Septic Systems, if you live on a rural (or a semi rural with no mains sewage access) are a necessarily evil. What 'deposits' your family and friends produce need to be processed in a safe and effective manner by a Septic system that is able to cope with the peaks and troughs of waste production over an extended time frame, and do all of this reliably without breaking the bank in the meantime.
At first glance, it looks like an easy job to do, but there are particular problems in on site waste processing that can occur which can rather ruin your day if not dealt with properly. We will go into these main 'variables' now.
Different Types of Waste
Waste carried in water is usually broken down into two categories: black and grey water. Black water contains human sourced wasted (poos and pees) and comes with what was flushed with such deposits (like tissue paper). Gray water
, on the other hand, is lightly soiled mains water, think of shower water, sinks, washing machine, dish washer water, etc - it contains no directly human sourced waste as such.
Now, apart from the actual content in the water, what also tends to distinguish black from grey water is volume of water involved. Black water has a much higher 'solids' loading than grey water.
Why does this distinguishing matter? Well, you can set things up so that the grey water is 'diverted' to a dedicated grey water system
, which once treated or filtered, can be put straight into the garden (although typically not onto your veggies). Where as Black water requires a much more processing before it can be distributed in the garden (usually by sub surface weep pipes on a 'drain field'). Although this distinguishing can be a muddied by the fact certain Black Water treatments require a high volume of water to work effectively (i.e. you put in the Grey with the Black)...
Septic System Treatment Types
Septic Systems in a residential context can usually be grouped into the following types:
- Anaerobic Settling Tanks
- Aerobic Treatment System (ATS) or Aerated Wastewater Treatment System (ATWS)
Anaerobic Settling Tanks
These are typically what most people think of when they refer to a Septic System. This operates by having a large tank (often below ground) which is split into two sub tanks. The first tank takes the raw waste and acts as a settling tank, so that the solid matter which cannot be broken down sinks to the bottom of this tank as sludge. An opening between the this tank and second, typically below the inlet height and the maintained water level, allows the cleaner water to migrate into the second tank. In the second tank the smaller solids that cannot be processed again sink to the bottom as a finder grade sludge. The final secondary effluent leaves by an outlet which is set just at the height of the water via a submerged pipe - the idea being its drawing out the water below the surface.
This movement of the water between the tanks and the final drawing out below the water height is important, as a 'film' of floating and breaking down waste will occur on the top of the water and you do not want this going into the outlet. This film is doing the first 'active' biological breaking down of matter, which then sinks below into the anaerobic waters below, where only anaerobic bacteria can work on the waste and do the final breaking down of the waste.
Such systems can often be set up to be gravity feed with the final treated effluent flowing into a septic drain field, where microbes in the soil further process the secondary effluent.
Periodically, the sludge will need to be sucked out of the tanks to avoid them filling up, but apart from that there is not much to be done.
Anaerobic Settling Tanks - Advantages
- Cheap to operate - depending on the size of tank and its loading - you might only need to empty the tank once or twice a year. There are many operators who perform this service.
Anaerobic Settling Tanks - Disadvantages
- Can become blocked if not careful - Oils and Fats can accumulate and block the pipes.
- Excessive water will cause a flush - too much water coming into the system will result in the tanks 'flooding' and poorly treated water making its way into the drain field.
- Roots from trees invading the drain field - left unchecked your drain field can block and the effluent either backs up or breaks out to the surface (causing a smell 'bog').
- Odors and gases - such anaerobic systems can smell and both produce gases which make the tank a 'dead space' (i.e. if you go into it you will be quickly overcome by the fumes and die!).
Aerobic Treatment System (ATS)
An aerobic treatment system is similar to a septic tank
system, but it uses an aerobic process for digestion rather than just the anaerobic process. Unlike the traditional anaerobic septic system, the aerobic treatment system produces a high quality secondary effluent, which can be sterilized and used for surface irrigation. This allows much greater flexibility in the placement of the leach field. Such systems are often seen as been more 'Green', but this often a question of perspective.
The ATS process generally consists of the following phases:
- Pre-treatment stage - Removes large solids and other undesirable substances.
- Aeration stage - Where aerobic bacteria digest biological wastes.
- Settling stage - Allows undigested solids to settle. This forms a sludge that must be periodically removed from the system.
- Disinfecting stage - Chlorine or a similar disinfectant is mixed with the water, to produce an antiseptic output.
Some of these stages can often be combined into one stage, it all depends on the design of system employed and the loading of primary effluent that needs to be reliably processed.
Aerobic Treatment System - Advantages
- Effluent Quality - the bioload in the final effluent produced is so low it can be safely discharged into the environment without it resulting in the creation of a 'slime pit' or smell. This is particularly important if operating in an environment with native plants which are sensitive to excessive nutrients.
- No Bad Smell - The smell produced is typically characterized as a musty smell and not associated with sewage at all. So can be used in semi rural situations where you have a high population density, or in situations where a sewage smell would be most off putting (say a rural restaurant).
Aerobic Treatment System - Disdvantages
- Higher cost to install than anaerobic - Due to the more complex design and the requirement for electricity (to force air to interact in the treatment process) you will spend typically twice as much for this as a basic Anaerobic system (although you might not have much choice, see later).
- Higher Cost to Operate - The system will need to be checked either annually or quarterly to ensure the effluent produced is within the acceptably quality range and to make sure everything is working as it should. Also you will need to periodically clear out and rebuild the system due to the build up of solids.
