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Waste water treatment

11/28/2008 11:23 AM

I am been assigned the task of designing a waste water treatment system for an apartment complex of 75 flats at peak will house 300 people. I have to make some educated guesses about flow rate & quality of effluent and also decide on a cheap system which is easy to maintain.

Based on experience I have arrived at a flow rate of 80m3 per day with an average BOD5 of 200 mg/L. The treatment I have in mind is fully anaerobic. After the equalizer tank and the digester I have plans to employ a further treatment by way of a chlorine dosing pump, pressure sand filter and an activated carbon filter and finally water will be released to a nearby water stream.

My main concern is the sizing of the anaerobic chamber and would appreciate your valuable input on correct design size without over/under designing. I also would appreciate to receive your comments on my assumption on rate & quality of the effluent and also th type of treatment.

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#1

Re: Waste water treatment

11/28/2008 1:01 PM

A BOD loading of 200ppm can easily be treated aerobically. After separation of the solids, approximately 6 - 8 hours of aerobic treatment will breakdown the BOD and nitrify the ammonia quite nicely. Add 2 hours of anoxic treatment, and another 4 hours of secondary aerobic treatment, and you will not only have broken down the BOD, you'll also have removed the nutrients from the water, an important point to consider since the effluent is to be discharged into a stream. In many parts of the world, discharging nutrient-rich effluent is an environmental violation since it can cause eutrophication.

Here are some other points to consider. Anerobic systems are extremely slow: you'll need between 15 to 60 days of retention to effectively digest the wastes depending upon the reactor temperature. You'll also need to provide a lime or caustic soda dosing system in order to maintain a pH level between 6.5 and 7.5, otherwise your desired methanogenic bacteria will die and lead to the growth of undesirable bacteria that will release foul smelling gases like hydrogen sulfide and ammonia. Anerobic digestion is also incomplete and will still require further aerobic treatment to breakdown the wastes completely, otherwise they will impose a severe BOD loading upon the receiving waterway. Their chief advantage is that they can breakdown high strength wastes at low cost, and can produce valuable methane gas for fuel at the same time.

Anyway, here is the information you are looking for from Metcalf's & Eddy's Wastewater Engineering.

Anerobic contact process, 2 - 10 hours detention, input COD 1,500 - 5,000ppm, organic loading 0.03 - 0.15 lbs-COD/ft3.day, removal η 75 - 90%

Upflow anerobic sludge blanket, 4 - 12 hours detention, input COD 5,000 - 15,000ppm, organic loading 0.25 - 0.75 lbs-COD/ft3.day, removal η 75 - 85%

Fixed bed, 24 - 48 hours detention, input COD 10,000 - 20,000ppm, organic loading 0.06 - 0.30 lbs-COD/ft3.day, removal η 75 - 85%

Expanded bed, 5 - 10 hours detention, input COD 5,000 - 10,000ppm, organic loading 0.30 - 0.60 lbs-COD/ft3.day, removal η 80 - 85%

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#2
In reply to #1

Re: Waste water treatment

11/28/2008 10:37 PM

Thank you. I know you have been giving valuble advise through CR4 for some of my earlier posts too.

The composition is typical domestic waste from toilets, bathrooms & kitchen sinks. I thought aerobic will be risky as waste contain human excreta.

I thought 5 days retention would bring down BOD by 80% in 5 days, am I wrong?

In your data you stated anaerobic contact process 2-10 hrs detention removal eff as 75-90%. Can you pl explain?

Thanks again.

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#3
In reply to #2

Re: Waste water treatment

11/29/2008 1:22 AM

Hello Sisira:

What DVader1000 is some good advice.

When you say you have to design a system, you realise this can hardly be done at less than a certain minimum price. You cannot cut corners with this kind of thing. And a certain amount of 'over design' is preferred to any amount of 'under designing, and its consequences!

I have found a site which may be of use as it describes what reactions happen and what needs to happen to the waste at each stage.

The diagrams are a little primitive but hopefully adequate.

Why cannot the flows flat the building go to a treatment works, which treat effluent from millions of people, not just 300.

This seems like a very expensive way to deal with the waste. And, it will need to be some distance away and down-wind.......If you get my drift? Is it not feasible to have several large Cesspit's which are emptied very regularly? The 'clients' living in this build or complex need know anything of this. I think they would have more interest in decorating than 'poo'.

Good luck anyway.

