INTRODUCTION

The use of sewage plants for smaller developments such as hotels, hostels, lodges, prisons etc has been internationally accepted as the standard installation, if no connection to a main sewage system is available.

The use of sewage plants for individual houses has been accepted in some of the more environmental aware countries worldwide and should be considered by authorities and individuals worldwide. In some areas septic tanks are no longer permitted, due to their contribution to ground water and river pollution.

SIYAGEZA as part of their wide range of sewage plants now offers a small plant, which incorporates all portions of a full sewage plant in a single unit, which can easily be installed and maintained by a household.

This new development does offer new opportunity to keep our environment safe for future generations. The effluent of this plant is suitable for discharge, unlike septic tanks, which remove only one third of the pollutants.

Do not experience problems of smell due to bad soak away of septic tank effluent in areas where the water table is high or where there is high clay content in the soil.

SEWAGE PLANT TECHNOLOGY

The basic technology used in the single household units is identical to large sewage plants being the activated sludge process.

The activated sludge process is a natural process and nature offers us a unique solution to treat sewage. Nature has provided a special balance in this process in that the microorganisms with the assistance of oxygen will breakdown the BOD levels to acceptable levels.
With the use of a correctly designed settler it is possible to remove the solid particles and generate a clean effluent.

In the activated sludge process, we identify four major sections:
1. Collection and anaerobic storage
2. Aeration of the sludge
3. Settling of the sludge removing all solids
4. Chlorination and phosphor removal to bring the final effluent up to the required standard.

The FMPX plant incorporates all of these aspects in one tank.

The activated sludge system has definite advantages over other competitive systems such as rotary disc systems marketed internationally. Some of the advantages are:
· Less maintenance as the mechanical equipment of the activated sludge is limited to a standard fan, which requires no maintenance.
· Less volume required, as no additional septic tank or storage tank is required. The activated sludge is a balanced system that can accommodate fluctuations in flow.
· The rotary disc requires special supports often resulting in much higher civil costs.

The plants will produce an effluent in accordance with international standard excluding special standards where phosphate removal is required.
BOD : less than 35 mg/l
Ammonia : less than 3 mg/l
Nitrates : less than 10 mg/l

FMPX PLANT - MORE DETAILED DESCRIPTION

The four sections described above are clearly visible in the construction of the FMPX unit. A typical plant is shown on the figure above:

1. A collection / interceptor section: this section allows the collection of the settled solids, two policies of sludge removal are possible. A special system of sludge concentration is available for the removal of sludge after a few months. Alternatively the plant can be equipped with a hand pump for the weekly removal of sludge. This sludge can be pumped out and distributed over a garden.

2. The aeration section has a special aeration ring positioned in the bottom of the tank. Air is introduced and by means of the special aeration system, intimate contact is established between the air and the solid matter. The fan is installed on top of the vessel keeping the plant compact.

3. The third section of the plant consists of a settler tank where solids are settled and a clear overflow liquid is produced. Although more expensive to manufacture, we only use conical tanks for the settler so that no solids can collect in the bottom of the tank. If these solids are not returned to the process, they would become anaerobic and cause foaming in the settler, generating a dirty effluent.

4. The final section is the chlorine contact section, which finally treats the liquor to produce an effluent in accordance with the above Standard suitable for discharge into rivers or for use as irrigation.
Chlorination is done using standard chlorine pills, and a hand hole is supplied to make replacement easy.

It is clear from the above that the basic process used in the FMPX plants is basic and simple. For the evaluation of any system, it is imperative that the operation of such a plant is also simple and does not require special equipment or specialised operators.

The sludge collected in the settler has to be recycled back into the main process. The use of pumps would require special operating skills and will generate high maintenance costs. The FMP system uses a special airlift system, so that the fan is the only moving part on the plant. The complete system is thus easy to operate and requires no special skills to maintain.

To ensure the complete plant offers the user a long-term viable alternative two more requirements are to be met:

a. The plant must withstand the corrosive nature of sewage. This ensures that the life of the plant is extended as far as possible without replacement or repairs.
b. The plant must remain economically viable.

This is accomplished by the use of a Polypropylene construction. The construction is also light and easy to install.

OPERATION

Operation of the FMPX plant is extremely easy and requires no special training.

All that is required is the following:

- Ensure that the fan is running. It should be noted however that if the fan is left off for a period of time, the plant may generate a smell for a few days but will find its own equilibrium very quickly, without any special operations. This is in stark contrast with many rotary disc designs, where unbalanced discs can cause serious operational problems.

- Remove the sludge from time to time: with a sludge concentration system, a sightglass is included to allow the operator to see that sludge levels are reached and desludging is required. A manhole is provided for the removal of the sludge. In case of installation of a sludge pump, the operator has to remove some sludge on a weekly (or two weekly) basis removing the excess sludge.

- Maintenance : the plant is maintenance free as the only rotary equipment is the fan, which is designed for a bearing life of over five years. The fan supplied is quiet and spares are available worldwide, if ever required.

CONCLUSION

The above system offers a solution to any household, producing a safe environmentally friendly effluent at a reasonable cost and extremely low operational cost.