STEP sewer system 3

[jartgo]

Could anyone point me in a direction of some good info on the subject systems. I figured I'd see what I can learn before asking specific questions.
Thanks.

 

[RWF7437]

Google "Environment One".

good luck

 

[francesca]

Try this:

http://www.orenco.com/

 

[BarryEng]

Have a look at

http://www.epa.gov/ord/NRMRL/pubs/625191024/625191024ch2.pdf

for a 65 page (chapter 2) doc of pressure systems.
Very good set of refs at the back.

Also do an internal search (of the EPA USA web site) for : - EPA62519104.
EPA - the organisation
625 - research I think
91 - year of publication
04 - fourth pub for that year.

This is a 220 page pub titled Alternative Wastewater Collection Systems.

That lot of reading should do you for the next week or two.

BarryEng

 

[BarryEng]

I thought that you may have trouble finding the site & pub (Alternative Wastewater Collection Systems) etc.
Here is the link

http://nepis.epa.gov/Exe/ZyNET.exe/300046DW.txt?ZyActionD=ZyDocument&Client

=EPA&Index=2000%20Thru%202005%7C2006%20Thru%202010%7CPrior%20to%201976%7C19
76%20Thru%201980%7C1981%20Thru%201985%7C1986%20Thru%201990%7C1991%20Thru%20
1994%7C1995%20Thru%201999%7CHardcopy%20Publications%7COnline%20Publications
&Docs=&Query=Septic%20tank%20effluent%20pumping&Time=&EndTime=&SearchMetho
d=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDa
y=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=%5C%5CNEPIS%5FLIB
2%5CD%5CZYFILES%5CINDEX%20DATA%5C91THRU94%5CTXT%5C00000002%5C300046DW.txt&
User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=15&Fuz
zyDegree=0&ImageQuality=r85g16/r85g16/x150y150g16/i500&Display=hpfr&DefSee
kPage=x&SearchBack=ZyActionE&Back=ZyActionS&BackDesc=Results%20page

Sorry about the length, but it works for me.

BarryEng

 

[Spartan5]

Excellent information Barry!

I have not read that first document in its entirety yet, but having designed STEP systems for several years, I can attest that it looks very useful and thorough. From what publication is that chapter taken?

While we are on the subject (and if anyone thinks this should be discussed in its own thread let me know)... The matter of design flows.

From Barry's doc:

Fundamental to the design of a sewer system is the determination of design flows. Where actual flow characterization data are available they should be used. An allowance of 380 L/cap/d (100 gpcd) has been used as a general rule in the design of conventional sewer systems However, that general rule may allow for more infiltration than may occur when pressure sewers are used, and it allows for some amount of commercial and industrial use that may not be present in pressure sewer design. Experience with pressure sewerage has shown a lower allowance to be more in order.

During the early stages of pressure sewer development extensive investigations were made into domestic water consumption during periods of low outside water use, with the correlation that water consumption would closely parallel sewer flows. These studies showed flows of 150-230 L/cap/d (40-60 qpcd). Flow measurements were made on conventional sewers serving residential communities during periods when l/l was not occurring, with the same conclusions.

At this time, thousands of flow measurements have been maden pressure sewer systems with wide demographic spreads. The result of these measurements has corroborated findings of the earlier studies; that flows are typically 150-230 L/cap/d (40-60 qpcd), with little weekly or seasonal variation.

The availability and quality of water affects water use and consequently sewer flows, as does water pressure, community affluence, nature of occupancy, and attitudes of the users regarding water conservation. Because of these variables and to provide a safety factor, the flow rate normally assumed for design is 190-265 L/cap/d (50-70 gpcd).

While pressure sewers are sometimes Thought to be free of l/l, it can occur in the non-pressurized portions of the system, e.q., the building sewer and the tank. In some cases l/I has been extreme, due to leaking building sewers or house roof drains being connected to the building sewer, due to pump vault risers being set below ground level which allows surface water to enter, or in the case of STEP systems due to leaky septic tanks. It is prudent to make an allowance for l/I when a design flow, based on the extent of l/l control given to the project.