======================================================

This is how three types of system work and should be set up in detail.

http://en.wikipedia.org/wiki/Anaerobic_contact_process

Anaerobic contact process

From Wikipedia, the free encyclopedia Jump to: navigation, search

The anaerobic contact process is a type of anaerobic digester. Here a set of reactors are created in series, often with recycling. This recycled material is pumped up into the bottom of the first reactor, an upflow reactor. The upflow anaerobic process is a large reactor which allows the waste to flow up from the bottom and separates the waste into 3 zones. At the very top is the biogas zone where the gas is collected. Bacteria digest waste in the lowest portion of the upflow reactor; the bio-reactor zone. In between these two stages is the clarifier zone where the which exports the stabilised waste [1] [2].

A diagram of an anaerobic contact process can be found here.

[edit] See also

References

  1. ^ Owen, William F. (1982) Energy in Wastewater Treatment. New Jersey: Prentice Hall, Inc.

This waste-related article is a stub. You can help by expanding it.

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Retrieved from "http://en.wikipedia.org/wiki/Anaerobic_contact_process" Categories: Anaerobic digester types | Waste stubs

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#4

Re: Waste water treatment

11/29/2008 3:21 AM

hi bro I am working as an engineer ( Plumbing & Fire Fighting) in one of the biggest shopping mall in india . We have planed Sewerage Treatment Plant (S.T.P) for 10,000 gallons of waste water if u need its detailed drawing of the same , I will provide u . The complete technical details,specification will guide u in ur project. my email address is:-bawa333us@yahoo.com,bawacanada@gmail.com

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#5
In reply to #3

Re: Waste water treatment

11/29/2008 8:08 AM

Hello babybear, thanks a lot. The information is great. This plant is for a resort area. They do not have a waste plant for large population. That is why each building has to have its own waste water treatment plant. For domestic (for individual houses they allow a simple digester/septic tank. But since this is a 75 housing unit complex we need to have a plant. Do you have any idea of retention time I should allow for in the process. I know this can vary from process to process. Just a guide line will be helpful in sizing the units.

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#6

Re: Waste water treatment

11/29/2008 9:51 AM

There is a system on the market that will acheive everything you desire, including the gasification of solids that will eliminate the anerobic digester entirely. I wonder where you are located, because having to develop this system from scratch will be very expensive. Are there other residential units in the area that could combine their effluent output to be able to afford a complete system with a minimum flow of 250Gal/day (do the conversion math.) This system is totally self contained and will produce effluent that meets California Class 22 discharge requirements. The effluent can be discharged into a stream, depending on your local requirements. Go to www.mmmfwater.com. Tell them Dan from Michigan sent you.

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#7
In reply to #6

Re: Waste water treatment

11/29/2008 11:06 AM

Dan, Actually I am from Sri Lanka a small island near India, known for beautiful & sunny beaches,aromatic Ceylon tea, Blue sapphire Gems and friendly people and also a ferocious terrorist group called LTTE tigers who kill innocent people & recruit child soldiers. We produced 1st lady prime minister of the world and LTTE is infamous for producing the 1st suicide bomber of the world. Perhaps you may have heard of our country more due to the latter! So enough about Sri lanka. My estimate is we will have to treat approximately 80m3/day , way above 250gal/day! anyway i will go to the web site and have a look!

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#8

Re: Waste water treatment

11/29/2008 11:27 AM

I like to discuss your basic assumptions.

1. 80 m3 per day for 300 persons makes it 266 Liters/day. The EU estimate per person is about 150 Liters/day. Here in Israel it is about 120 Liters/day. Are you sure?

2. BOD of 200 seems tome as too low. 600 - 800 make more sense to me.

What is your opinion?



What is your opinion?

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#9
In reply to #8

Re: Waste water treatment

11/29/2008 11:57 AM

Hi Monami, Yes. I agree on the rate, it is a bit over rated. Being a holiday resort though official capacity is 300 persons (4 persons /flat of 2 rooms) I expected at peak time may be we can expect average 6 persons per flat. on the BOD I used figures from Page 186- table 3-15, Wastewater Engg by Metcalf & Eddy. Is your figure based on experience?

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#10
In reply to #8

Re: Waste water treatment

11/29/2008 6:37 PM

Hello monami:

I thought the estimates were pretty low myself. I mean, you may have a home designed for 3 or 4. Doesn't mean there may not be at least 6 or more. Are these people not going to have 'Guests' round, or have no parties?.............Take no baths or showers?

I know he mentioned keeping the cost down, but, I would ask any locals how much they use then double it! What about rain water? How are they going to keep that out. All drains let it through and a dam sight more than 25/300 litres a day when it is raining!

I said about it and a couple of others have said it is going to be ssooooo expensive to have a full plant for only 75 houses? They would have to be millionaires to afford to live there. .................Just imagine it, "oh hellow dear, I hear you live next to the sewage farm"? No No NO NO NO!!!!!

