Softened Water FAQs
Can a water softener be fitted with a fixed film sewage system (septic tank)? Can a water softener be fitted with a fixed film sewage system (septic tank)?
1.0 Introduction
Tony frost, Aquafocus, had expressed concerns at a British water focus group meeting that the water softener industry was getting an unfair reputation for effecting small single household sewage treatment plants. It was agreed by the focus group that Richard Munden would trial the Harvey water softener and report on the matter.
2.0 Summary.
Initially the treatment plant had a slight problem in adjusting to the change in conditions. It may be nothing to do with the salt regeneration process just the dramatic change over a few days going from very hard water to soft. The plant has performed since the initial “hic-up” with no noticeable difference to the final effluent quality.
The benefits are that the use of detergents has dropped by 30 to 50%, which can only benefit the plants performance. Soft water has been beneficial in clearing up a case of eczema in a family member and that skin care/health has improved generally.
3.0 Treatment plant
The trials was conducted on a WPL mini-Hipaf that had a treatment capacity of 300 grams of BOD per day and 1000 litres per day of dry weather flow with a peak flow of 3 times DWF. The biological process used was a random packed submerged aerated filter that had been installed in 1996 and closely monitored so that the performance of the plant was well known.
4.0 Trial
A Harvey’s Block Salt Softener was supplied. The unit was easy to install in a cupboard near the sink unit. All water, except the main kitchen sink for drinking and cooking, was put through the softener. Two salt blocks slowly dissolve for the regeneration process, which is triggered on the amount of water treated. Each block weighs approximately 4 kgs and is 90 x 60 x 270mm. They are very easy to replace. The dates of replenishment (each time two blocks added) were:
1st 8.4.04 (commissioning), 2nd 29.4.04, 3rd 20.5.04, 4th 10.6.04, 5th 1.7.04, 6th 16.7.04, 7th 18.8.04, 8th 18.9.04, 9th 15.10.04, 10th 10.11.04, 11th 6.12.04, 12th 30.12.04.
On average the salt blocks last 3.2 weeks, and the cost to run the softener is £77.00 per annum.
The amount of detergents used is much less. Although no records were kept it is estimated the savings were at least 30%. It may be that with more careful application of washing and dishwasher detergents further savings could easily be made.
Trial period 4th April until 30 December 2004.
5.0 Effect on the plant.
The plant started to perform slightly worse for about 10 days and the final effluent went very slightly cloudy. However, the plant was due for a desludge which was completed 3 weeks after the water softener was commissioned. A week after the plant was de-sludged the plant was back to normal performance. Slightly more oils fats and grease were present in the primary tank but this may be due to changes in cooking or that less surfactants were being used that may emulsify the Oils, fats and greases.
The hockey leg diffusers used to aerate the SAF were taken out and there was no effect on any scale built up, the holes in fact had no build up whatsoever. Usually there was a build up over a 9 to 12 month period, sometimes blocking a hole.
6.0 Consumers’ viewpoint.
The positive benefits of soft water on bathing and cleaning alone are sufficient that if we moved to another house with hard water my wife would insist on installing a water softened, she is converted. The space the unit takes up is a minor nuisance. The system is easy to use, salt replenishment is very user friendly and it is very straightforward to understand when to do it.
The health benefit of significantly reducing eczema in a family member has been a bonus and in another reason why we would fit a similar unit in the future.
7.0 Conclusions.
I can see no reason why a well-designed, single-house treatment plant should be adversely affected by a water softener. On sites where large amounts of detergents are used, i.e. young families, then there may be an advantage to the treatment plant from softening the water supply in hard water areas.
8.0 Future trials
It has been agreed to repeat the trial on an activated sludge treatment plant for a single house application to check that this process is not affected by the installation of a water softener unit.
Richard Munden 31st January 2005