350L p/min grey water treatment. Need help and input

Good day

Newbie here.  After some input, thoughts regarding designing an organic grey water filtration system using plants for a resort.

I am looking at designing a 80 guest resort.  The resort is located in a remote area with no piped water or sewrage systems.  All the water is trucked in and for 1500L of water from the well cost about $6.25 per trip.

The amount of water I would like to process is 5000L (15 min duration) at peak use that is water from the wash basin, shower and laundry.  Total grey water per day is estimated at 15,000L.

I would like to design a sub surface filtration system using plants to help filtre the water.  Plants will be clumping bamboo, local reeds, bananas and any thirsty type plants.

The plan is to run the grey water through a pre filtre to get rid of the solids before piping it through a ditch 50cm wide by 100cm deep loaded with bamboo, some reeds and bananas.  I've read somewhere that bamboo is quite successful in grey water filtration and where I am living now we have planty of it.  I also heard that friuting plants are also helpful so the plan is to plant bananas purely for ornamental purposes.  The goals is to use the filtresd water for the lanscaping and lawns and any excess water to be used for the aquascape/pond.  Ultimatley I would like to use the water for tiolets which will require some pre filtre and possibly pre treatment and UV treatment.

I have a few questions though reqarding the grey water treatment system.

How deep does the ditch need to be for it to be effective and so that the roots of the plants reach the water to filtre it?

What media should I place in the ditch other than the usual gravel?  I want to keep the system no to low maintainence.  Active carbon in the ditch will require replacement.

How big of a ditch or how much volume does the ditch need to be to process 350L a min or should I say absorb/consume 350L a min at peak.
Regarding area to gallons I'v read that for 1 gallon of grey water will require 1-3sf of land.  i also read that 1 galon require 1 cubic foot. so I am confused as which i should follow.  So if i assume that 1 gallon requires 1 cubic foot it equates to 92 cubic feet (2.6m3) to process 350L.

Is it possible for a ditch 50cm wide by 1m deep to even absorb 350L a min a peak flow?  and roughly how long does the ditch need to be or how much volume is required to process the grey water.
I plan to build the filtration ditch in the car park running along the adjacent wall which is about 50m each wall. Volume will be about 25m3 or equivalent to 885 gallons per 50m length.  If I have two ditches at 50m length (total length of 100m of filtration from start to end total volume will be about 50m3.  What size is sufficient to process 350L a min peak flow.  What will the flow rate of the system be as media in the ditch will down the flow.

We also get torrential rain as well.  Huge down pours.  How will this effect the system.  Will the water overflow out of the ditch? will it be hazardous.  How do I overcome it.  

This has been an idea of mine for while as dumping partially used clean water through a septic tank is such a waste and waste of energy.  I would assume partially used water or grew water is much easier to treat as oppose to black water.

Looking for advice input and ideas as to how feasible the idea is to implement.

Thank you.

Texas law requires a storage tank equal to 3 days of discharge. This is their rain solution, as no puddling is allowed from the system.

Well you can run through the formulas, etc. but generally speaking you want a large enough "Constructed Wetlands" that can contain about 5 days worth of grey water, this is to ensure that the water stays in the wetlands long enough for the plants and bacteria to process most of the BOD.
The gravel is going to take up at least 50% of the containment area, so you'd need something large enough to hold about 150,000L
1 meter depth is fine, but it's gong to need to be a LOT wider than 50cm, probably going to need to be at least 4 meters wide.  Most recommendations say to make the wetlands square, but I've seen some studies that indicate the wetlands that are up to 10 times as long as they are wide work just as well.

Here is a design guide by the US EPA (Design Manual: Constructed Wetlands Treatment of Municipal Wastewater), it's a little conservative in some areas, but has a lot of good info

https://www.epa.gov/wetlands/constructed-wetlands

I am not sure if you are designing the entire resort or a greywater system for an existing facility?  

Could you provide more details on the resort such as existing facilities and/or infrastructure, layout of the resort (type of facilities, number of buildings, cabins etc.), area(s) available for the greywater treatment areas, general topography and elevations of the area, plans for future expansion etc.  Also your location would be useful to understand climate considerations and regulations that may apply.  