No offence to the OP but, he has no idea how much ground-work has to be completed for this system. It will make the house building seem insignificant for sure! And, why can't the local 'council' or whatever they are called in the States build a 'proper' system and charge everyone who wants to link to it like in the UK?

I would not fancy a sewage plant near me. We had one almost 4 Km away and still got the smell when the wind was in the wrong direction. I doubt very much the OP has plans to build his plant that far away from these houses. Why can't other nearby residence pay to get hooked up to a full blown sewer plant serving say 50,000?

Everything I have heard so far says 'short cut', to making a quick buck!

Take care.............

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#11

Re: Waste water treatment

11/29/2008 6:52 PM

Hello Sisira:

I sent you via my post maybe 50 links. Why not read those and find out how long it takes for s-it to disappear?

What Country are you building this?

No offence to you but, you have no idea how much ground-work has to be completed for this system. It will make the house building seem insignificant for sure! And, why can't the local 'council' or whatever they are called in the States or where you are designing this, build a 'proper' system and charge everyone who wants to link to it like in the UK?

I would not fancy a sewage plant near me. We had one almost 4 Km away and still got the smell when the wind was in the wrong direction. I doubt very much you plan to build his plant that far away from these houses. Why can't other nearby residence pay to get hooked up to a full blown sewer plant serving say 20,000/50,000 people? Explain to the Money Men, the 'Suites' there is money in muck! And plan to build a larger one.

I will check on the time it takes for the bugs to work. But, from what I know and have read it can vary a lot.

Take care, and sorry for the rant.

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#12
In reply to #4

Re: Waste water treatment

11/29/2008 6:57 PM

Hello bawa333us:

It sounds like the OP can do with some help! And yours I am sure will be very good.. I know he is under estimating the building of the sewer works, and has no idea how much groundwork it takes.

Take care..................

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#13

Re: Waste water treatment

11/29/2008 7:35 PM

Hello Sisira,

I have just read the posts again and it seems DVader1000 has already answer the question of 'retention' you asked me.

Have another look at DVader1000's post and study the figures against what you find on-line with any links given by other or by me and all will become clear.

Allow me to say this please..................If you cannot find or know how long it takes for the 'stuff' to be retained, maybe you should say, "thank you, but, no thanks" to whoever it was requested you to biuld this plant.

That was not meant in a hurtful way. But, .........

1) You must know how much waste a set number of dwellings are likely to produce.

2), You must build this plant further than a 'stones throw' away!

3) The design of the plant decides how many beds you have and the design of those beds.

4) Apart from having to build it some way from the homes, depending on how far will increase the cost.

5) But not building it far enough away will leave you personally open to some lawyer screwing you for your mistake.

6) A plant for a set number of people, depending on the type of retention, all plants should cost about the same.

7) The 'costs' are not something you can cut corners with AT ALL!

8) I would not have thought of building a sewer plant for so few dwellings and or people.

9) The cost will be astronomical.

10) Why not get an expert in to design and build this if you have to go ahead with it. Then if something goes wrong, HE is the one with a lawyer round his neck?

....................Take a look at DVader1000's figures and do some research, so you have some idea of the job you have to do, or the job you have to design. If you had designed something like this before you would not be asking for advice now, right? So get your head round the figures and alternative designs and other options, apart from a full blown sewer plant....................Lets put it this way; given the choice I would use several of the largest cesspit's and pay on a contract for someone local to empty them. I am pretty sure it will be less of a headache that paying for a half a dozen people to run the sewer plant full time.

I give this advice in sincerity. And I am not moaning at you.

Good luck.........

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#14
In reply to #6

Re: Waste water treatment

11/29/2008 7:40 PM

Hello Yooper1946:

I cannot get to this link you posted. But it sounds like just the thing for the OP?

Thanks...........

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#15
In reply to #1

Re: Waste water treatment

11/29/2008 8:15 PM

Hello DVader1000:

/approximately 6 - 8 hours of aerobic treatment will breakdown the BOD and/ nitrify the

I do not think the OP read or perhaps understood your post, as he asked me about how long the retention should be, or similar stuff?

I told him to study your detailed post very much ON TOPIC! And a GA is on its way. Thanks.

It is hardly 'Tea-Time talk', but, non the less very interesting..........But, then I am letting my foibles out there, oops!...................Better put 'em back in.......

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#16
In reply to #2

Re: Waste water treatment

11/30/2008 2:02 AM

Q 1. Actually, aerobic will be safer for treating human excrement than anerobic. This is because pathogens are evolved the survive in the anerobic environment of the human gut. Aerobic treatment creates an environment that the pathogens cannot survive in. Anyway, for further safety, before discharging the effluent, you should disinfect the water using UV, ozone or chlorine to ensure that all pathogens are killed off.

