Installation and Operating
Guidelines
for the
“GEM” Mini Sewage Treatment
Plant
A Sewage Plant is not
the end of the line, but
the beginning of good
health for all life.
African Environmental Development
Portion 129 of the farm
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Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
Environmental
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“GEM” Mini Sewage Treatment Plant Installation and
Operating Guidelines
Congratulations on your purchase of the “GEM” Mini Sewage Treatment
Plant. In doing so, you have joined the ever increasing community of
concerned citizens who care for their environment.
In essence, the “GEM” Mini Sewage Treatment Plant is a compact sewage
treatment plant employing principles of anaerobic and aerobic (activated
sludge) biological sewage treatment, used by all municipal sewage treatment
plants in South Africa. The “GEM” Mini Sewage Treatment Plant is merely a
miniature version of a municipal sewage treatment plant and is scaled down to
suit the demands of a single household.
The “GEM” Mini Sewage Treatment Plant is ideally suited for areas where the
soil and/or geological formations exclude the use of French drains due to the
potential risk of groundwater contamination or sinkhole formation or in
environmentally sensitive areas such as the Cradle of Humankind World
Heritage Site, located almost exclusively on dolomitic limestone. The unit is
designed for a normal household of up to 6 people (calculated at a hydraulic
load of 200 litres per person per day).
Item List
Upon purchase of the “GEM” Mini Sewage Treatment Plant, you will receive
the following items. Please refer to Figure 1 for details:
1. One x 2-compartment Poly Rib anaerobic tank complete with manhole
and manhole lid, 110mm inlet, inlet inspection eye with screw-on cap
and all pipes and fittings to connect to the secondary aerobic tank.
2. One x Poly Rib aerobic and settling tank combination, complete with
manhole and manhole lid, 110mm inlet from anaerobic tank, 50mm
sludge outlet to anaerobic tank, 110mm outlet to chlorinator with
inspection eye, settling tank incorporated into the unit with 50mm airlift
pump and controls to regulate the return activated sludge. Also
included in this tank is an aeration mat with perforated stainless steel
aerator and the air inlet from the blower and all piping and regulating
valves, to control the flow to the airlift pump and aeration mat.
3. One 110mm interconnecting pipe to connect the two tanks together.
4. One 110mm to 50mm reducer for installation at the outlet of the aerobic
tank.
5. 1 chlorinator to be installed in the 50mm effluent line after the aerobic
tank.
6. 1 air blower.
7. 0ne 50mm socket to connect the 50mm pipes from both tanks together
in the centre of the installation.
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African Environmental Development
Portion 129 of the farm
Sterkfontein 173 IQ
Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
Environmental
Development
Figure 1 – General layout of the “GEM” Mini Sewage Treatment Plant
Installing the “GEM” Mini Sewage Treatment Plant
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Excavate a hole in the ground 1.5m wide and
approximately 4.5m in length. This will allow half a
metre working space at each end of the installation
and half a metre between the two tanks. The depth of
the excavation will depend on the elevation of the
sewage pipe at the entrance of the installation but
should ideally not exceed 1.4m. Ideally, the two lids of
the manholes should extend above ground level, but
in such cases where the fall of ground is very low,
Figure 2 – Manhole
manhole lid extensions are available to extend the lids lid extension
by approximately 500mm.
Level and compact the bottom of the excavation. Cast a level, 75mm
thick concrete slab at the bottom of the hole. It is very important for the
operation of the system for the two tanks to be installed 100% level.
Once the concrete has cured, place the two tanks in the hole on the
concrete slab. Refer Figure 1 for the order and direction of the tanks.
Use silicone grease or dishwashing liquid and coat the 110mm
interconnecting pipe with the liquid. Insert it into the hole of the one
tank. The holes in the centre of each tank are fitted with rubber gaskets
into which this interconnecting pipe can be pushed.
Apply PVC glue to the end of one of the white 50mm pipes, which
should now be facing each other in the centre of the installation, and
push the 50mm socket over the 50mm pipe.
Carefully move the two tanks closer together and insert the other end
of the 110mm interconnecting pipe into the hole in the centre of the
other tank using ample silicone grease or dishwashing liquid to
facilitate the operation.
