Most rural properties and many small townships in NZ rely on onsite treatment for their wastewater where no council connection is available. Approximately 18% of NZ’s population relies on this method. Onsite treatment, or septic tanks as they are more commonly known, come in many different forms with a varying level of technology. Over time, both technology and regulations have evolved so a brand-new system could be very different to what you may have had growing up.
A general guide to septic systems in NZ
Most people don’t give much thought to wastewater and leave it to the last minute, or give it no thought at all and only realise it is needed when council return the building consent. We understand it’s not the most exciting topic but it is essential to being able to live comfortably on your property
All new and replacement septic systems must comply with AS/NZS1547:2012 and be approved by local and/or regional councils before being installed. Different councils have differing rules and expectations for these systems so it important to work with a professional who understands the local rules and requirements.
The soil and site characteristics of your property play a large part in the type of system that can be installed. Poorly draining clay soils require a higher level of treatment and a larger outfield area, this is to avoid over-saturating the ground. A well-drained site can offer more options but any system must still comply with local regulations.
Expectation vs reality: We’ve lost count of how many times we are asked for something that takes up no space, uses no power, doesn’t require servicing, is cheap and can be delivered yesterday. To avoid falling into this trap, do your homework early on and engage a designer so you can work your wastewater system in with the rest of your property layout. It doesn’t always have to be a burden, a well-designed system can have benefits like free irrigation to planted areas.
How do septic systems work?
Systems can be thought of in two halves, the treatment tank and the drainage area (also commonly known as a field drain, driplines, sand trench, outfield among other terms). Most of the treatment happens in the tank but there is also some treatment that occurs in the ground afterwards.
Wastewater from the house drains should fall by gravity into the treatment tank so the tank is usually located near the dwelling, but most modern systems feature a pump so the discharge field can be placed further away. The pump also allows for even distribution over the entire field resulting in an increased field service life.
Generally speaking, most systems fall into either primary or secondary treatment categories. Primary systems like our B52 utilise the age old settling principle of allowing solids to fall to the bottom and fats and oils to float to the top leaving a clear section in the middle which is then taken for dispersal to land. Modern systems commonly include filters and pumps to increase performance. These systems require well drained soil and an engineered disposal area. It is worth noting that this level of treatment is not always considered enough for some regions and councils.
Secondary treatment such as our ABS2000 begins in the same way as primary but then adds an aerobic stage where air is introduced into the system. This allows the formation of aerobic bacteria which treats the wastewater to a much higher standard. Most secondary systems also include some recirculation within the tank which reduces total nitrogen, further reducing the impact on the receiving environment.
The importance of septic systems for rural homes
Aside from the obvious need to dispose wastewater, councils will want to see a detailed plan for wastewater before granting consent to build. Engaging a wastewater professional early in your project will save a lot of stress and surprises later on. A properly designed, installed and maintained wastewater system will reduce the risk of illness, contamination, ponding and last but not least: the risk of compliance action!
Environmental benefits of proper septic system management
The importance of ongoing maintenance and servicing cannot be understated. There are of course the regulatory requirements to do so but there are many benefits to gain from these services. Think of it like getting your car serviced, it will increase service life, detect any issues and keep things running as the should be.
Rural properties do not pay a wastewater rate to their council when this service is not provided, this saving can be put to good use by engaging a service contractor. A well maintained system reduces the risk of overflow, premature component failure, poorly treated effluent and the associated risks to groundwater, waterways and human health. Well designed and maintained systems may also be beneficial to the environment by providing irrigation and nutrients to planted areas.
Onsite wastewater treatment can be a daunting process, feel free to reach out to us for help and advice on your new project. As a company that designs, manufactures, manages installation and provides a commissioning, servicing and callout service we are well placed to answer your questions.
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