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Sand Filters - Requirements for Continuous Flow?

maramc

Members
After Doug's talk on his fish room set-up, I continued to educate myself (Google search) some of the concepts that he has in use. One of the those was the sand filtration of his water. I then realized that a vacation home in FLA that I have the opportunity to stay in has a sand filtration system in place for the water supply to the home. Didn't know much about it before except my mom touted it as a great and efficient way to filter the well water. I've seen it, but can't provide any specs. on it.

Anyway I have a question about sand filtering that I haven't found an answer for on the net. Does the sand filter have to have "continuous flow" to work? What happens when the water isn't running the house for a few months? Does the BB still do it's job or does it die?

CCA has been been great for explaining all kinds of concepts and I am amazed how many relate to stuff that affect other aspects of living beyond the aquarium!




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chriscoli

Administrator
Although this is not my area of expertise, I'd think that a sand filter for a house is serving a different function than one for an aquarium. I think back to my days growing up in Phoenix....one of my chores was helping maintain the swimming pool. There the sand filter was meant to trap small particulates, not to alter the chemistry of the water. If it's just a filter thats providing mechanical filtration, then I'd imagine it can sit idle.....maybe being flushed for a bit when restarting, but that shouldn't change it's function.

Biological filtration on the other hand, would not benefit from sitting idle.
 

Localzoo

Board of Directors
I think there are many variables to it and since I've just now started to learn about the sand filters i would not know where to start.
Temp of water
Has the filter been cleaned
Is there enough "food" for the bb to munch on while off
etc etc

Hope someone comes along soon that has some really good expertise to help you out.




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There are different kinds of sand filters that do different things. My first filter for the room as a VERY large sand fluidized bed filter. It housed 75 pounds of sand and had maybe 10 gpm flow going from the bottom to the top of the filter. This fluidized the sand into a milk shake consistency. They do the nitrification process ONLY, regardless of what people say, so they can be the traditional bio-filter.

You can youtube sand fluidized bed filters or just click this:
http://www.youtube.com/watch?v=xutRnqYtPdw

Again, mine is 5 feet tall and like I said has 75 pounds of sand.

The issue I had with mine 2 fold. I was running out of flow on my 1.5hp water pump and needed to build out my last section and the other is everytime the electric went out, the bacteria in the filter died.

Now there is also something called a bio-sand filter that flows from the top through the bottom and has both an aerobic and an anoxic (no oxygen) zone. This is the filter I discussed during the meeting. I spent weeks researching for my design starting with those used for the homes but quickly just went waste water treatment thesis' for design. The one I just is based on some used in Bangladesh which has to remove iron but more importantly arsenic which poisons 30+ million a year and 60% of the population has unsafe water.

Here is a youtube of something close to mine :
http://www.youtube.com/watch?v=2KQNzhK9-mA



Both filters need a constant flow, the first to keep it suspended in water, the second to keep oxygen (dissolved oxygen or oxygen in the form of nitrites/nitrates no2 and no3). If flow is not being kept constant, a die off will happen.

My guess is the filter in Florida is something akin to the bio-sand filter I use for denitrification.

I hope this answers your question. I could go on for days on this stuff, even went so far as going for a visit back to UVa to see about finishing my engineering degree in environmental. In the end, a VERY astute dual PhD student working on her third Engineering PhD (who said professional students were slackers) told me I would be better off working for someone thesis than wasting my time in Engineering Statics or MatSci
 
On another note, glad my talk did not bore everyone. I was afraid I would hear people's heads hit the tables when I got to here.
 
As usual, start preaching and forgetting the questions raised

Does the sand filter have to have "continuous flow" to work?
Depends, for turbidity (cloudness... mechanical filtration) no but would think that if used for a while, the bacteria will die off leaving water with ammonia in it. Not sure, but would think so.


What happens when the water isn't running the house for a few months? Does the BB still do it's job or does it die?
Has no choice but to die.
 
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maramc

Members
Doug - Thanks for taking the time to explain! I find many of the topics discussed on the forum satisfy my inner nerd ( that's a good thing IMO). Filtration concepts are pretty cool.

The house Is located on a spring fed lake. The house water has a eggy smell initially, but it goes away after flowing some water. The egg smell comes back if you use too much water in a short period of time. However being raised on well water, the smell isn't is bad as some of the systems I've had the opportunity to enjoy. Next time I'm down, I'm going to see exactly what it is and may try to figure if it's necessary to have something done to make it safe/effective.


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eggy smell maybe sulfides, its what I get when "tuning" my denitrator and using too much vodka. Going to start trying white vinegar on one of them tonight instead of vodka, I stumbled across a waste water plant using acetic acid and thought this might work
 
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