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Republic of South Africa
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African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
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Once the interconnecting pipe has been inserted into the openings of
both tanks, move the tanks closer together until the socket, which you
have glued onto the one 50mm pipe, is near its matching pipe
protruding from the other tank. Apply PVC glue to the end of this other
50mm pipe and push the two tanks further together until the socket
engages into the other 50mm pipe. Refer to Figure 1 for details as to
how the installation should look when the two tanks are together.
The interconnecting pipe is provided with a black ring. Move the
interconnecting pipe either way until the black ring is in the centre in
between the two tanks. (Refer Figure 1)
Connect the 110mm sewer from the homestead onto the 110mm inlet
of the anaerobic tank. Your plumbing contractor normally does this.
In order to prevent soil from entering either of the tanks, place the lids
on both the manholes and place a plastic bag temporarily over the
110mm outlet of the aerobic tank and commence backfilling. It is
important that the excavation be backfilled and compacter thoroughly.
The tanks are designed to handle considerable pressure from outside
(resistant to implosion), but will concertina outwards when filled with
water and not supported properly on the outside. Take particular care
that the openings underneath the tanks, either side of the bases of the
tanks, are filled in thoroughly. As you fill in
and compact, you may fill the tanks with
clean water. Do this progressively and
ensure that the water level never exceeds
the level of well-compacted soil on the
outside of the tanks. Do not initially fill the
tanks more than two thirds. Alternatively,
Figure 3 – 110mm socket
backfill the excavation entirely before and 110 to 50mm reducer
putting water into the tanks.
Once the excavation has been backfilled, push the 110mm socket over
the outlet of the aerobic tank (using silicone grease or dishwashing
liquid to facilitate the operation). The
socket is fitted with a rubber gasket
and will seal perfectly.
Glue the 110 to 50mm reducer into the
open end of the socket using PVC
glue.
Cut a length of 50mm PVC pipe
(100mm will do, but any length will be
OK). Insert the one end of the pipe into
Figure 4 - Chlorinator
the 50mm end of the 110 to 50mm
reducer. This end is also fitted with a
rubber seal. Use silicone grease or dishwashing liquid to facilitate the
operation.
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Portion 129 of the farm
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African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
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Apply PVC glue onto the other end of the length of pipe and insert one
of the sockets of the chlorinator onto the pipe, keeping the chlorinator
in an upright position.
Glue another length of 50mm pipe onto the
other end of the chlorinator. Depending on the
distance from the chlorinator to the point of
discharge of the final effluent, either white
50mm PVC waste pipe can be used or black
50mm irrigation hose. The latter is much
cheaper, more flexible and, as it has a inside
diameter of 50mm opposed to the outside Figure 5 – Chlorinator
diameter 50mm of the white PVC waste pipe, installed in manhole
it will fit perfectly over the waste pipe and will
only require a hose clamp to hold it in place.
Once installed, the chlorinator should be protected by constructing
some sort of a manhole around it. Figure 5 shows one of the ways the
chlorinator can be protected. Always keep in mind that the cartridge in
the chlorinator needs to be replaced regularly and that the protection
around the chlorinator does not hinder this operation.
If there is not a cartridge in the chlorinator, place one in the chlorinator
and screw the dark-grey cap all the way down onto the chlorinator. The
deeper the cap is screwed down, the higher the dose of chlorine. For
our purposes, however, it is recommended to screw the cap down all
the way. At this dosage rate, the chlorine cartridge should last around 4
months.
Fill the tanks completely with clean water, to
the point where it starts overflowing through
the chlorinator.
The next step is to connect the air blower.
The blower does not have to be installed on
site, but could be installed some distance
away from the plant. It is recommended that
the blower be installed in the garage of the
Figure 6 – Air blower
homestead and that the air be piped to the
plant using an ordinary 12mm garden hose for
this purpose. The hose can be buried in the same trench as the main
sewer from the homestead. Take care when laying the hose and
backfilling the trench that the hose is not pinched or twisted. The
blower does produce a lot of heat and should be installed in a wellventilated area. Never place it closer than 100mm from any wall. If the
blower is installed outside near the plant, it should be protected against
rain and be well ventilated. Do, however, not place it in an enclosed
area such as the fibreglass enclosures made for swimming pool
pumps. The blower produces too much heat and will overheat.