Q2. The longer the detention time, the more efficient the BOD removal process is. But take note: 90% BOD/COD removal efficiency still leaves 10% behind, and 10% of 15,000ppm is still 1,500ppm.

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#17
In reply to #15

Re: Waste water treatment

11/30/2008 2:03 AM

Thanks for the GA. You got one from me too for the extremely detailed description of the anerobic reactor.

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#18
In reply to #16

Re: Waste water treatment

11/30/2008 2:38 AM

Hello DVader1000:

Good point there, even at max efficiency there will probably always be 10% of waste which is essentially untreated.

I am not sure if the OP really knows what a hole he is in? Put a house up in a few days. A sewer plant is serious engineering, and I do not think (you know who) realises that.

I like the bit about cutting costs? Well, again to some extent you can do that on dwellings, smaller windows is just one obvious cut. Can't really do that with a sewer. It should be done correctly, or not at all. I still think some large cesspit's emptied everyday is a much better answer.

The best way will be the most expensive but will clean the nasty stuff about five times faster and that in the 'Anerobic contact', and the 'Expanded bed', but thay aint cheap.

This gives an Estimate but I am not sure how up to date it is.

http://books.google.co.uk/books?id=G4tT0ESKVpUC&amp;pg=PA10&lpg=PA10&dq=Expanded+bed+sewer&source=web&ots=bD9tialY-Z&sig=sEgDJUHMboz75KDFCdUDKTTFW8s&hl=en&sa=X&oi=book_result&resnum=1&ct=result#PPA13,M1

But, then, if the local Government care so much for its people why do they not have a sewer system? And with ref' to that same Gov', where will they allow the discharge of human, or any waste for that matter?

Bad deal all round for me.

Was it Spain this is happening? Remind me not to go to Spain again OK?

Take care.................

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#19
In reply to #14

Re: Waste water treatment

11/30/2008 6:38 AM

I am not sure why you are having a problem linking. I just Googled it, no problem. Just to make sure, it is www.mmfwater.com give it a try one more time. If it does not link, google it. I did not get a direct link, but it was on the top of the page. Click on Home, then take a good look. I was at the Woodsville, New Hampshire, USA demonstration site on Nov. 24 '08. They are getting test results better than required by the New Hampshire water quality standards. This system is disruptive technology and faces a hard battle to overcome the closed minds of the engeering firms that get paid to lay down pipes, concrete, and valves. This system will process 1M gal/day inffluent, with effluent meeting any state or EPA standards. The total energy requirement is only 10 Hp, which can be produced by the gasification of solids(Totally green). What is amazing is that the entire system only uses a 2,000 Square Foot footprint. The cost of construction is much less than conventional systems. The cost of operation and maintainence is drastically reduced. The system can be configured to meet almost any flow rate, it is not limited to the above mentioned 1MG/day. The New Hampshire plant is totally enclosed to provide year around operation at consistent temperatures, so cold weather locations are not a problem. The energy to heat the building can be produced by the system. The most pleasant thing is that there is almost no odor whatsoever, even in the closed building. This alone is enough to solve the NIMBYs.

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#20
In reply to #4

Re: Waste water treatment

11/30/2008 6:41 AM

I am curious to know the cost of that system to install and operate. What is the physical footprint of this system?

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#21
In reply to #19

Re: Waste water treatment

11/30/2008 6:47 AM

Hello Yooper1946:

You just caught me as I was thinking about bed!

It may have been at my end, in fact it is probable. As it works this time.

Thank you, I will have a look when I get up. I will put a short-cut on my desktop. Thank you.

Have a nice weekend, or what's left of it. Last time I looked it was thursday, now Sunday.

Take care...............

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#22
In reply to #10

Re: Waste water treatment

11/30/2008 6:49 AM

Sorry to hear about the foul odor from the plant near you. That problem has been solved here in the US, link to www.mmfwater.com If you keep an open mind, you will see the future of wastewater treatment. Read my post from earlier this morning. I am not an engineer, and not a salesman. I am a citizen watching waste in local government. It will do no good to pick this system apart until you see it in operation, or talk to the people at Woodsville, New Hampshire who are operating it. Billions of taxpayers dollars are at stake and will be wasted on old technologies that will have to be replaced far sooner than they should have to be.

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#23
In reply to #22

Re: Waste water treatment

11/30/2008 7:54 AM

Hello Yooper1946:

I am sorry, I am getting so tired I am confued. Did you ask me a question about how large the local sewer works is? Or was that aimed at the OP?

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#24
In reply to #22

Re: Waste water treatment

11/30/2008 7:58 AM

Hello Yooper1946:

I have to go to bed, OK?

Will catch up with you later...........

