Specifying Water Treatment for Release into Mains Drainage

You might want to consider the footprint. Settling tanks, clarifier's, or membrane filters are going to take up a lot of real estate.

Sorry I couldn't help more. Good luck!

Thanks kilowatt - I think that will frighten the bosses (if not the horses!).

About discharge standards : The UK should have some.

Even SA will eventually have a standard.

You could also contact the World Health Organization for a more global approach.

I seem to remember that the US raised their standards recently - You may have to be prepared to design at higher than regulated standards.

About disposing

There was a study done in SA under the Water Research Commission (2005) and it proposed a lot of measures to dispose of abundant supply of sewage sludge including for example mixing it with clay to produce bricks. But you need to analyse the composition and determine some solutions.

Hi Rose,

Yes, wastewater treatment is required for your plant. Aside from the data you can furnish, please also furnish expected discharge effluent quality. I design such systems for a living, and if you can furnish the data I requested for, I can design a system for you so that you can get a better estimated quote from your would-be vendors.

"One report we have says that the high sulphate and silicon content of the water may inhibit further use"

Precipitate them out with lime. The good thing about this process is that you can recover valuable calcium sulphate (gypsum) and calcium silicate that you can sell off to defray the cost of the treatment process. You can reuse the water after this.

What can you do with your sludge? That depends on its exact composition. If there's nothing toxic in it, it can be subjected to anerobic decomposition or composting. If it contains toxic substances such as heavy metals, you'll need to get a toxic waste disposal specialist to remove it. Let them worry about what to do with it if this is the case.

Feel free to contact me if you have further questions.

Hi Darth,

How's the asthma?

please also furnish expected discharge effluent quality

That's one of the things I'm trying to find out. The Water Authority that deals with the test plant waste is happy if we take out the solids and skim off the oil. Bar phoning each individual Authority (don't fancy doing that across Europe), I don't know where to look for legislative minimum standards.

Precipitate them out with lime

Thanks - I wondered if you could be "that simple" . I think the issue we'll have with selling off by-products is the low quantity, but it's good to know there's a market if quantities increase.

Sludge

Type 1

• Mostly inorganic carbon, with some organic carbon ( in the form of HC), other trace elements.
• 4.8 < pH < 5.4

Type 2

• 60% Iron Oxide
• 20% Carbon & Sulphur (LOI)
• 17% Calcium Oxide / Phosporus Pentoxide / Zinc Oxide
• Trace elements

The two will be mixed, Type 1 predominating. Specialist disposal is looking favourite - especially in the quantities (50 - 200 tonnes/year total) we're estimating.

It would be good PR if we could show that the waste is going somewhere useful (gypsum, road tar, power generation etc) as the DPFs are pollution control devices...

Thanks again, I'll be back (_{^{sorry wrong film...}})

Hey, I like the Terminator movies myself. Actually, I'm not asthmatic; the reason why I wheeze is because I breathe through an air pump.

Okay, your basic process should go something like this.

Influent → sedimentation → oil skimmer → lime precipitation → coagulation → flocculation → clarification → pH balancing → effluent reuse. The accumulated sludge in the clarifier should be pumped into a sludge thickener before being pumped into a filter-press prior to final disposal. A word of warning: oil and lime don't mix. You'll get a really horrible sticky mess if they do.

Going by the contents of your sludge, it would be best to let a toxic waste specialist deal with it. They'll probably sell off the sludge for roadworks or construction or something similar.

Glad to be of help. I guess my mom was right when she told Qui-Gon that few things make me happier than being helpful.

Thanks Darth, that's really helpful. The tip about oil and lime is noted !

You know, not everything Obi-Wan said about you was true

We also end up with water waste with particles in, mostly phosphor but, because it is used in very small quantities the outfall is also small. The local water authority insist that we settle out the solids which we do with a settling tank. This tank is just a domestic cold water tank baffled into a series of compartments. The quantity we produce is so small that, after several years of using this system, we have not yet had to deal with disposing of the solid waste. We are aware however that the local water people regularly take samples from the drains to ensure that we comply.

Thanks Nigh. One of the things we have been told is:

"Water Authorities make their money treating water...so let them do it and just pay the disposal premium."

I want to keep with this, we just need to understand what the minimum is we have to do and how to do it economically to the quantities we're dealing with / expecting to dealing with in different locations.

English Rose,

Water from your cleaning plant need to be taken and all possible parameters and characteristics need to be analyzed and then comes the apt treatment process setting, the cost of which is bothering your end it seems.

I have an alternate suggestion- if your cleaning fluid can be replaced by a non pollution prone fluid, will it be acceptable to you?

If your answer is yes, Now I would recommend you to go for the air based cleaning process since Air does an excellent cleaning job and escaps away with out any suspended or dissolved pollutants. Think and try out this option to solve your water treatment problems.

I have no idea about diesel particulate filter, which may have to be borne about.

Thanks for your comments - unfortunately air cleaning will not work in this case, it has been tried. Diesel soot is quite "sticky" and air is not able to remove enough of it from the substrate pores.

Water does a very good job of cleaning the filters - it's finding appropriate cleaning methods for the used water that is needed. This is outside my field(s) of expertise, hence asking for help.

The water does NOT need to be potable at the end, just suitable for mains drainage disposal or re-using in the cleaner.

Thanks again, I'll post updates.

Great question but very open ended. I would check with the local utility for sewer use bylaws that may provide you with targets for treatment. The BOD and COD levels will be specified in any use bylaw. With regard to volatile compounds, most do not have any tolerance. The utility will worry about gas build-up in manholes and mains. Related safety is a serious factor. I am not sure of the type of treatment that will be required but air stripping could be a consideration. The volumes of treatment are low and hydrogen peroxide/activated carbon could be a good polish after removing the big gunk. Sorry I cannot be more specific.

Cheers and good luck

hi Kevin, thanks for the tips. I was hoping someone could point me to a central source for by-laws, but it seems that was hoping for too much. I should have known: the UK Statutory Instrument amendments are not kept together...it's a miracle anyone knows what the law actually says....

If we can reuse the water, with losses being in wet filters that air dry by evaporation; wet sludge and general evaporation, we may be able to avoid the drains entirely, which would simplify things in one way by avoiding local bylaws. We'll be able to assess that once we have quotes and understand the complexity of the treatment plant.

Check out the discharge consents already in place at each facility where it is intended to operate this process, as consents vary from location to location within the same Water Authority's district. Local offices can advise as appropriate. If the additional load on existing facilities were not to send it out of consent, then no additional treatment is necessary.

If the added materials sends the combined effluent outside the pH limits, then add either acid or alkali to bring it inside as appropriate, ensuring that the pH instrumentation is linkable to an appropriate calibration standard at appropriate intervals. Some tankage might be necessary to achieve this.

Consider blending the new stream with other existing streams, as the combined stream may require less treatment than the original, with savings to both facilities. This technique is already done with a factory and a hospital in South Essex.

It depends upon what is present in the "chemicals" as to whether or not any additional treatment is required in each case. Of particular concern are turbidity, heavy metals and oils, and these parameters will be stated in the discharge consents.

Maybe it is time to open a dialogue with a specialised treatment company?

It is way too soon to provide "a budgetary figure for a treatment plant".

Thanks PW.

Maybe it is time to open a dialogue with a specialised treatment company?

I wanted to understand more (something) about what was required before we did that ... currently working on the RFQ to send out.

It is way too soon to provide "a budgetary figure for a treatment plant".

I was after understanding what I needed to tell the specialist company so that they would be in a position to give us that - we're now thinking that "total" recirculation is the way to go.