Septic system options

If you are a considering building a new home or if you are a home owner with a failed septic system that needs replacing, you will have to ask yourself the question: “What type of septic system should I invest in?” This is a major decision and there are a few basic options to consider. Your first line of approach is to discuss with your contractor if your location is subject to Government restrictions on using regular septic tanks with drain fields or soak-aways. The St. Kitts Planning Board has designated specific areas which require full-blown wastewater treatment and in those areas you will have no option but to invest in a wastewater treatment plant. Half Moon Bay, the South East Peninsula and areas in Frigate Bay are subject to this restriction. The reason homeowners have to install wastewater treatment plants in these areas is the lack soil depth. If you are building on rocky substrate or shallow soil that absorbs poorly, wastewater will not be treated sufficiently which can contaminate ground water. Therefore wastewater in these areas must be fully treated in a contained system before it is dispersed into the ground or a drain. If you are building in an area where no such restrictions apply you essentially have three options available to you: 1. A basic septic tank 2. An aerated septic tank 3. A wastewater treatment plant

The workhorses of any system

Before outlining how the various options for wastewater management work, there are two key players present in all tanks. However, the real workhorses of any septic system are not even visible to the eye...bacteria and oxygen! The reason we have different tank systems available is purely down to how we make those two interact. So just a quick word on aerobic and anaerobic bacteria is in order. The terms aerobic and anaerobic refer to the presence and absence of oxygen respectively. Bacteria that are found in regular septic tanks where a limited amount of oxygen is available for them to breathe and multiply are called anaerobic bacteria. They scavenge oxygen from the small amount dissolved in the influent water that comes from your house into the tank, but also from the food waste contained in that water. They tend to produce methane and hydrogen sulphide gases, both of which are associated with ‘that septic smell’. Anaerobic bacteria are useful for breaking down phosphates and nitrates. Aerobic bacteria are found in modern wastewater treatment plants where oxygen is artificially introduced through aeration. The oxygen dissolved in the water allows the bacteria to breathe and reproduce rapidly. These bacteria are much more aggressive than anaerobic bactera and, by using free oxygen from aeration, are capable of breaking down solids to a higher level and up to 5 times faster.  

Basic septic tanks

Regular septic tanks offer the most basic form of septic wastewater treatment. They contain anaerobic bacteria as described above. Consisting of one tank with two internal compartments and no equipment, the tank collects wastewater from your home and treats it through a natural process whereby anaerobic bacteria break down the solids in the water. This process happens in the first compartment. Solids will fall to the bottom of the compartment and settle (referred to as ‘sludge’) while scum and grease will float to the top. Above the scum a layer of septic gas forms that is generated by the chemical process that occurs inside the tank. This gas is vented out to avoid pressure building up in the tank. The layer of liquid in between the sludge and scum will flow through a sanitation Tee fitting in the baffle to the second compartment where it continues the same process as in the first compartment. Incoming water to the septic system then pushes the clarified water towards the outlet pipe which leads to a drain field where it will be dispersed into soil. This is where the actual filtration of the water occurs as sandy layers in soil will naturally filter the effluent.

Aerated septic tanks

Some septic tanks are fitted with an aerator that introduces oxygen into the first compartment of the septic tank. This process allows aerobic bacteria to thrive. As mentioned above, the introduction of oxygen stimulates the aerobic bacteria to break down waste up to 5 times faster than a regular septic system, and to a much more effective level of solids breakdown. The treated water flows into the second compartment, where anaerobic bacteria continue the task and any remaining solids settle to clarify the water. The clarified water from an aerated septic system is cleaner than that from a regular septic system and is therefore less likely to cause failure of the drainfield over time.

Wastewater treatment plants

Wastewater treatment plants work on the same biology principle as septic tanks. There are, however, some major differences. Rather than having two compartments, our wastewater treatment plants have three compartments. The first compartment separates liquids from solids the same way a septic tank would, but this process is merely considered pre-treatment. The second compartment is where the main treatment happens. It receives the partially treated water from the pre-treatment compartment and starts a more intense process of solids breakdown by not only introducing oxygen via an aerator, but also by the presence of Jet’s patented BAT media. BAT media consists of layers of purposely designed plastic sheets that provide an ideal environment for aerobic bacteria to grow more actively and therefore process waste more efficiently. The main difference compared to a septic tank is the third compartment where wastewaterwater is clarified and then passes through a filter before the process of sterilisation. Most wastewater treatment plants traditionally use chlorinators to achieve sterilisation. Chlorine is known for it’s qualities to sterilise, but it has downsides too. Chlorinated water, although clean, is not the best thing for the environment. At Fibre-Zone we therefore prefer Jet Inc.’s system that uses UV light to sterilise wastewater. The UV light sterilises wastewater to well below the most stringent U.S. treatment standards without forming by-products that can harm the environment once the effluent water leaves the plant. Because the effluent water sterilised, it is suitable for re-use. Although not of potable quality, it is clean enough to safely use it for irrigation purposes, discharge into to ponds or waterways, flushing toilets etc.. This is why many homeowners choose to add a second tank to their plant which collects the sterilised water for re-use. The investment in a collection tank makes sense in warm climates that have long dry spells. Irrigating your garden can easily constitute a big cost factor in your water consumption, as can toilet flushing. Re-using your wastewater is a major budget saver that repays for the additional tank in just a couple of years.