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#25
In reply to #1

Re: Waste water treatment

11/30/2008 8:10 AM

Can you pl .clarify one matter for me about your post. at one point you state "Anaerobic systems are extremely slow: you'll need between 15 to 60 days of retention to effectively digest the wastes" Then you have given different anaerobic methods and state 2-10,4-12 etc hrs detention time. This confuses me Retention & detention! Can you pl. clarify?

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#26
In reply to #25

Re: Waste water treatment

11/30/2008 9:19 AM

Retention and detention time are the same thing. The reason for the apparent discrepancy is that for anerobic systems to completely breakdown and stabilize volatile organic matter, it will take anywhere between 15 - 60 days, but if you want to just reduce a heavy BOD loading quickly so that follow up aerobic treatment can be done cheaper, the different anerobic methods listed will deliver the approximate results given, depending upon reactor temperature. The higher the temeprature, the faster the breakdown.

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#27
In reply to #26

Re: Waste water treatment

11/30/2008 11:58 AM

Hi Everybody, thank you for all your comments. Special thanks to DVader1000 & babybear. I wish to give below facts once again. This is for a resort area and there is no central treatment facility. So no choice other than to go ahead. I am based in Sri Lanka and under the present economic scenario, decision to do the plant in house taking a risk is final & irreversible. So you can give me advice and also wish me luck! Our building consultant proposed a 100% anaerobic system and my opinion was different as explained below which led me to post this question. Anyway all these comments has lead me back to my original decision to do a up flow anaerobic process followed by an aerobic process (my thought is to go for an aerator based system) and finally tertiary system involving Chlorine dosing, Pressure sand filter, Granular activated carbon filter. My opinion is 80m3/day plant comprising anaerobic, aerobic & tertiary treatment. But I have never combined output from anaerobic as an input to aerobic and I was not sure how additional work it will involve aerobic bacteria to dominate in the 2nd stage. Now gentlemen I would welcome your opinion on what I plan. I estimate it will cost us about US$30-40,000 to implement what I plan. Please do remember I live in Sri Lanka and the cost here is probably 25% of that in US or Europe! My thanks again to the CR4 community for all the help & guidance.

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#28
In reply to #27

Re: Waste water treatment

11/30/2008 2:27 PM

You may want to consider ozone as the final biocide as opposed to chlorine. Long term, it should be cheaper, and no chemical residual to foul the stream. No dangerous chemicals to store & handle, either...I believe there are ozone generator manufacturers in India that you might find convenient.

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#29
In reply to #27

Re: Waste water treatment

11/30/2008 7:39 PM

One final word of advice. You CANNOT circulate from anerobic to aerobic and back again: the DO content of the aerobic system will kill the anerobic bacteria. What you should do rather, is to use the anerobic system to greatly reduce the BOD content and thus the loading on the aerobic system, and then use the aerobic system to finish the job. You can use a simple overflow process to transfer the wastewater from the anerobic bioreactor to the aerobic bioreactor.

Also, US$30,000 - $40,000 appears to be a little too conservative an estimate. I don't know what the inflation rate in Sri Lanka is like, or what the value of the currency may be relative to the US$, so try double or triple the amount.

On the plus side, you got the rest of it right. All the best to you.

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#30
In reply to #27

Re: Waste water treatment

11/30/2008 8:00 PM

Hello Sisira:

I want to offer my apologies for any rudeness from me, OK?

I think your decision to go with the upflow system etc, sounds good. As long as you can clean enough BOD to clear any danger of backup, it hardly matters how long the rest of the cleansing takes. As it is an integral unit, you will just be pumping over charcoal filter beds to do the rest of the cleaning, and as long as there is enough volume or space it is not critical.

Can I ask, is there any other similar dwellings and sewer works near you can check to see what quantities they are dealing with for roughly the same number of houses?

You know, it may be that these filter beds are available 'off the shelf'? Have you looked?

This gives an Estimate but I am not sure how up to date it is.

You could perhaps check your costings against this estimate of plant build cost, running, chemical, etc. break it down a little as I think this was for 50,000 people?

http://books.google.co.uk/books?id=G4tT0ESKVpUC&amp;amp;pg=PA10&lpg=PA10&dq=Expanded+bed+sewer&source=web&ots=bD9tialY-Z&sig=sEgDJUHMboz75KDFCdUDKTTFW8s&hl=en&sa=X&oi=book_result&resnum=1&ct=result#PPA13,M1

Check it out, they go into detail and may mention something you may not of thought of?

It sounds like to have done your costings pretty much but, of course you will also need to allow the cost of operating the plants.

Keep in touch

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#31
In reply to #29

Re: Waste water treatment

11/30/2008 8:11 PM

Hello DVader1000:

how are you?

