Wastewater treatment at home: three things to know
If like many houses in Ireland yours is not connected to the public sewer, you are in need of a septic tank or a wastewater treatment system.
1. Wastewater treatment at home: what are the main types of wastewater treatment solutions for domestic use?
A. Septic tanks
Generally cheaper than wastewater treatment plants, they can represent a suitable option to treat domestic wastewater. A septic tank collects the solid, more substantial material and scum contained in the effluent, and lets only the liquid flow into a suitably designed percolation area. Septic tanks don’t have any mechanical parts, reducing the need for maintenance. Septic tanks are suitable for soils where three ≤ T ≥ 50 and require a percolation area after them to improve the wastewater quality and treatment. Depending on usage, desludging (emptying) of the septic tank might be more frequent than with other wastewater treatment plants.
All septic tanks installed in Ireland should meet S.R. 66 & EN12566-1 standards.
B. Wastewater Treatment Plants
A wide variety of wastewater treatment plants are available on the market, the process of how the wastewater gets treated and the quality of effluent then released vary. However, no matter which system is in use, all the wastewater treatment plants require certification to EN12566-3. & S.R. 66 A professional Site Assessor should be contacted to assess your site and recommend the best-suited treatment units for your needs.
Types of domestic wastewater treatment plants:
– Biological Aerated Filter (BAF) or Submerged Aerated Filter (SAF)
With the BAF or SAF wastewater treatment systems, the treatment process requires three chambers: a primary settlement chamber, the aeration chamber and finally the settlement chamber. Most of the BAF systems for single dwellings are available prefabricated, with all the chambers built into one single unit. They usually commonly from GRP or concrete. The media used in these units is a fixed bed system. These are popular systems as they are easy to install, simple to use and maintain and components are easy to replace if required.
An example of a BAF system is the Tricel Novo.
– Moving Bed Biofilm Reactor (MBBR)
This system type is a similar system to the BAF or SAF (in using three chambers), the difference is that it does not use a fixed, but moving, media. The format is also popular wastewater treatment solutions, they provide good treatment efficiency and are easy to maintain.
– Activated Sludge Plant (ASP)
ASP plants use a V-shaped tank, which consists of a central aeration/biological chamber and an outer clarifier/settlement chamber, aeration is continuous. This solution generally is high in energy consumption and also generates a lot of suspended solids in the effluent, increasing the risk of clogging the percolation area.
– Sequencing Batch Reactor (SBR)
Sequencing batch reactors, or SBRs, generally treat wastewater in two separate chambers they use a primary/pre-treatment section to mechanically hold back solids and a reactor chamber to treat the wastewater. SBR wastewater treatment systems clean incoming sewage over cycles using pumps that transfer the wastewater between the two chambers. It is a popular option as it offers a high level of treatment efficiency. It is also low in energy consumption and the technology better supports the load’s variations (ideal for secondary home, extra guests).
Tricel Vitae is an SBR system.
– Rotating Biological Contactor (RBC)
RBC systems use a rotating disc to treat the wastewater, the media is submerged partially in the wastewater, and a biofilm develops on the media over time. It is this biofilm that treats the wastewater. Due to the harsh nature of effluent, and the continually submerged drive shaft, they can be expensive to repair. They are a popular solution for more substantial wastewater treatment requirements, above 700 P/E, where a dedicated person does regular service and maintenance.
– Non-electric Filters
Generally used as secondary treatment (after a septic tank) or as tertiary treatment (following a wastewater treatment plant) solutions. Non-electric filters are usually simple to install, economical, easy to maintain and provide a high-level of treatment. They all require a pump to move the effluent from the septic tank or wastewater treatment plant into them from the primary unit. The effluent then percolates through the media receiving treatment by passive biofiltration processes.
2. Running costs of wastewater treatment systems
As well as the initial cost of the wastewater treatment plant or septic tank, you should also take into account the following hidden costs:
- Ease of installation. A light, shallow dig tank is easier to install (less machinery, people, time) therefore saving you money during the installation stage.
- Energy consumption. Some wastewater treatment uses mechanical parts, air blowers, compressors and other elements which all use electricity to run. Comparing systems and making sure the running costs are low saves you money over the years.
- Guarantee and technical support. As with any appliances, check the manufacturer guarantees for both tank and mechanical parts.
- Servicing & maintenance requirements. Different systems require different servicing and maintenance. Read more in section three
3. Maintenance and repairs
As a homeowner, it is your responsibility to make sure your system is correctly installed, operated and maintained and does not pose a risk to human health or the environment.
The sludge is a build up of all solids. Both septic tanks and wastewater treatment plants require regular desludging. Refer to the installation manual and guidelines from the manufacturer regarding the frequency. It varies depending on the usage.
Only competent approved personnel should carry out desludging.
Desludging costs vary between counties and suppliers, as a rule of thumb the expense sits between €200 and €400. Make sure to get a waste disposal certificate from wastewater disposal company.
Why is maintaining your wastewater treatment system important?
Your wastewater treatment system gets used on a daily basis. Therefore, it requires regular monitoring. This monitoring ensures its efficiency, so it does not wear prematurely, and therefore lasts.
You should perform regular checks on your wastewater treatment at home, such as:
- Check the sludge level – visual inspection. If the tank is more than half full, it might be time to book a desludging service.
- Check outlet distribution box when available (the effluent should be free-flowing and clear).
- Check all vents (not blocked or covered with overgrown grass).
- Check air blower (when available); you should hear a gentle sound.
- Check for odours.
Service secondary and tertiary treatment systems on a regular basis. Some require more regular servicing than others (either quarterly, every six months or yearly). Refer to the installer’s manual for full details.
The following gets checked on a Tricel wastewater treatment plant during the yearly service:
- The functionality of blower and/or pump pressure
- Pump filters get replaced
- Pump diaphragm checked
- Alarm checked
- Ventilation function tested
- Diffuser monitored to check for dispersion of air
- Covers and locks Manifold adjusted
Making sure your wastewater treatment at home is maintained correctly is paramount for the environment and human health.
Contact our team of experts if you have any questions or would like to discuss your wastewater treatment at home.
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