The amount of water I would like to process is 5000L (15 min duration) at peak use that is water from the wash basin, shower and laundry.  Total grey water per day is estimated at 15,000L.

 Could you provide information on how you arrived at these numbers?  The peak seems high to me...1/3 of total daily estimate used in 15 min?  The daily estimate works out to around 180 L/guest/day, again this may be a little high/conservative as I am assuming that the necessity to truck in water would result in water conservation priority in design of plumbing fixtures and overall water usage practices at the resort?

If the greywater collection plumbing has not been constructed, it would be worth considering individual at-source treatment systems, provided you are in an area where regulations are not strict or non-existent.  For example:

- Individual or small groups of bathroom sinks/showers directed to small treatment systems comprised of mulch basins
- Laundry facilities could have a dedicated system based on number of machines and expected useage
- Kitchen and food prep areas could have a dedicated system - it would be best to use a mulch/wood chip filter to remove food particles and grease (or a conventional grease trap) prior to discharge to greywater treatment system or any collection plumbing infrastructure.

There are several possible advantages of this strategy:

- You may be able to save significant cost on plumbing materials and installation compared to conventional collection plumbing of all facilities to one treatment area.  
- Each system could be designed specifically for the type of greywater to be treated, and would make planning for daily flow rates and peak events would be simpler, with less risk of over or under estimating the actual flows.  
- smaller easier designs for planning, installation and maintenance - would also be able to be more discretely incorporated into the landscaping plan
- facilitate future alterations to the system as individual areas can be maintained/modified/expanded on a smaller simpler scale.  
- Easier troubleshooting of system issues
- mitigation of system failures.  If a combined system fails, the entire resort is affected, where as individual system failure would only affect those locations where the issue has occured.

Thanks for the replies.

I am not a water engineer or mechanic nor have the necessary documents to prove my legibility on the topic of grey water treatment. So forgive me if I sound to assuming. I have been doing a lot of research and reading on what others have done including some experiments done in Indonesia. Lots of different results out there as they are are all location specific and differ from one country to another.

some background.  We are at looking at building.  The resort will be a 40 room beach front property in Indonesia.  It is two separate building each 2 storey high with a total of 20 rooms each all with shared wall. There will be a pool 25m x 6m x 1.2m depth.  Laundry (300kg per day full capacity x 10litre of water p/kilo) will most probably be done on site, and there will also be a restaurant.
Area is next to the coastline mainly dry with torrential rains during the rainy season. Land is relatively flat however we will be increasing the height of the land on which the building will be located on to around 1.5m.
There is no municipal facilities ie, clean water or sewerage systems
Fresh water needs to be trucked in and the water in the wells are salty and slimy.

What I want to try to achieve is minimum impact on the land, reusing the grey water for landscape, and saving money by using a smaller septic tank for black water (12,000 liters tops).  The grey water that comes from the rooms will be from the faucet/basin and shower which will only be contaminated with soaps, some food particles, coffee, tea, hair, maybe even human by product.

39,300L per day of grey water at 100 occupancy and with each room with having an extra guest (in total 120 in house guest).  I know that this figure might seem out of proportion or large however this figure is like the worst case scenario which I feel that needs to be taken into some consideration when designing a grey water system.


Some Figures
Figures are based on usage per guest is after 7min/L eco shower head @ 15min , 4.5 litre eco flush toilet, 2.5 litre faucet @ 10secs = 2 x shower p/day, 5 times toilet use p/day, 7 time faucet use p/day = 250 litre p/guest.
I budget around 350L p/guest p/day of water consumption just to be safe.
Peak usage would be every guest using the shower at the same time over a 15min period and using the faucet and toilet once during the 15 min duration = 105 litres
105 litre multiply by 40 rooms = 4200 litres
I rounded that figure 4200 litres to 5000 litres just to be safe.