Connect the blower to a standard 220 Volt 3-point outlet.
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Portion 129 of the farm
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Republic of South Africa
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African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
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Connect the other end of the hose to the flexible 12mm silicone pipe
protruding from the aerobic tank.
Ensure that the aeration mat is lying flat
on the bottom of the aerobic tank with the
stainless steel pipe facing to the top.
Turn the power of blower on and adjust
the air feed as described in the following
section.
Level the ground around the installation
and remove all unnecessary items lying
Figure 7 – Aeration mat
around. For further protection, especially if
you have heavy animals, such as horses
and cattle, which may wander over the installation, construct a concrete
slab or install cement paving over the plant. The plant has adequate
strength to withstand normal human traffic without requiring additional
support.
Figure 8 – An example of a plant after installation. All that is visible of the plant itself are the
two manhole lids and an inspection eye in the foreground. In the background is a 3m holding
dam with fountain from where the effluent water is irrigated.
For all practical purposes, the installation of the “GEM” Mini Sewage
Treatment Plant is now complete.
If this plant is being installed at a new homestead, do not connect the sewer to
the plant until all contractors have left the building site. Contractors are
notorious for washing all types of items down the drain, including paint,
cement, rags, Cement bags, sand and any other type of building by-product.
Give the sewer a thorough flushing before connecting it to the sewage plant.
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African Environmental Development
Portion 129 of the farm
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Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
Environmental
Development
Operating the “GEM” Mini Sewage Treatment Plant
The “GEM” Mini Sewage Treatment Plant is made to be as maintenance-free
as possible. There are only a few things that require periodic attention.
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When the plant is installed for
the first time, it will be filled with
clean water. While the water is
still transparent, turn on the
power of the blower and check if
air is bubbling from the aeration
mat as well as from the airlift
pump. Air from the airlift pump,
together with the water it will be
Figure 9 – The 50mm return activated
pumping, should be visible sludge pipe with 30mm holes and the air
through the three 30mm holes in controls inside the aerobic tank.
the 50mm return activated
sludge pipe in the aeration tank. A rule of thumb is to adjust the air
valves in such a manner that almost all the air is channelled to the
aeration mat with only enough air to the airlift pump to produce a water
flow over all three of the 30mm holes, with only a trickle of water
flowing past the 3 holes to the anaerobic tank. Once adjusted correctly,
these settings should be left alone. Now the aerobic section is being
aerated while water is pumped from the bottom of the settling section
back to the aerobic section. Once the plant is commissioned, the airlift
pump will be pumping activated sludge flocks that have settled to the
bottom of the settling area back to the aerobic area via the three holes
in the return activated sludge pipe.
After an extended period of operation, the population of activated
sludge bacteria may increase to unacceptably high numbers. This is
usually visible as a thick dark-brown “soup” in the aerobic section.
When this happens, the black pipe surrounding the holes in the 50mm
return activated sludge pipe should be turned through 90° to close the
3 holes for a period of approximately 30 min. to 1 hour. During this
period the activated sludge will be returned to the anaerobic tank,
where the anaerobic bacteria occupying this tank will consume it.
Remember to open the 3 holes in the return activated sludge pipe after
this operation.
There is no need to inoculate the system. There are enough bacteria in
human faeces to perform this function. Also keep in mind that the
population of bacteria will gradually build up in the system. Do not
expect perfect effluent within the first two months. After a while, the
effluent water quality will stabilise and will become a non-offensive
water source, which can be used quite safely for irrigation purposes as,
discussed later on in this document.
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African Environmental Development
Portion 129 of the farm
Sterkfontein 173 IQ
Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
Environmental
Development
Maintenance of the “GEM” Mini Sewage Treatment Plant
Although we attempted to make the “GEM” Mini Sewage Treatment Plant as
maintenance free as possible, periodic maintenance will be required. Please
adhere to the following maintenance procedures:
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Check the plant on a weekly basis. Open the anaerobic tank’s manhole
lid and check that not more than a trickle of water is coming through
from the aerobic tank’s return activated sludge pipe. If no water is being
returned, adjust the air controls as described in the above section
under the heading: “Operating the “GEM” Mini Sewage Treatment
Plant”. After some months of operation, a thick scum layer will develop
on the surface of the primary section of the anaerobic tank. Do not
attempt to break this layer as it forms an effective barrier, which
excludes oxygen from the water underneath it.
