On-site wastewater systems for holiday homes

As many embark on a summer holiday or perhaps are just returning from one, they may enjoy staying at their holiday home, a weekender, or have rented a house or apartment by the beach. Whatever you call it, if you own a property outside of main sewered areas that is used sporadically, you will have some very specific needs when it comes to a wastewater system.

Many on-site wastewater systems will perform sufficiently under constant flow conditions but are not designed for large peaks and troughs. Why is this so and what are the key performance factors that you need to consider when deciding on a wastewater treatment system for such properties?

Firstly, the type of process is important. Many treatment processes depend upon very few trophic levels of organisms for treatment, living in concentrations far higher than found anywhere in nature. The process is artificial and needs to be maintained at constant levels to ensure stability. In essence, the bugs treating the effluent need food and they need the right amount of food. Sharp decreases or sudden shock loads are not well handled.

Aerated Wastewater Treatment Systems (AWTS) require an unnatural environment to be maintained by input of energy (via blowers/aerators) which is critical to maintaining process integrity and a close attention to operating conditions is required over the short term. Conditions that upset the system, in this case flow variations, will see the system ‘off track’ and it typically takes some time for the system to return to normal. During this time, poorly treated effluent continues to be produced and sent to the land application area.

Many systems also have slow start-up times. AWTS typically require several months to grow sufficient populations of microorganisms that provide wastewater treatment. This certainly doesn’t suit a weekender or infrequently used property.

The last thing you want while you are trying to relax with the family and friends on holiday is that putrid, untreated sewage smell. For a system that is not operating well, and one in particular not designed to handle the high shock loads, that is just what you will smell. Depending on the system, you may also hear a loud noise with pumps and blowers operating constantly.

I bet you’d like to be able to do nothing special when the house is empty for a few weeks or months. With no food entering the system the bugs in an AWTS will die, which is why some AWTS manufacturers recommend pumping the system out and filling it with water prior to powering off. You will then have to weather the slow start-up on your return.

The Orenco AdvanTex treatment system, new to Australia in 2009 but with over 20,000 systems installed worldwide, is a good solution where sporadic flows are apparent. The system is a recirculating textile filter, using low-energy turbine pumps and a bed of hanging synthetic textile sheets to treat the wastewater. Microorganisms living in the textile media digest the organic matter to provide consistent high-quality effluent. The AdvanTex uses completely natural processes, which are stable and robust, to treat the wastewater during periods of high activity or when no-one is home.

Key features as to why the Orenco AdvanTex treatment system is suitable for these applications include:

• Quick start-up after periods of non use - 80% removal of BOD is typical within 24 hours of start-up, with TSS less than 15 mg/L within this period.
• Reliability under peak flow conditions - under 10 mg/L TSS and BOD most of the time but never more than 30 mg/L under peak loading.
• Large (4000 L) primary tank offering 24-72 h reserve if there is an outage and ensuring no flood dosing of system.
• Small footprint and lightweight - suitable for small and difficult sites
• Chemical free - uses UV light for disinfection for sensitive sites
• Natural/passive process - does not depend on inputs in energy or adjustments in operating conditions once set. Naturally occurring micro-organisms populate the textile fibres at population levels similar to those found in nature
• Sludge removal - not required from textile filter itself as most of sludge retained in primary tank (pump outs every 8-12 years)
• Low operation and maintenance requirement
• Fail safe - the AdvanTex design does not allow for untreated sewage to be released, since wastewater must pass through the treatment media before discharge
• Managed flow - since the Advantex has a programmable timer in its control panel, there is the ability to detect inflow caused by higher than normal water consumption.
• Automatic holiday mode - when flows are low a signal is sent to the control panel which triggers 100% recirculation and less frequent pumping, saving power.