plant consists of:

The provided works on the plant will include civil, electro-mechanical works and supplies (piping system, pumps, valves).

It's planned to reuse and adapt some parts of the existing decommissioned treatment plant. The structures are not in very good condition. These parts have to be extensively renovated and adapted to the new applications.

It also seemed useful to renovate the old storage pond. The existing vertical filter (VF) +horizontal filter (HF) of the existing treatment plant could be adapted for the sludge and leachate treatment constructed wetland.

The condition of the existing septic tank makes any further use impossible. For security reasons the construction has to be backfilled.

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•  Dimensioning Criteria

The present wastewater production in the target area is about 15 m³ per day. Because of the constant increase of the population in the last few years an additional flow of 5 m³/d shall be taken into consideration for the dimensioning of the components of the plant.

Actual design flow rate:

The farm having extension plans for the served area, which are not yet 100 % sure, the possibility to extend the wastewater treatment by 50% of the present design flow to a stage 2 was taken into consideration. Where an easy extension of components is possible, space shall be provided for such an extension otherwise the extended flow of stage 2 is considered the design flow.

To immediately base the design on the increased design flow and implement the larger constructed wetland would mainly lead to higher evapo-transpiration losses. The construction of stage II is not useful for the actual flow rate (15m³/d).

Construction of the extension stage (stage II):

The pre-treatment cannot be easily increased and will therefore be dimensioned for the higher flow rate of 30 m³/d (Stage II – extension stage).

The biological stage of the plant can easily be increased without any construction changes to the presently implemented treatment plant by adding a 2 nd horizontal flow wetland on the prepared extension area.