On a monthly basis, use a thin stick to measure the amount of nonbiodegradable sediment, which will accumulate at the bottom of the
primary section of the anaerobic tank. The accumulation of sediment in
this tank will be governed by the amount of non-biodegradable matter
that is washed down the drain. Non-biodegradable matter will include
things such as sand, plastic, gravel, etc. from washing of clothes,
vegetables, etc. When measuring the sediment layer, try not to upset
the scum layer on the surface of the water too much. When the
sediment fills up approximately one third of the tank, it is time to get a
septic tank cleaning specialist to vacuum out the anaerobic tank.
Depending on the amount of non-biodegradable matter present in your
sewage, this will take between 5 and 15+ years to occur. Under normal
circumstances, it will never be necessary to vacuum out the aerobic
tank.
Observe the amount of fat and grease build-up in the first section of the
anaerobic tank. Under normal circumstances, a sand trap or grease
trap is not fitted ahead of the plant. Under conditions where there may
be excessive grease or sand/gravel entering the plant, it is
recommended to install these in order to protect the plant from
premature siltation.
Open the aerobic tank lid. Observe the amount of air from the aeration
mat and from the airlift pump. Adjust, if necessary, as described in the
section here above under the heading: “Operating the “GEM” Mini
Sewage Treatment Plant”. If you are not able to adjust the air to the
aeration mat satisfactorily, there may be another problem. This could
either be an air leak between the blower and the plant (moles
sometimes burrow/chew right through hosepipes!) or a problem with
the blower. Sometimes in areas served by calcium-rich borehole water,
the holes in the aeration mat will become blocked with calcium
carbonate scale over a very long time. In this case, the aeration mat
can be lifted out of the tank by its flexible silicone hose. Under these
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African Environmental Development
Portion 129 of the farm
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Republic of South Africa
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African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
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Development
conditions, it is recommended to soak the aeration mat overnight in
vinegar or a diluted pool acid solution. This will remove any scale and
render the aeration mat as good as new. Replace the mat back in the
aerobic tank.
Using a small stick, dislodge any bacterial growth that may form around
and inside of the 3 holes in the return activated sludge pipe. It is a
normal occurrence for bacteria to grow on these surfaces. If let alone,
they will eventually block the holes entirely.
Inspect the chlorine cartridge on a weekly basis by unscrewing the lid
on the chlorinator and replace the cartridge when empty. Under normal
circumstances, the cartridge should last up to 4 months. Replacement
cartridges are available from Control Chemicals (Pty) Ltd, 70
13th Road, Kew, Johannesburg, Tel: 011 786-7166/9, Fax: 011 8851300.
Inspect the blower on a very regular basis. It is fitted with a small filter
at its inlet. Under the dusty African conditions experienced on the
Highveld and in other areas of South Africa, this filter will block within 3
to 6 months. The filter used is an inexpensive filter obtainable from any
motorcar spares or hypermarket outlet. Ensure that the blower is not
covered and that the fan blowing air over the motor is not covered or
obstructed in any way.
Operating Principles of the “GEM” Mini Sewage Treatment Plant
The “GEM” Mini Sewage Treatment Plant makes use of natural biological
processes to purify the sewage water and it does this in three stages.
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The First Stage (Anaerobic Digestion)
The first stage of the plant makes use of anaerobic bacteria to break
down the complex organic material in the sewage to simpler organic
molecules. This phase is similar to a septic tank where anaerobic
bacteria (bacteria that live in the absence of oxygen) are used to break
down the complex organic molecules. The by-products produced by
these bacteria are mostly gases such as methane, hydrogen sulphide
and carbon dioxide. These gases are vented off through the normal
ventilation system of a building’s sewage pipe system. Using anaerobic
digestion, around 40% of the organic substances found in sewage can
be broken down. To remove the rest of the organic substances to an
acceptable level, a further aerobic process is required.
