Filtering Suspended particles from water

[echnidna]

I have thought of doing that. All you need is an old window, a bath tub, a bit of gutter and a pump. Will definately mess about with something along those lines one of these days. Will I be game to drink it? Hell yes!!

I have also been experimenting with distilling. I took a funnel and a bit of rubber hose on a coastal walk I did last year. The funnel goes over a billy full of seawater and the hose comes off the top and you coil it up inside a big mound of wet sand. The idea is that the sand absorbs the heat causing the steam to condense. It works OK but takes a lot of seawater and a lot of boiling to get a cup full because it's not very efficient. What comes out is pure water though. Next trip I'm going to try something enclosed with a lip around the inside of the funnel. You fill the top with cold water to help the steam condense and it runs down the sides of the funnel into the lip. You have a little spout out the side where the water runs out.

The filter would have a much faster turnaround. With a still, I would need enough storage capacity to keep the loos flushing while water is being distilled, which could take days to do a few litres at this time of the year.

I'm extremely rusty on the figures but from memory 1 sq metre of water will evaporate about 2 litres of water per hour in mid may in Melbourne.
So as long as you have a large enough surface area (say on top of the roof of your shed) you can get quite a good amount of evaporated water.
On sunny days there will be far higher evaporation.

A Council Helath Inspector should be able to tell you the evaporation rates applicable to your region.

[wilco]

Swimming pools generally use a medium or high rate sand filter, these require pressure so may not suit your application.

An older style of filter still used on some pool today is a 'gravity sand filter' ive attached a pic for you to see how it works. this would not need very much pressure, just enough to get the water to flow over the 'wier wall' gravity does the rest, a benefit of this system would be sunlight hitting your water, UV light kills nasties so would be a bonus in this application, this could be built on a small or large scale... i can explain further if you need.

Thanks,
Luke

[Clinton1]

Oh, and the hydroponics setups I've seen use a clear pipe segment that has a UV light shining through it to sterilise the water.

Have a look at Tenix's website, they bought the intellectual property rights to Environmental Solutions International (share market listed then went bust). ESI used filtering and bacterial digestion techniques to treat water, and pioneered the use of sewage and bacteria to make bio-fuel. Perhaps Tenix have some info available on a web page.

I'm thinking that you might set up a gravity sand filter system (44 gallon drums is series) and charge the system with the bacteria mix that your local sewage treatment works uses. You'd need to add air to the mix to boost the bacteria (solar powered fish tank aerator). Then filter this and use a flocculant. I think it would be a fascinating project.

Or, set up a reed bed (a trench lined with a dam liner) and take water from the 'treated end'.

[Driver]

It's a problem to solve, that's all. Gives me something to think about when I stand and/or lean.

I urge you to caution, Brother Silent. If, in the course of thinking about this problem while standing and/or leaning, you should come up with a solution then the possibility exists that you will have completed a Work In Progress (WIP).

I would hate for a stalwart like yourself to inadvertently breach the Code. :eek:

Col the Cautionary.

[Sir Stinkalot]

Ok here are my views .....

Firstly I will qualify this with saying that I obtained a bach. Engineering (environmental) only a few years ago ..... this basically focuses on water treatment. Secondly ..... following graduation I have never used the information that I obtained and most of it is now gone. Luckily I kept some of my big books ...
"Wastewater Engineering - Treatment Disposal Reuse" Metacalf and Eddy
"Introduction to Environmental Engineering" Davis and Cornwell.

Ok now lets get into the problem ....

Substances that can exist in water fall into one of three classifications:
Suspended
Colloidal
or Dissolved.

A dissolved substance is one which is truly in solution, and is homogeneously dispersed in the liquid. The substance cannot be removed from the liquid without accomplishing a phase change such as distillation, precipitation, adsorption or extraction.

Suspended solids are large enough to settle out of solution or be removed by filtration. In this case there are two phases present, the liquid water phase and the suspended particle solid phase.

Colloidal particles are in the size range between dissolved substances and suspended particles. They are in a solid state and can be removed from the liquid by physical means such as very high-force centrifugation or filtration through membranes with very small pore spaces. Colloidal particles exhibit the Tyndall effect, when light passes through a liquid containing colloidal particles, the light is reflected by the particles. The degree to which a colloidal suspension reflects light is measured by turbidity.

Colour is not separate from the above three categories, but rather a combination of dissolved and colloidal materials. It is very difficult to distinguish "dissolved colour" from "colloidal colour". The most common cause of colour is the occurrence of complex organic compounds that originate from the decomposition of organic matter.

The particles in the colloidal range are too small to settle in a reasonable time period, and too small to be trapped in the pores of a filter. As this is the case a coagulant must be added in order for the colloidal particals to produce a flc. The coagulant is often alum.