That was good advice where you said you cannot reverse the process! I have asked him to look at the costings at the site I sent you yesterday. Because, I have no idea what the system and cost to all are over there, but I feel as you said the $30/40,000 is a great deal under what the true price will be. And there is the cost of running the plant afterwards?

Essentially, he is hoping to build this and run it (I assume) for the cost of an average car?......................I says NO WAY! Maybe $200/250,000 will be nearer the mark.

Take care.................

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#32
In reply to #31

Re: Waste water treatment

11/30/2008 10:42 PM

Hi Babybear,

I'm cool, how about you? You're right, an 80m3/day system is pretty big, and even a system that treats only half that will come close to US$100,000/- on average.

So, did you buy any radiometers?

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#33
In reply to #32

Re: Waste water treatment

11/30/2008 11:41 PM

Hello, DVader1000:

I am finding it hard as I am working by torch-light as the last Halogen Bulb lamp blew two nights ago. Each room has a different fitment..........oh for modern un-uniformity! Sashe-dashstibumliadle!!!!!!!!!

As to our future sewer designer, I guess he is between a rock and a hard place? He certainly has a lot of on-the-job learning to do. I am thinking as I looked for and gave advice from experience, that, we in the west are making savings on all kinds of things, And I am thinking efficiency here. Where, in a situation which is being designed as we speak, yet how much extra power per person is going to be used for this foolish money making scam? Nothing to do with our friend the OP. But the bankers, quick profit and run merchants! They are not going to be anywhere near the site in three years so who have they got to answer to? I think you could see my anger spilling out as I typed.

Right.............No is the quick reply. I have not god a radiometer yet. I know I have not been out much and want to perhaps go to London and I know of at least a couple of places to get one there. But, whether that will be before or after Xmas I am not sure.

I will send you a PM for further details if you don't mind.

Take care............

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#34
In reply to #27

Re: Waste water treatment

12/02/2008 1:16 AM

Hello Sisira,

I have search for "wastewater treatment in Sti Lanka", and picked a few sites which I though may help you, with regards to flow rates and general size etc.

The first site is goole search page 1.

http://www.google.co.uk/search?hl=en&rlz=1T4GGLJ_enGB294GB294&q=wastewater+treatment+in+sri+lanka&start=0&sa=N

========================================

These other sites are what may be useful. But when you, as a 'local' in Sri Lanka see sites on the google list you will have a lot more knowledge and ideas as to what they do and where they are, and how far away.

http://www.puritas.lk/

http://www.accessmylibrary.com/coms2/summary_0286-34782088_ITM

http://www-wds.worldbank.org/servlet/main?menuPK=64187510&pagePK=64193027&piPK=64187937&theSitePK=523679&entityID=000009265_3980630180734

http://www.uemgroup.com/clients-served.htm

This site has a big list of places, with flow rates, BODS etc, which you may be able to cross ref' or just check to see you are on the right course.

http://www.eco-web.com/register/04473.html

Puritas Ltd

Water and Wastewater Treatment, Sewage Treatment, Raw Water Treatment, Dendro Power Plants, Activated Carbon Face Masks; Waste Water Treatment - Domestic Wastewater: Septic Tanks, Ecological Sanitation, Gray Water Recycling, Phytoremediation, Constructed Wetlands & Reed Beds, Leaching Fields - Industrial Effluent Recycling: Zero Liquid-Discharge Systems, Closed-Loop Recirculation, Wet Oxidation, Solid-Liquid Separation, Oil & Grease Removal, Chemical Recovery, Ultrasonic Cleaning; Water Supply & Purification - Water Filtration: Filtration Processes, Filter Media & Cartridges, Microstrainers, Carbon Adsorption, Microporous Ceramic Elements, Backwashing; Air Pollution Control - Air Filtration: Fabric & HEPA Filters, Baghouses, Ceramic Filters, Cartridge Filters, Filter Media, Activated Carbon; Power Generation - Biomass Energy: Anaerobic Digestion & Fermentation, Gasification, Phytoextraction, Wood Chips / Pellets, Agricultural Residues, Biogas & Biofuel Production

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Telephone(+94) 11 - 268 39 63
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http://www.syskill.com.au/projects.html

http://www.idswater.com/water/australia/biocycle_wastewater_treatment_systems/solid_wastes/12999_0/directory_listing.html

Take care and come back if there is any problems, OK?

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#35

Re: Waste water treatment

12/02/2008 3:26 PM

I have been sick for the past two weeks and just got back into the swing of things. I would like to offer my 2¢ worth if I may.

I have personally built at least 75 sewage treatment plants that are being used to treat the waste from subdivisions, apartment complexes, mobile home communities and various other places where municipal sewage treatment was not available. The rules vary from area to area and probably from country to country as well. I will give you a scenario that works, without regard to the local regulations. The system can be modified to the extent required by the local government or regulatory agents.