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The Second Stage (Aerobic or Activated Sludge Section)
The second stage of the “GEM” Mini Sewage Treatment Plant is the
aerobic treatment section. Here a different type of bacteria is grown,
aerobic bacteria (bacteria that requires oxygen to break down organic
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African Environmental Development
Portion 129 of the farm
Sterkfontein 173 IQ
Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
Environmental
Development
substances found in sewage). Aerobic bacteria are much more efficient
than anaerobic bacteria in the breakdown of organic matter found in
sewage, but require excessive amounts of oxygen. For this reason, the
“GEM” Mini Sewage Treatment Plant is fitted with a small air blower,
which uses only 180W of power.
The compressed air is diffused into very small bubbles through a
stainless steel diffuser at the bottom of the aerobic section of the
“GEM” Mini Sewage Treatment Plant and apart from keeping the
bacteria in suspension, also provides oxygen for the bacteria.
The type of aerobic bacteria grown in the second stage of the “GEM”
Mini Sewage Treatment Plant tends to group together in the form of
“flocks”. The second part of the aerobic section of the “GEM” Mini
Sewage Treatment Plant is used to separate the aerobic bacterial
flocks from the purified water. The clean water then flows to the third
stage of the “GEM” Mini Sewage Treatment Plant, while the bacterial
flocks are re-circulated to the aerated section of the plant so that they
can continue to perform their water purifying work. In order to recirculate the bacterial flocks, an airlift pump is used. The airlift pump is
powered by compressed air from the same blower that provides air for
the aerobic bacteria in the second (aerobic) section of the plant.
After a while, the population of bacteria in the second section of the “GEM”
Mini Sewage Treatment Plant will become too large. Provision has
therefore been made to continuously “waste” small amounts of these
bacteria to the first (anaerobic) section of the plant. Here the anaerobic
bacteria consume the “wasted” aerobic bacteria in a similar manner as the
way they “consume” organic matter in the raw sewage entering the
system.
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The Third Section – Disinfection
By the time the treated water (effluent) leaves the second (aerobic) stage
of the plant, the organic load in the sewage that entered the “GEM” Mini
Sewage Treatment Plant has been brought down to acceptable levels.
There may, however, still be pathogenic bacteria left in the effluent water
from the second aerobic stage of the plant. For this reason a disinfectionsection is provided as the final stage of the sewage water treatment
process.
The disinfection section of the “GEM” Mini Sewage Treatment Plant
comprises of a chlorinator that uses a cartridge of chlorine tablets. The
type of chlorinator used on the “GEM” Mini Sewage Treatment Plant is
simple to use and to adjust.
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Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
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E-mail: - [email protected]
http://www.aed.co.za
African
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Take care of your bugs and they’ll take care of your sewage!
As is the case with most sewage treatment plants, the “GEM” Mini Sewage
Treatment Plant is a biological plant meaning that it contains living organisms
(mostly bacteria) that break down the sewage. As are all bacteria, these
particular bacterial populations are also susceptible to disinfectants and will be
killed if enough “poison” reaches the “GEM” Mini Sewage Treatment Plant.
Most cleaning material and toilet cleaners are intended to kill bacteria, so a
word of caution! To ensure that your bacterial populations in your sewage
plant remain happy and healthy, please follow these simple guidelines:
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Do not pour disinfectants down you drain unnecessarily. A little bit of
disinfectant will be diluted and will not harm your bugs. Too much will,
however, kill them. So if you have to use a disinfectant in the toilet,
bath, wash-hand basin or kitchen sink, use it sparingly. More often than
not, a good cleaning liquid (soap) which does not contain a disinfectant
will give better results when cleaning these utilities than using a
disinfectant only.
Most types of soap such as dishwashing
liquids, laundry detergents and toilet
soaps are harmless to the bugs and can
be used safely.
When purchasing cleaning liquids, read
the label on the bottle and buy only the brands that specify that the
products are “biodegradable” or “safe for septic tanks”.
Do not hang any disinfectant dispenser in the toilet bowl that produced
disinfectant every time you flush the toilet. The same applies to
disinfectant blocks that you place in the cistern of the toilet. This is
totally unnecessary, even in areas served by a municipal sewer. You
will be poisoning your bugs continuously and they will not perform their
work properly. Incidentally, municipal sewage plants are just as
vulnerable to disinfectants as the “GEM” Mini Sewage Treatment Plant.
