Wastewater treatment for a hotel

[EnOm]

Hi

I am looking for any references on how to size a small wastewater facility for a 10 storey hotel. The system description is as follows:
[ul]
[li]Wastewater from showers and wash basins is collected in a tank in the basement. (Untreated water tank)[/li]
[li]A treatment plant (Pumps, filters...etc) draws the waste water from the tank treats it.[/li]
[li]The treated water is collected in another tank (Treated water tank) [/li]
[li]The treated water is pumped up to a another tank on the roof where it is fed down by a combination of gravity and a booster pump depending on how far the outlet is below the level of the tank.[/li]
[/ul]
I'm not required to get into details regarding the treatment plant itself, I am mostly concerned here with sizing the tanks. What I have in mind is using fixture units to predict the total flow rate from all these outlets. What I am missing though is the storage period required from the 3 tanks involved. Any help is greatly appreciated. Also if anyone could point me to a book or a guideline on the subject that would also be very helpful.

Regards

 

[bimr]

Some things seem to be mixed up. At the present time, I am not aware of any application (except the ISS) where wastewater is being recycled directly into potable water.

The size of the tanks is based on the design capacity of the treatment tank, which is unknown.

There is no reason to have the "Untreated water tank". Wastewater should go directly into the treatment tank. So you can size this tank whatever you desire.

The "Treated water tank" is basically a pump out or break tank. A tank like this is normally sized for 5-10 minutes as a minimum, just to prevent constant pump cycling.

You have not supplied enough information to size the storage tank The size depends on factors such as:

• water demand
• firefighting needs
• capacity of make-up water supply
• contingency reserve
• hot water demand
• hotel size.

http://www.who.int/water_sanitation_health/hygiene/plumbing14.pdf

 

[EnOm]

bimr,
Thanks for your response. I might have not given enough information in my initial post so let me clarify further.
[ul]
[li]The waste water is not recycled into potable water. It is treated to a level where it could be used for toilet flushing ONLY.[/li]
[li]The purpose of the "untreated water tank" is to collect the waste water pending treatment. The treatment system's pumps draw water from this tank directly, treat it, then pump it into the "treated water tank". So effectively it is part of the treatment system. It also allows the collection of waste water to continue when the treatment equipment is being maintained. However, I continued thinking about the topic after posting my question and I am currently considering doing without it and just adding a bypass that takes the grey water directly to the sewer.[/li]
[li]I see your logic regarding the treated water tank being a pump out or break tank. However if I do end up omitting the "un-treated water tank" this tank will become the "treatment tank" where waste water is both collected and treated.[/li]
[li]I shall also do without the roof tank, and instead have a pumping station in the treatment plant room pump directly to the toilets.[/li]
*I got most of these ideas from here:

http://greyter.com/commercial-services/overview-gcw/

What I am considering regarding sizing this tank is to estimate the wastewater flowrate produced by the building then multiplying that with a suitable storage period. Currently I'm leaning towards a 24 hour holding period mentioned here:

http://www.level.org.nz/water/waste...gning-an-on-site-wastewater-treatment-system/

Thank you for your response and any further advice is greatly appreciated


Regards

 

[bimr]

The grey water treatment is just a simple filter, maybe of cloth.

You will have to decide on the particular equipment that you desire to install before you can develop the pumping and storage requirements as the general arrangement of the equipment made by various vendors varies.

You will also have to determine the maintenance requirements so that the area required for the equipment can be established. Some of these treatment systems will call for ceiling heights that are higher than typical.