FAQ's
Below are some questions that we often get
asked.
If you have any other queries that you need answering then please
contact us
What is "Consent to
Discharge"?
Why do I have to have "Consent
to Discharge"?
How long does it take to
get "Consent to Discharge"?
Do I always need a "Consent
to Discharge"?
What is the difference between a septic tank, cess
pit and a Package sewage treatment plant?
How does a Biodigester work?
How long does it take to work?
I have a pond on my land, can I discharge the treated
effluent into it?
Do you install the Biodigester
What is BOD 5?
Can I use normal household cleaning chemicals?
Can I use a sink garbage grinder?
What is population equivalent?
What is "Consent
to Discharge"?
It is a legal document that is issued by:
Each authority may lay down specific measurable parameters which
you will have to satisfy to enable you to discharge the treated sewage
effluent from your premises into a watercourse, soakaway or sub irrigation
system.
In some areas ‘Consent to Discharge’ is not required.
Why do I have to have "Consent to Discharge"?
In England and Wales ‘Consent to Discharge’ is a legal
requirement under the Water Resources Act 1991. (Schedule 10) (As
amended by the Environment Act 1995). However legislation and interpretation
of the legislation alters from area to area. In some areas ‘Consent
to Discharge’ is not required. Always consult the appropriate
regulatory authority.
How long does it take to get "Consent to
Discharge"?
The maximum period normally allowed is 4 months. We can undertake
the application if you buy a BIODIGESTER.
Do I always need a "Consent to Discharge"?
Not always. It is wise to check with the Environment Agency or other
regulatory authority. In some areas ‘Consent to Discharge’
is not required for new projects. In most areas ‘Consent to
Discharge’ is not required if you are replacing an existing
system. CHECK
What is the difference between a septic tank,
cess pit and a Package sewage treatment plant?
There is often a serious lack of understanding of the different systems
available. There are significant differences in the range of applications
and a wide variety of types, makes and arrangements of most of them.
The following should help to clarify the situation.
There are three common types of holding or treatment system in use
which can be supplied by a number of companies in various forms. Alternatively
systems may have been constructed on site using local materials.
Cesspits or Cesspools
Do not provide any treatment at all, they are simply a holding tank
which must be emptied by tanker on a regular basis. They are large
structures, unsuitable for domestic use due to operating costs and
they are the least favoured option under present regulations. You
may come across the term cesspit used to describe what is actually
a septic tank – See below.
Septic tanks
Provide minimum treatment and must now discharge to a soakaway only.
These are generally only used for smaller domestic developments and
are nowadays less acceptable to the planners.
Biological treatment plants ie Biodigesters
Provide a much higher level of treatment than septic tanks and may
discharge to a water course, provided a Consent to Discharge is in
place. Modern packaged plants are the officially preferred option
at present.
Septic Tanks and Sewage Treatment Plants
Soakaways
..or sub-irrigation systems for dispersal into the ground. These
are constructed in different ways according to location but the
preferred method is now a system of interlinked trenches. Design
of a new soakaway is subject to the results of porosity or percolation
tests.
Package Sewage Treatment Plants.
Discharges to a water course may be direct or in-direct. Indirect
refers to a soakaway ortertiary reed bed with an overflow to a watercourse.
Systems such as this are now commonly used and are referred to as
‘Partial’ or ‘Seasonal’.
Reed beds, constructed wetlands and mounds.
These are often used where the ground conditions and water table
are unsuitable for traditional methods of effluent dispersal. They
can take up large areas of ground and may be expensive to build.
Other Systems.
A number of other systems have been used recently with varying degrees
of success.
How does a Biodigester
work?
Air is blown into the BIODIGESTER by an electrically powered compressor
mounted normally within 10 metres of the sewage treatment plant. The
air is diffused from the bottom of the central chamber. This increased
oxygen supply accelerates the activity of the naturally occurring
micro-organisms which degrade the sewage to a clear effluent and a
non toxic sludge. The plastic media is used to provide a high surface
area for the micro-organisms to adhere to and also, as it is mobile,
to facilitate rapid degradation of solid matter. The diffused air
also operates as an ‘Air Lift’ which recirculates solids
from the outer ‘Settlement Chamber’ to the inner ‘Treatment
Chamber’. This recirculation also ensures that both chambers
remain aerobic. The process runs continuously 24 hours a day. The
plant is designed to confirm to the requirements of BS6297:1983.
How long does it take to work?
About six weeks from start up. You can accelerate this by seeding
the unit with the sludge from an operational aerobic sewage treatment
system.
I have a pond on my land, can I discharge the
treated effluent into it?
The answer is dependent on the size of the pond, size of the discharge
and whether there is a flow through the pond. ‘Consent to Discharge’
may be required. Please consult BES.
Do you install the Biodigester?
In some areas we have independent contractors who specialise in installing
sewage disposal systems. More contractors are required. Please ask
for details.
What is BOD5?
BOD stands for Biochemical Oxygen Demand. ‘5’
stands for a test that takes 5 days to carry out.The test is essentially
a measure of the ‘Organic’ or ‘Polluting’
strength of an effluent. A measured sample is prepared for incubation
and the oxygen level is determined.The sample is than incubated for
5 days at 20°C and the oxygen level is measured again. The difference
in oxygen levels is used to calculate the BOD5. This represents the
level of activity by micro-organisms naturally present in the effluent.
The level of activity is proportional to the ‘Organic’
or ‘Polluting’ strength.If an effluent is too strong for
a receiving aquatic environment then oxygen will be naturally depleted
in the same process. Mg/l stands for Milligrams per litre. One Mg/l
is the same as one part per million. Untreated sewage typically has
a BOD5 of 400-500 mg/l. The Biodigester reduces this to less than
20mg/l.
Can I use normal
household cleaning chemicals?
All normal products can be used in sensible quantities. Don’t
forget that the system works by accelerating the natural sewage degradation
process. Some chemicals used are designed to destroy micro-organisms.
So, overuse of bleach or antibacterial cleaners may upset the process.
You should avoid products containing ammonia where the ‘Consent
to Discharge’ has a limit for Ammoniacal Nitrogen. Avoid allowing
significant quantities of grease to enter the system. Where there
is a commercial kitchen (Hotels, Pubs etc) a grease trap must be fitted
to the kitchen drainage only.
Can I use a sink
garbage grinder?
Yes but it will decrease the capacity by 35% and increase the emptying
frequency. It would be better to compost this waste.
What is population
equivalent?
Population Equivalent relates to non domestic sewage treatment plant
applications. For example an office with 30 workers is equivalent
to 10 domestic residents. ie the PE is 10. This becomes more complicated
for Pubs/Hotels etc. Please refer to the programme on this site for
specific details. Pubs typically have a PE in the range 40-200.
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