The only difference is the dilution factor. If you pour a bottle of
disinfectant down a municipal drain, it will be diluted from other water
sources down the sewer line long before it reaches the plant. On the
other hand, if you do the same with your “GEM” Mini Sewage
Treatment Plant, the disinfectant will reach your bugs undiluted and will
kill them.
Apart from disinfectants, you should also not introduce any other items, which
are not readily biodegradable. This includes items such as sanitary pads,
which contain plastic material. Usually tampons are manufactured entirely
from cotton and are therefore totally biodegradable and safe to use with your
“GEM” Mini Sewage Treatment Plant. Sand and gravel could also fill the
anaerobic tank prematurely. When washing hands, dirty overalls, etc. that
contain excessive amounts of sand, first rinse them and dispose of this water
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Portion 129 of the farm
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Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
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E-mail: - [email protected]
http://www.aed.co.za
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outside of the homestead’s sewer. Also keep track of the amount of fat and
grease being disposed of in your kitchen sink. The bugs can degrade most
fats and greases, but the process is much slower than the degradation of
other solids. Excess fats in the sewer will become evident in the primary
section of the anaerobic tank during your routine inspections. Excess fats will
also cause sewer blockages as the liquid fat washed down the kitchen sink
will cool down and congeal further down the sewer pipe and create a
progressive narrowing of the pipe.
Environmental Management and Safety Considerations
Although the “GEM” Mini Sewage Treatment Plant is intended to replace the
septic tank / French drain entirely in all areas not serviced by a municipal
sewer, it was primarily designed to be used in environmentally sensitive areas
or in areas where the geology is such that septic tanks / French drains are not
permitted, i.e. where groundwater contamination or sinkhole formation may
result from French drains. An anaerobic septic tank does not purify sewage
water to nearly the same quality as an aerobic process.
The following items are therefore listed as an environmental/safety guide
when installing or operating the “GEM” Mini Sewage Treatment Plant.
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Safety Considerations
o Never drink the treated effluent. It has not been treated to a
drinking water standard. Mark all taps with effluent water with a
clear “non-drinking water” sign.
o Always treat raw sewage water with respect. It may contain
pathogenic bacteria (bacteria that could transmit diseases to
people coming into contact with the water). Always wear
protective clothing and gloves and wash your hands with
disinfectant soap immediately after handling any untreated
sewage or sanitary fittings.
o Although chlorine is one of the most efficient disinfectants used
in the water treatment industry, do not assume that the effluent
is safe. The chlorinator may not be adjusted correctly. Always
treat effluent as if it may contain pathogenic bacteria.
o When irrigating the effluent, never allow it to be sprayed directly
onto people or animals.
o Do not irrigate treated effluent onto vegetables or fruit that are
normally eaten raw.
o When irrigated onto the lawns of sports fields, always allow for
at least two days of drying in the sun before any sports activities
are allowed on the field, especially in the case of contact sports
where people may fall and come into direct contact with the
lawn.
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African Environmental Development
Portion 129 of the farm
Sterkfontein 173 IQ
Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
Environmental
Development
o Adhere to open dam safety principles, especially when there are
children around that cannot swim. Always protect all open dams
with some type of barrier similar to that used around swimming
pools.
o When there are children around, ensure that concrete ballast is
cast in the lids of the two manholes to prevent them from
opening the manholes. If a person falls into one of the units
drowning could result.

Environmental Considerations
o Never allow effluent to be discharged directly onto ground near a
drinking water borehole. This is of particular importance if the
underlying geology is dolomite. As a rule of thumb, provide for a
distance of at least 100m from any borehole. In dolomite,
however, there may be preferential access routes directly into
the groundwater from much further distances. Also keep the
distance from your neighbours’ boreholes in mind!
o If effluent water is discharged into an artificial wetland, always
ensure that the wetland is constructed on impermeable soil or
alternatively, construct such a wetland using an impermeable
lining. Alternatively, the use of a clay product, “Bentonite”, is a
cost-effective way in sealing even the most permeable soil
types.
o Never allow any water to stand in a permanent un-lined pond in
areas underlain with dolomite. This practice may lead to the
formation of sinkholes and could also contaminate the
groundwater.
o Ensure that there are no leaking pipes/couplings, especially
pipes containing raw sewage en route to the sewage treatment
plant. This may lead to groundwater contamination.
o Do not discharge the effluent produced by any sewage
treatment plant directly into any public stream without a water
license from the Department of Water Affairs and Forestry.