- More sensitive to loading - having a party at your house could result in your Aerobic system getting overloaded and flooded - typically once that happens it will need to be serviced. You need to be very aware of the permitted maximum daily loading.
Septic System Regulatory Environment
Given these system process human waste and dispose of the final treated effluent within the local environment, a whole raft of regulations and legislation has developed (and is being developed, more later) to ensure quality and to protect the environment. The legislation typically relates to the following:
- Quality of the final effluent - The regulations will typically set maximum levels on suspended matter (turbidity) and nutrient loading.
- System Monitoring - If a system fails, a maintenance person must be notified.
- Certification of System - Approval to install and maintain a system as described.
- Installation Approvals - Assessment and sign off of install meets standards.
- Certification and Licensing of Installers and Servicing personal - ensure those who install or service the systems know what they are doing and are current in their knowledge.
- Inspection & Servicing Routine and Operational Approvals - Periodic inspections and approvals given to operate until next inspection with Servicing reporting and ascertainment of fit for purpose.
Such legislation, regulation and standards can derive from many bodies and often interrelate, sources being:
- National or International Standards Bodies - either Country (USA, Australia) or regional (Europe) or global.
- National or Regional Government Legislation - think USA, Europe, etc - this often enforce the standards defined above.
- State Government Legislation - think NSW or California...
- Local Government Legislation - yep, local governments get in on the act and have their own requirements.
The net effect of all this that what is acceptable can drastically change if you move between one Council or State and another - also what can be installed where can and does vary over time... Basically do not try to sort out this mess on your own if you are looking to install a Septic system, get the opinions of several professionals (ideally at least 3) before you do anything; as their knowledge is unlikely to be complete as well. Also some of the regulations can be applied retrospectively, so what was okay in the past will need to be replaced!
It is also highly likely that some of this regulatory 'mess' has been driven by the Septic business themselves, as regulation can often be used to create barriers of entry to a market to protect the incumbents from new competition. Far easier to get the governments to put your competition out of business by changing the market conditions against them. It can also be used to create 'new' markets by making existing installations redundant. To give you an idea of how complex this whole area can be just visit this page
that lists most of the parties involved in setting regulations and standards in just Australia.
New Septic Systems Standards 2020
United Kingdom Septic Standards
- By 1st January 2020, septic tanks will now longer be allowed to discharge directly to a surface water such as a river or a stream. You will probably have to replace the old septic system with a treatment system. The new system will need to be correctly specified with the right capacity for the levels of usage and must meet the BS EN 12566 standard. Once installed, the new treatment system must be regularly emptied and maintained.
- Septic tanks that currently discharge via a drainage field into the ground are not expected to be affected.
Septic System Do's and Don'ts
- DO keep a record of inspections, servicing, etc - thereby making it easy to see how the system is performing over time.
- DO read the documentation that comes with the system and make a note of how often the system needs to be serviced and when it needs to be drained or rebuilt.
- DO use cleaning products that are specifically septic safe.
- DO NOT put large amounts of water into the system unless it is specifically designed to deal with the in rush.
- DO NOT put oils or fats down the sink.
- DO NOT put food scraps down the drain.
- DO NOT flush nappies, tampons, condoms and other man made items that do not biodegrade down the toilet as they can cause blockages.
- DO NOT drive or park motor vehicles on the drain field.
- DO NOT allow livestock on the drain field.
- DO NOT plant trees close to the drain field.
- DO divert surface water away from the drain field.
- DO use a lint filter on your laundry outlet.
Keeping your Septic drain field healthy
First off you need to make sure that your septic system is in good working order and that it is producing effluent which the drain field can process. Effluent with too high a turbidity
or nutrient count will attract roots to the piping and block it.
If you are finding it difficult to keep your field 'clean' - there are a few things you can do:
- Filter out the solids making their way to the field, a simple inline disc filter (40 microns), will stop this. Get one which you can take apart and clean easily.
- Add root poison via an inline feeder, this prevents root intrusion. Note: do put in a ball valve before this feeder so you can stop the treated effluent going back to the tank if it is serviced and the pipe is disconnected at the pump end (which often results in the charge in the pipe going back into the tank..)
- The old dose of chlorine to pool sanitation levels will help inhibit root growth and break down matter in the pipes (basically a bucket of pool water after a recent 'shock' down the line).
Biological Eco Friendly Septic Systems
Finally, a word about Eco Friendly
Septic Systems. These are usually characterized as follows:
- Worms and specific bio mass form part of the operational matrix of the system to break down the solids quickly.
- They are either one big tank installed in ground, or a series of tanks or beds that process the waste.
- They depend upon a multiple stage filtering system using a series of biological and mechanical filtering processes.
- Often they require electrical power to run pumps and air blowers.
To be honest, usually the only 'Eco Thing' about such systems is its use of the Worms or specific bio mass; the rest is just standard Septic techniques of one of the two major forms detailed above. You cannot really get away from this, as the standards are very specific on what is permitted to go into the drain fields - so at some point there needs to be either true filters or UV treatment to get the effluent to the required standard. If you look at it this way, all the bio processes that go in the drain field is very Eco, so all Septic Systems, if running right, can be considered Eco Friendly...
Also, like all other Septic Systems out there, the solids will accumulate over time, all the grit and other parts which do not break down have to go somewhere and the bottom of the tanks is where it will all end up given time!
So, although it may seem strange for an Eco focused site to be saying this, more traditional Septic Systems can be just as Eco if they are run correctly, and probably with less worry to yourself, as you will not be running something 'peculiar' that depends upon the whims of one supplier or service agent.