The plan is for a gravity linear fed system by digging a series of connecting trenchs (0.5m wide by 1m depth) that run from the outlet of each building running in front the main corridor which is about 50m in length (help water the landscape) which then connect in the car park area and splits again to run down the length of the car park wall on both sides which will have bamboo and other plants.  the total length is around 200m -250m. The width of 0.5m is not final as this could be made wider to accomodate the grey water treatment system. However if we were to use 0.5m width the total surface area will come to about 100m2 min with a total volume of 70m3 if depth of total drainage and filter material is 0.7m

The trench shall be filled with media. Starting from the bottom 20cm of course gravel or large stones, a layer of landscape cloth, 20cm of sand, a layer of landscape cloth, gravel 30cm, a layer of landscape cloth, 30cm of top soil and topped of with 15cm of large pebbles for aesthetic purposes. total drainage material height is 70cm in depth however is not final depth.

Back to the system handling 5000 litres of water in 15min or 333 litres per min, the water shall drain into the gravel base first from the outlet side of the building.  Since waters travel in the direction of least resistance I assume a gravel depth of 0.3m x 0.5m wide by 200m length (30m3) should be sufficient to absorb the water and give it more than enough time to percolate through the sand layer.

I have yet to perform a percolation test which plan to do in the coming weeks by making a acrylic/plexi glass box 20cm x 20cm x 100cm depth.

My concern now is how effective is the depth of filter and drainage material in the trench at filtering out the grey water.  How safe or clean will the end product likely be.  Will it be safe to release into the ground, or safe to use for watering the lawn.

How much of a difference or how much cleaner is the grey water if it travels the length of the entire trench.

Will it even be effective way of treating grey water or just a waste of time and money based on the depth of layer of filtration material as stated above.

Is the size in area and volume sufficient for treating the water to acceptable levels.

I hope I have provide enough details.  I will try to upload a plan of the site and where the proposed trenchs will run.

Thanks for reading this post.  Please feel free to correct me if i am wrong of if you feel that I've overly speculated on some of the figures.  



   

Peter VanDerWal wrote:Well you can run through the formulas, etc. but generally speaking you want a large enough "Constructed Wetlands" that can contain about 5 days worth of grey water, this is to ensure that the water stays in the wetlands long enough for the plants and bacteria to process most of the BOD.
The gravel is going to take up at least 50% of the containment area, so you'd need something large enough to hold about 150,000L
1 meter depth is fine, but it's gong to need to be a LOT wider than 50cm, probably going to need to be at least 4 meters wide.  Most recommendations say to make the wetlands square, but I've seen some studies that indicate the wetlands that are up to 10 times as long as they are wide work just as well.

Here is a design guide by the US EPA (Design Manual: Constructed Wetlands Treatment of Municipal Wastewater), it's a little conservative in some areas, but has a lot of good info

https://www.epa.gov/wetlands/constructed-wetlands

Yeah we dont have the land for Constructed wet land. We only have 7500smq.  I did have an idea of filling up the parking lot with a layer of gravel and sand  .5 - .8m in depth.  Parking lot is 400 sqm which would be about 200m3 volume.  The water would just percolate into the soil beneath. I just want to be sure that I am not polluting the land and want to be sure whether the intial filtering through the gravel and sand was sufficient enough to bring the grey water up to safe levels.  Or whether this route is no the right solution  or whether there should be some pre-treament first.

Thanks for the input.  

Great Point

There are several possible advantages of this strategy:

- You may be able to save significant cost on plumbing materials and installation compared to conventional collection plumbing of all facilities to one treatment area.  
- Each system could be designed specifically for the type of greywater to be treated, and would make planning for daily flow rates and peak events would be simpler, with less risk of over or under estimating the actual flows.  
- smaller easier designs for planning, installation and maintenance - would also be able to be more discretely incorporated into the landscaping plan
- facilitate future alterations to the system as individual areas can be maintained/modified/expanded on a smaller simpler scale.  
- Easier troubleshooting of system issues
- mitigation of system failures.  If a combined system fails, the entire resort is affected, where as individual system failure would only affect those locations where the issue has occured.


Something I did consider was having a valve that i could direct the grey water to the septic as back up.  But that means I would need a larger capacity septic.