To cut this short as the Stinkette wants the lapton :mad:
The floc makes the colloids of a size where the can settle, hopefully removing the colour problem.

The problem in silentC's situation is that the coagulant will need to be added often, mixed with the water, then given time to settle, prior to being used. This will be a labour intensive process and require a number of holding tanks. The other issue is if the water isn't fully treated and stored it will become septic again which will be worse than the colour problem.

Ahh hope this helps ..... got to go.

[silentC]

OK, all good stuff one and all. I will ponder it some more. Don't worry Col, there's no immmediate danger of WIP completion, plenty of other things on the boil that are more important than the colour of the water in the loo!

Might give the gravity sand filter a go as suggested by Luke. Easy to make and nothing to lose by trying it. I need to absorb some of that technical stuff a bit more. It might be worth getting it tested to see what's actually in it but that's dangerously close to doing a proper job of it!

The reed bed was one of my earlier ideas. I saw one on TV a couple of years ago and I liked the idea. Good thing we have plenty of un-landscaped land to play with.

Thanks for the input.

[silentC]

Luke,

In your diagram you show "collectors". I gather the purpose but what are they actually? Some sort of perforated pipe or...?

[wilco]

I believe a perforated PVC pipe would work fine, put a fine screen across it, flyscreen etc with aggregate surrounding it, then the sand on top.

Pool shops ,or i can give you a supplier, will sell you filter sand, you can get different 'grades' or sizes to suit the fine screen you have installed.

Does that make sense?

You'll also need a way to baskwash this, it could be as simple as a connector for a garden hose and tap water, you need enough pressure to expand your sand bed and carry away the crap but not enough to wash away your sand.

Its also good to note with these types of filters that generally the water is not totally filtered with one pass through the system, roughly speaking
1 pass will remove ~65% of the solids
2 passes 85%
3 passes 95%
4 passes 98% etc

Luke

[wilco]

Actually, with backwashing etc, a multiport valve, like on home pools and spas would make things easy for you to control backwashes once you have sorted out the pressures youll be using

[silentC]

When I was thinking of using a pool filter, my idea was that I would just circulate the water in the holding tank periodically. So the water would flow from the tank, through the pump, through the filter and back into the tank. For back wash, I would take water from the tank the other way through the filter and send it to the septic. That way the crap would go into the septic and we recycle the backwashed water as well. I don't know whether this would result in some sort of build up over time with the fine crap that normally goes on the garden ending up back in the tank.

I thought I would try some beach sand first. Got plenty of that nearby A bit of aggregate in the bottom, maybe even some charcoal?

I'll see my mate at the pool shop and see if he can source me an old valve, or maybe even an old filter and pump.

[wilco]

When I was thinking of using a pool filter, my idea was that I would just circulate the water in the holding tank periodically. So the water would flow from the tank, through the pump, through the filter and back into the tank. For back wash, I would take water from the tank the other way through the filter and send it to the septic.

Perfect!

You could try this on a tiny scale with 2 buckets to see how it will work. Poke a hole the in bottom of bucket 1, cover with mesh, fill with a little aggregate then sand.

Place bucket 2 below bucket 1. Pour sample water into B1 and collect in B2. Circulate same water a couple of times and see if you get an improvement. Total cost should be 2 buckets Apples!

[wilco]

That way the crap would go into the septic and we recycle the backwashed water as well. I don't know whether this would result in some sort of build up over time with the fine crap that normally goes on the garden ending up back in the tank.

One of our backwash tanks (it holds the backwash water while it is being pumped into the sewers at a slow rate) is connected to 3 high rate sand filters at work. It takes all the backwash water from our 1.2million litre lap pool. After 7 years there is still only a small layer of sediment at the bottom. it should not be a problem

[jimc]

New Inventors on ABC has had a retrofitting treatment system to fit to existing septic tanks that use worms and other creepy crawlies to turn your sewage into clear water.

another alternative is do what nature does...build a marsh/swamp in an enclosed system...ie pond liner. As the dirty water drains into the system it will be cleaned and then pump it to whereever use you desire.

Add a UV lamp and you could drink it!...although I probably wouldn't.

There has been a lot of research into this process. Check out http://www.sustainablehouse.com.au/ They have a similar treatment system I have described.

[silentC]

Good idea. I've got plenty of buckets!

[silentC]

New Inventors on ABC has had a retrofitting treatment system

Saw that last night. Biolytix. Have already contacted them. The water that comes out of it is still tainted though, so I would have the same problem I have now. The advantage of that system is that it requires no pumps, or can be run on solar, and it uses no chemicals. The system I have now has a water pump for distribution and an air pump to help the bacteria do their job. It runs the treated effluent through chlorine on the way out and the tablets need to be replaced peridoically. The water is OK for above ground irrigation but as mentioned above it is brown.