The loading for 75 condominiums can be set at 350 GPD (Gallons Per Day) per unit. This would equal a total daily flow of 26,250 GPD. The BOD of 200 mg/L is adequate and an accepted value. That would be equal to about 43 pounds of BOD per day.

I would use a standard extended aeration system with a capacity of 30,000 GPD. This would be preceded by a flow equalization tank of 12,500 gallons capacity and having two grinder pumps and a blower with a capacity of 20 cfm @ 3.5 psi. The plant would be equipped with two blowers having a capacity of 120 cfm at a pressure of 4.5 psi. The plant would also have a 4,500 gallon sludge holding tank with diffused air for circulation and to keep the contents from turning septic.

The plant as described so far would be capable of reducing the BOD by about 85% to 90%. To accomplish further reduction, there would be a dosing tank with two submersible pumps, each rated at 117 GPM at 15' TDH pumping onto four sand filters (only one at a time) that are 25' x 25' each. The composition of the sand filters would be three courses of graded gravel 3" deep each, on the bottom of the filter, the largest at the bottom being 3/4" to 1-1/2" in size, the next being 1/4" to 1/2" in size and the top layer being 1/8" to 1/4" (#8 sand). On top of these three layers of gravel there would be 18" of silica sand of 1.0 mm with a uniformity coefficient of 3.0 or less.

The filtrate that comes through the filter would then be passed through an ultraviolet disinfection system with about 7 seconds retention and would have four bulbs and operate on 115 volt power. This would kill the remaning bacteria and the effluent would be suitable for discharge to most any surface waters (stream, lake, ocean, etc.)

A system as described would cost about $200,000 US. I know that's a far cry from the $40,000 US that you have projected. However, if, as you stated, the money is approximately 25% of the US dollars, then it may not be too far off.

This system would require two blowers with 5 HP motors, two grinder pumps with 2 HP motors, two dosing pumps with 1/2HP motors an ultraviolet system with four bulbs probably equal to two 100 watt light bulbs and a single blower with a 1 hp motor. If electricity costs about 8¢ per KWH (as in the US) the cost to operate the system in the US would be bout $450 US per month. The operator of the system would need to spend about 2 hours per week at the plant. The balance of the time the system would operate unattended.

DVader1000 is correct in that the aerated system is much more effective in this situation than the anaerobic system. By manipulating the operation of the system, one can achieve complete nitrification and complete or nearly complete de-nitirification. A lot depends on the manner in which the system is operated. There would be a production of waste sludge that would be required to be removed from the system about once per year. A local septic tank pumper could do that.

Someone alluded to the odor from the system. The only odor from this system would be a slight "musty" smell if you are right over the plant. This would be akin to the smell from a damp basement. It is not overwhelming nor offensive. If there is a foul odor present, the system is not operating as required. A well operated system will have no objectionable odors.

Didn't mean to get so "wordy" with this, but you have come upon a system about which I am familiar and I wanted to impart as much information to you as I can. Hope it helps. I know that more information elicits more questions. If you have any, don't hesitate to contact me through this site.

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#36
In reply to #29

Re: Waste water treatment

12/02/2008 5:24 PM

Something to consider.

Anaerobic is only really good for denitrification processes and methane generation. It is really slow compared to aerobic for removal of BOD, and requires more operational storage for treatment (slow processes require greater detention times). Aerobic would remove most of the BOD rapidly and require less treatement space. You typically want to run anaerobic process in the lead position to transform amino acids to NH4 and organics into methane, and try to strip it out. Aerobic processes will transform organics into carbon dioxide and aminos into nitrate. It is possible to post treat with a anaerobic process just to denitrify, but this requires a careful balance to control the DO.

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#37
In reply to #36

Re: Waste water treatment

12/02/2008 9:30 PM

Guest, GA for you. Please register since you clearly understand biotreatment processes well.

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#38
In reply to #36

Re: Waste water treatment

12/02/2008 10:44 PM

Hello Guest,

unless it is because you have not signed in, join now, you knows your stuff, GA

Take care...........AND JOIN!

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#39
In reply to #36

Re: Waste water treatment

12/02/2008 10:57 PM

Hello Guest,

I have not been there, but, judging by the other Wastewater treatment plants I have seen on the web in Sri Lanka, it seems there is not much room around most of them, so we here in the UK would perhaps collect the waste after cleaning, and also cow and pig manure and spread it on the Fields and leave it for a couple of years, that is not an option for this OP. (Original Poster).

The population is too dense and there is always possible run-off to deal with. Here we have no-one working in the fields and the nitrogenous stuff spread on the fields is great for production after it breaks down.