What area of Indonesia.  I spent 3 years there.  I sent you a PM with some contacts that are involved in the types of development you are considering, they all happen to be based in Bali, but they likely have contacts in other regions as well.

P Lyons wrote:What area of Indonesia.  I spent 3 years there.  I sent you a PM with some contacts that are involved in the types of development you are considering, they all happen to be based in Bali, but they likely have contacts in other regions as well.

Small world.  We are looking to build on an island next to Bali called Lombok. I just went through and checked all my calculations again.  I put down 15 min while the average show time is between 7-10 mins.  So that made a huge difference in the water usage.  Plus the room do not have bath tubs so no wasting water there. So it comes in at 250 L per person.

The way hotels count their water consumption per room is based on the occupancy, a king room with single occupant as to a king with 2 occupants.  In that scenario you would base the water consumption on 1.75 times occupancy mulitply by the average percentage room occupancy rate per month.

However in my case its a little different.  Sure I can calculate base on assumptions and target however what is certain is the hotel will most likely be operating at full occupancy plus extra guest once in a while.  Which means its better to take in account the peak rate and design the system around those figures.

Peak water usage comes in at 29,800 Litres grey water and 9000 litres black water.


I am little concern of channelling all the grey water into a subsurface type filter.  Whether the water will be safe for the environment.  I believe the size of the trench and volume is more than capable of absorbing 3000Litre in 10 min and handling the rest of the 27,000 litre of water through put the day.  

I better talk with your contacts.  Cheers for the head up.

heya.... would it be possible to divert the blackwater from the greywater?
by using urine diverters and male urinals (duct into the greywater) you might reduce the amount of blackwater even further.

there s a system (there are posts here on the forums) where the black water drops into a container with woodchips and compost worms. after that the water could be treated by a sedimentation chamber or swirl filter and the a reed-bed (or go directly into your greywater system).

i think, a long and narrow ditch/trench along the perimeter of your estate would be a good thing for the greywater. and and multiple small units (a pond/wetland with trees, reeds, bamboo etc.)

Tobias Ber wrote:heya.... would it be possible to divert the blackwater from the greywater?
by using urine diverters and male urinals (duct into the greywater) you might reduce the amount of blackwater even further.

there s a system (there are posts here on the forums) where the black water drops into a container with woodchips and compost worms. after that the water could be treated by a sedimentation chamber or swirl filter and the a reed-bed (or go directly into your greywater system).

i think, a long and narrow ditch/trench along the perimeter of your estate would be a good thing for the greywater. and and multiple small units (a pond/wetland with trees, reeds, bamboo etc.)

I keep hearing about using wood chips.  Would this be the first stage of the system whereby the grey water enter first, gets filtered by the wood chip and mulch and earth worms (would the grey water be safe for earth worms?)

I am thinking of combining the idea of subsurface CW with wicking bed though I think the principles of both systems are relatively the same.

yes, grey water is ok for worms. but get composting worms. they do better in that situations. it s a very good treatment of the solids form black water.

but if possible, try to divert grey water from black water. and direct urine into grey water. it would be a bit more complicated to plan and install. but you ll have a small and super efficient system for black water then. but the majority of the (more unproblematic) greywater will go through a bigger and less intense system.
greywater is not that problematic. you could just use tubing and put that directly under trees and bushes...

here are some links:

https://permies.com/t/17877/Humanure-flushing-toilets-worm-farms

https://www.permaculture.co.uk/readers-solutions/how-make-vermicomposting-flush-toilet

Yeah I dont think it would be possible to direct the urine into the grey water system unless we have a separate urinal and closet.  

Any take on the trench idea/ wicking bed/ subsurface CW? If grey water is kept in the threshold of the resevoir (gravel layer) will it habour more disease and bateria and cause the water to smell?  The only time the water will over flow is if the water level rises.  The water in the the reservoir would be able to supply surface plants water just like a wicking bed whilst purifying the water.

Currently checking out grey water action org and lopking for details on mulch basin design and how to prevent clogging of system.