What to do with the effluent?
Although the effluent is not purified to a drinking water standard, it is
nevertheless safe and may be used in a variety of applications. There are
many ways the final effluent produced by the “GEM” Mini Sewage
Treatment Plant can be utilised.
The most useful application of the effluent is to irrigate it onto lawns, gardens
or crops. In this case, effluent will have to be stored in some form of reservoir
until sufficient effluent has accumulated for irrigation. Please adhere to the
safety principles discussed above.
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Created on 22/09/2004 08:36:00
African Environmental Development
Portion 129 of the farm
Sterkfontein 173 IQ
Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
Environmental
Development
In general, a plastic lined reservoir is the simplest
method of storing effluent water produced by the
“GEM” Mini Sewage Treatment Plant. It can also
be turned into an attractive water feature by
installing a water fountain in the reservoir. Apart
from being an attractive water feature, the water
fountain will ensure
additional oxygenation
in the holding reservoir,
which, in turn, will ensure further stabilisation of the
water. When sufficient water has been accumulated
in the reservoir, a centrifugal pump may be
employed to irrigate the effluent onto gardens, etc.
Alternatively, if enough of a slope is present, the
water could be gravitated onto the crops intended for irrigation.
A simpler alternative to the above is to use an empty standard shell of the
tanks of the “GEM” Mini Sewage Treatment Plant as a reservoir. In this case,
1200 litres of effluent water can be stored. This tank will then be fitted with a
submersible pump, operated by a float switch that will start and stop the pump
automatically when the tank reaches its full or empty levels respectively. This
is the simplest way to install the “GEM” Mini Sewage Treatment Plant and all
that will be visible above ground will be an additional manhole lid.
A third alternative to storage is to direct the effluent into an artificial wetland.
This wetland could ultimately discharge into a pond or it could be constructed
in such a manner that it would use up all the water within the wetland through
evapotranspiration. Please always keep the environmental considerations
discussed in the above section in mind, when designing and constructing such
a wetland.
Apart from these suggestions above, there are many other industrial and
domestic uses for sewage effluent not discussed in this manual.
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African Environmental Development
Portion 129 of the farm
Sterkfontein 173 IQ
Krugersdorp
Republic of South Africa
African Environmental Development
PO Box 1588
Rant-en-Dal
1751
Tel & Fax: - (+27) 11 956 6537 or 083 657 0560
E-mail: - [email protected]
http://www.aed.co.za
African
Environmental
Development
Product Specifications
From the outside, both of the units look almost identical. Internally, however,
they differ considerably. The unit specifications of the housings are as follows:
Construction
continuous injection moulding
Height:
1.4 m (base to manhole lid)
Diameter:
1.2 m
Length:
1.5 m per unit
Approximate dimensions of excavation for installation:
1.5m deep x 1.5m wide x 4.5m length
Construction
cylindrical ribbed with dome ends
Weight
40 Kg
Chambers
2 (both units)
Total capacity
1200 litres
Fluid working capacity
1000 litres
Wall thickness
5 mm
Inlet and outlet diameter
standard 110 mm, both fitted with
screw-in inspection eyes
Manhole diameter
450 mm
Manhole lid design
provision for filling with concrete
ballast
Manhole access extension
500 mm
No metallic components used in tank construction
Stainless steel aeration diffusers used in aeration tank
Manufacturer of compressor
Becker
Manufacturer of chlorinator
Klorman
Time between de-sludging
5 to 10 years, depending on the
amount of inorganic matter, such as
sand, allowed into the sewer ahead
of the plant.
As we are continually researching and improving the unit, specifications may
change without prior notice.
Contact Details
African Environmental Development
PO Box 1588
Rant-en-Dal 1751
E-mail: [email protected]
Website: http://www.aed.co.za
Phone & Fax: (011) 956 6537
Cell Phone: 083 657 0560
81903028
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