I always have a struggle here in MI regarding the basis of desgin during the permitting process for STEP collection systems and the associated treatment works for small communities (10-250 homes). They require us to use 100 gpcd (300 gpd/unit). This does not cause a big change in the design of the collection system, but it results in many other problems. The treatment system if often significantly larger than it needs to be; or the client is limited to the number of lots they might have by site constraints; or the client has stipulations placed in their permit that they may only build so many homes until they have proven the less conservative basis of design.

Multiple sources recommend design flows rates of 50-70 gpcd with actual flow rates of 40-60 gpcd. All of the data I have seen that those numbers are based on were collected before 1994 before EPACT mandated low-flow fixtures in new construction.

I think that some lifestyle changes may have possibly offset the savings of the low-flow fixtures. In the systems we monitor, 40-60 gpcd is typically what we see. Even with some infiltration.

If anyone has any current studies on the basis of design for STEP systems please share. I am seeking as much information as possible (studies, publications etc). Arrows in the quiver if you will.

And on a related note to the original question. One of the works cited in BarryEng's doc was Design and Use of Pressure Sewer Systems by David Thrasher.

http://www.amazon.com/Design-Use-Pressure-Sewer-Systems/dp/0873710703/

I used the "search inside" feature to read a chapter of it and it looks to be a useful reference. I've got a copy being transfered from a distant library and I'll share my thoughts on it when I've had a chance to peruse it.,

 

[Spartan5]

BarryEng:
Never mind my question regarding the source of the PDF you posted. I see it is from the second document you have shared.

 

[BarryEng]

Spartan5
I'll bet that the link that I submitted above has got to be the longest that has been posted on the eng-tips web site. A search of that site (EPA USA), will result in the most amazing quantity of reports, manuals of practice, design systems, etc that has has ever been posted on the web in the field of 'environmental subjects.'

Have a look at the complete list of pubs on the EPA USA web site. Look in the 625 area for your subject. Of interest to me was the 'onsite treatment & disposal of wastewater' (I think that is the title - septic tanks originally but now expanded to cover SBR's etc etc.). The original doc was in the early 80's but has been updated to 2004 I think. This has got to be one of the most comprehensive texts of this subject.

Only one better reference was a book that I have on 'septic tank practices' that is a gold mine of info (& compulsory reading) if you are arguing a case for the use of other alternatives to the 'big sewer'. You must remember that 25% of USA is served with septic tanks for wastewater. So if centralised wastewater is the only answer for waste water treatment, 25% of the population of the USA would have to move off shore.

I still have the earlier edition because it has a selection criteria of effluent disposal which is excellent. In it you look at the site slope, soil conditions, soil types, proximity to bedrock, proximity to ground water etc etc. It has a matrix of results such as leach drain, french drain, mound system, etc etc.

By the way, I am a water engineer in the field of water retaining structures & pipelines. Wastewater is only a passing interest to me because that is what I originally designed when I first qualified (a hundred years ago).

BarryEng

 

[jartgo]

Thanks for the info, I got sidetracked looking at all the other documents that are available there.

Just to clarify in case anyone else is looking for it, the document number is actually "625191024" as listed in the link above.

The search page is:

http://nepis.epa.gov/Exe/ZyNET.EXE?...nonymous&Password=anonymous&Client=EPA&Init=1

Thanks again.

 

[RWF7437]

Spartan5,
Yes, please do start a new thread .

 

[BarryEng]

Sorry about the incorrect info.
More haste, less speed.
As "jthompson" said in his info above, the correct number is 625191024. Going back to my first reference, 024 appears in the email reference address, but I did not copy it correctly in the next para. The 024 means the 24th pub in that year (91) in the area of 625.
The figure 1 following 625, is the research area (I think), followed by the year of pub - 91.
Several years ago, the reference would have been EPA 625R/91-024, & I suppose it changed to the present format to aid searches using the numerals only.

BarryEng