UKTC Archive

Re: Biodisc effluent - impact to trees?

Subject: Re: Biodisc effluent - impact to trees?
From: Wayne Tyson
Date: Dec 22 2017 22:12:08
Maybe I missed it, but I didn't catch what kind of trees you are using or
if it is being discharged onto indigenous species or just how it is being
discharged (below the surface, on the surface, by sprinklers, or ditches,
or just released at some point).

All organisms change in response to changes. The safest assumption is that *as
long as* one is mimicking the range of natural conditions under which the
trees (or other organisms) evolved, you might be in a safer than a more
dangerous zone . . .  If, and to the degree that one exceeds that range,
one is more likely to run into trouble. Just one of an infinite number of
possibilities: If one is discharging treated effluent continuously,
saturation becomes more likely, depending upon the underlying soils and
geology. That can lead to slope failure and/or luxury conditions that could
cause some trees to grow faster, which, in some species, could lead to
weaker limb and trunk structures, which could induce premature structural
failure. Any "surplus" (greater than ETo) water will end up flowing through
the geologic structures, which will react accordingly. There is more to
treated effluent than, say, BOD, pH, and dissolved solids (hormones,
toxins, metabolic products, ad nauseam) and these may not be subject to
"cleansing" or "filtering," two popular myths that plague this subject (did
I mention plagues?).

Nothing beats analysis of all relevant factors and specific information.
"The more you generalize about a population, the less you know about any
individual in that population."  --Henry Geiger

A lot depends upon the ability of those carrying out actions to correctly
synthesize the information and to avoid assumptions or conclusions based on
"intuition" or traditional beliefs.

In the absence of such details, any presumption would be irresponsible, but
if I were forced to conjecture on the basis of the few facts provided, it
would probably be that there is a greater than even chance that whomever
does this is cruisin' for a bruisin'. Of course, the adverse effects of
acting on flawed decisions in such circumstances can take a very long time
to become obviously disastrous, meaning that the guilty parties may be long
gone by then, and innocents will be the ones to suffer. In other words, one
might get away with it! In other words, it sounds like a bad idea in
general, but it could be "good," depending on the context. And context is


On Fri, Dec 22, 2017 at 1:04 AM, Igoea, Andrew <> wrote:

Thanks for all the responses to this.

To clarify, its treated effluent entering the soil through a soak away
type of arrangement rather the application raw sewage to the surface.

To summarise:
- Tree species have a natural range of soil conditions which they are
suited to
- The trees on this site will have grown and adapted to the soil
conditions present and will be able to cope with natural variations in soil
moisture, pH and other soil properties.
- The question is whether the effluent will create conditions beyond the
range that the trees can cope with
- The anhydrous ammonia is likely to increase the levels of N in the soil
and lower the soil pH
- The quantity of effluent entering the soil will increase the soil
moisture content and may lead to anaerobic conditions.
- All these changes to soil properties could impact fungi, soil
microbiology and fauna
- The impact to fungi includes a potentially detrimental impact to
mycorrhizal fungi associations, key to tree health.
- Anaerobic soil conditions could lead to root dieback, leading to crown
dieback, leading to safety concerns and an impact to amenity value.
- Root dieback and decay, resulting in degradation of tensile strength in
structural roots could lead to an increased risk of uprooting
- Increased soil moisture could also increase the risk of uprooting to due
to the reduced shear strength of soils around/beneath the root plate

Anything else??

-----Original Message-----
From: [mailto:uktc-request@lists.] On Behalf Of Igoea, Andrew
Sent: 21 December 2017 10:20
To: UK Tree Care
Subject: Biodisc effluent - impact to trees?

Hi All,

Has anyone had experience with assessing the impact of discharging biodisc
effluent (treated sewage) into the rooting zone of trees?

The treated effluent will contain 10mg/L suspended solids and 3.8mg/L
ammonia, and will have a BOD of 10mg/L. The output could be between 1-2
cubic metres per day.

The treatment facility is at the top of a steep bank and the trees are
below it.

I know the proposal will impact the moisture content and chemical
composition of the soil, which could impact the mycorrhizal associations
and soil fauna, but will it have a significant detrimental impact on the


Andrew Igoea  | Arboricultural Officer
Forestry, Amenity and Lands Directorate | Department of Environment, Food
and Agriculture
Thie Slieau Whallian | Foxdale Road | St Johns | Isle of Man | IM4 3AS
TEL:  (+44) 01624 XXXXXX | MOB: (+44) 07624 XXXXXX | E-MAIL:<>

Isle of Man. Giving you freedom to flourish

WARNING: This email message and any files transmitted with it are
confidential and may be subject to legal privilege. You must not copy or
deliver it to any other person or use the contents in any unauthorised
manner without the express permission of the sender. If you are not the
intended addressee of this e-mail, please delete it and notify the sender
as soon as possible.

No employee or agent is authorised to conclude any binding agreement on
behalf of any of the Departments or Statutory Boards of the Isle of Man
Government with any party by e-mail without express written confirmation by
a Manager of the relevant Department or Statutory Board.

RAAUE: S’preevaadjagh yn çhaghteraght post-l shoh chammah’s coadanyn erbee
currit marish as ta shoh coadit ec y leigh. Cha nhegin diu coipal ny cur eh
da peiagh erbee elley ny ymmydey yn chooid t’ayn er aght erbee dyn kied
leayr veih’n choyrtagh. Mannagh nee shiu yn enmyssagh kiarit jeh’n phost-l
shoh, doll-shiu magh eh, my sailliu, as cur-shiu fys da’n choyrtagh cha
leah as oddys shiu.

Cha nel kied currit da failleydagh ny jantagh erbee conaant y yannoo rish
peiagh ny possan erbee lesh post-l er son Rheynn ny Boayrd Slattyssagh
erbee jeh Reiltys Ellan Vannin dyn co-niartaghey scruit leayr veih
Reireyder y Rheynn ny Boayrd Slattyssagh t’eh bentyn rish.

The UK Tree Care mailing list
To unsubscribe send

The UKTC is supported by Bosky Trees arboricultural consultancy

The UK Tree Care mailing list
To unsubscribe send

The UKTC is supported by Bosky Trees arboricultural consultancy