The Aerobic does work fast but is not somthing I would want in my backyard. I know there are ways to use the methane but, on a small scale what would you use ti for?

Doesn't half 'whiff' though after the spreading...........Phewwww!

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#40
In reply to #35

Re: Waste water treatment

12/03/2008 3:44 AM

Hello The Commoner:

I hope you are in full working order?

Yes it was me who mentioned the odour. The plant has had a lot of money spent on it and there is no smell now. But it completely depends on how the plant is run?

Why were you not here when this question popped in?

You certainly know your stuff, but I suppose you should have learned something in the building of 75 Plants?

Brilliant Sir! A GA to you.

Take care................

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#41
In reply to #21

Re: Waste water treatment

12/03/2008 7:43 AM

G'day to ya, just wondering if you had any luck linking to www.mmfwater.com ? This company has installed several test units within the Dallas, Texas, USA wastewater system with great results. Dallas is planning to buy this system to create a 140M/GPD system which will be built from scratch and operational in less than 9 months. Huge cost savings for installation and operation. The entire system can be overseen by laptop via the internet as well. Mimimal personell as well as NO PITS OR LAGOONS REQUIRED, thus virtually no odor to offend neighbors.

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#42
In reply to #41

Re: Waste water treatment

12/03/2008 10:02 PM

Hello Yooper1946:I have not had times today. I have been trying to help find info for a couple of people and time flies you know?

I will try it directly after I sent this. If I can get a shortcut I can view it whenever? How much space is that 140M/GPD system going to occupy?

It sounds the way to go in the future, and you say the test sites have good results.

I am going to make myself a coffee I think.

Take Care...........

See you tomorrow if nor earlier, oh, it is tomorrow........

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#43

Re: Waste water treatment

12/05/2008 1:36 PM

A buisness accociate of mine has come up (and applied for patent) with a treatment system, which is a bit out of the ordinary. It has been intoduced with much success in Roatan Handuras where the water table is to high for traditional septic applications. The system utalizes multiple perculating chambers filled with special bacteria/enzymes in stages to break down solid waste. When the waste is sufficiently broken down it moves through a controlled drain field filled with a special tropical plant that thrives on the nasty bi-products of the bacteria/enzyme solution. by the time the water reaches the end of the root-wad plant field it is 99% pure, and quite drinkable. Independant Lab tests conducted in the US verify the results. The unit is currently employed to treat the waste water of multiple locations including a newly built resort on the island. Thought it might be of interest

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#44
In reply to #42

Re: Waste water treatment

12/06/2008 8:11 AM

The total area required is about 20,000 Square Feet, or less than 200 Square Meters, if I did the conversion correctly. This includes a building that will accomadate the entire control center, maintaince office and employee break room. I am impressed by the ability to remotely monitor and control the entire system via the internet, using a laptop. In due time, it may be possible to control the system with a cell phone. It is truly the system of the future. 140M/Day will produce a daily energy equivalant of 16,000 Gallons of gasoline. Of course, it is mostly methane gas, but when compressed, it is a valuable fuel. There is a trend here in the USA toward converting gasoline and diesel powered engines to Compressed gas. CNG is much cleaner burning so engines last longer and of course, the atmospheric emmissions are minimal. Come back with your input.

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#45
In reply to #43

Re: Waste water treatment

12/06/2008 8:18 AM

I would like very much to learn your associate's name and if there is a website that has information on it. I would like very much to contact him. Thank you

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#46
In reply to #44

Re: Waste water treatment

12/06/2008 9:02 AM

Hello Yooper1946:

I have seen the site but not in detail. I have been so busy doing searches for people.

It is not very big for the quantity >>>140Metres/day<<< Is this correct?

Just to run over this so we are in the same 'ball park'...............

20,000 / 9 = 2222² Yards. /1.196 > M² = 1858.

It does sound like the way to go for sure. But 140m³ a day is still pretty small. You mentioned in another post it would be taking the waste from several large cities? Is that right? Where does the 140m³ come from?

Thanks for the post by the way.

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#47
In reply to #46

Re: Waste water treatment

12/07/2008 8:45 AM

The space required by the Clean Stream system to process 140 million gallons per day of sewage is only 20.000 square feet. Converting the area to square meters, the space required is less than 2,000 square meters. Because the biosolids are removed before any chemical treatment, there is no need for any digesters, eliminating the requirement for ponds or lagoons of any type. Huge space savings and thus costs are the result.

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#48
In reply to #9

Re: Waste water treatment

07/18/2009 10:26 AM

Hi Sisira,

On the BOD:
The BOD you've mentioned (200) is too low according to my experiens.

I would say that values greater than 400 are more realistic. But this is according to local values.

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