- This topic has 7 replies, 5 voices, and was last updated 20 years ago by Guest.
15 Apr 2001 at 12:25 am #278958MasterPlumbersKeymaster
The health department has limlited my building site to one of the following alternantive systems: Recirculating or intermittent sand filter; extended treatment system. I have plenty of land but rocky soil. Are these systems reliable and which one would you recommend? Any idea on cost? Thanks
15 Apr 2001 at 4:16 pm #299684John Aldrich1
Gayla Mae, the recirculating sand filter has the ability to remove a significant amount of nitrates from the sewage effluent through the process of denitrification. The effluent of the sand filter must be reintroduced into an “anaerobic” environment, normally back into the septic tank, in order for denitrification to occur.
The intermittant sand filter actually increases the level of nitrate in the effluent through the process of nitrification of the ammonia. If the level of nitrate in the final effluent is not a limiting issue, then the intermittant sand filter is the option to choose. Both systems are very reliable if, as is true with all sewage treatment systems, they receive regular maintenance. Each type of system has the ability to remove from the effluent significant amounts of BOD, Suspended solids, bacteria, and viruses.
These systems are relatively expensive when compared to a standard septic tank/soil absorption system. A recirculating sand filter recently installed in the mountains of Colorado, cost approximately $20,000, which includes the cost of excavation, and installation on a steep, rocky slope. The cost of a septic tank/soil absorption system to serve the home if adequate soil was present would be about $5,000.
Orenco Systems Inc. markets a package system for either of the alternatives that you mentioned. They also sell other alternative systems.
A more passive approach to creating an extended treatment system is to utilize a subsurface flow constructed wetland filter, and a soil absorption system for final disposal of the highly treated effluent. The wetland filter provides excellent treatment of septic tank effluent, and also provides for a wetland landscaping amenity, additional wildlife habitat, and a few thousand gallons of water which can be used for wildfire suppression.
If adequate slope is present on the site, this alternative system does not require an effluent pump. A constructed wetland filter system for the above mentioned home would cost about $16,000. If you would like more information regarding the constructed wetland filter technology, send me an e-mail message at email@example.com
A website that reveals many facts about septic systems in general can be found at the following address.
Good luck on your quest for the most appropriate system to suit your needs.
Septic System Consultant
[Edited by John Aldrich on 15 April 2001]
15 Apr 2001 at 7:43 pm #299685Guest
First of all, thank you very much John for your comprehensive reply. It’s quite admirable that you share your knowlegde and experience with us less knowing.
You mentioned that nitrate could be an issue. Would you explain further?
15 Apr 2001 at 11:46 pm #299686John Aldrich1
Gayla Mae, in areas where the groundwater is used as the drinking water source, nitrates from septic tank effluent could become a contaminant if the concentration of septic systems is too great. The USEPA maximum contaminant level (mcl)for nitrates in drinking water is 10 parts per million (ppm), or 10 milligrams per liter (mg/l). This very low mcl for nitrates is ridiculous in my view, considering that high nitrate concentrations in drinking water affects a miniscule percentage of the general population, but that is another issue. I am unaware of the mcl for nitrates in drinking water in other countries of the world.
The traditional approach employed to control high nitrates from septic tank systems in groundwater is through dilution. Minimum densities of septic systems to attain the proper dilution of nitrates are generally half acre densities, but this area could be greater depending upon the natural background levels of nitrate in the groundwater. The sewage disposal system regulations in some jurisdictions in the USA require nitrate removal capabilities of a treatment system to produce an effluent with no more than 10 mg/l.
If the health department regulations require nitrate removal from the septic tank effluent, then the recirculating sand filter will accomplish this. If the discharge of nitrates to the groundwater is not an issue on your specific site, then perhaps another technology would be more appropriate.
It is difficult to advise you as to which technology to choose without knowledge of the regulatory constraints, and site constraints that must be considered. It is particularly difficult to make a more specific recommendation to you because you have chosen not to reveal your geographic location in the world.
Septic System Consultant
16 Apr 2001 at 12:34 am #299687Guest
I was interested in your reply.
Here in the Cook Islands we are going through the problems of supposedly nitrates etc leeching through to our lagoons.
The main problem we have is outdated standards and lack of of enforcement.
I have seached around a bit on the net on the septic subject but have not come up anywhere with let us say the “latest” standard.
Eg single, double, 3 chamber are the recommended standards. Standard to have effluent filters on the outlet.
Sizing and plans?
The “powers to be” say let’s put in three chambers tanks.
But they take a 1000 gallon tank and split it into 3!
I would be intersted in comments as well as sites showing plans and standards for sizing according to loadings.
Look forward to replies
24 Apr 2001 at 8:22 am #299688DaveMiller
Gayle: Interesting subject. John’s advice regarding sand contactors is very good. Orenco have a new product called Advantex which is a recirculating textile filter. See there website at http://www.orenco.com for more information.
Regarding the Cook Islands in my opinion a single chamber tank with a good effluent filter is better than chambered tanks.
My website at http://www.davemiller.co.nz covers this area as would the orenco site.
24 Apr 2001 at 11:05 pm #299689SylvanLMP
Thank you Dave
[Edited by John Aldrich on 25 April 2001]
[Edited by John Aldrich on 25 April 2001]
7 May 2001 at 8:42 pm #299690Guest
What is your opinion of the EPA standards for drinking water being applied to waters “effluent” leaving a typical absorption field of a conventional system. To me it seems irresponsible to apply these stringent standards to water that was and never will be utilized for human consumption.
For a little history, I am in Wisconsin and Michigan and these standards are being applied to our new plumbing codes and state laws. I have also been to a few speeches by the primary researcher in the state (UW-Madison) and found his research to be “agenda” driven.
Any comments firstname.lastname@example.org
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