Removal of Chloride from Water

usually before you run an RO system the water has to go through a primary treatment process, RO is generally considered to be an expensive secondary treatment. the idea is to keep the chlorine out of the water as best as possible to begin with, but they do still have to disinfect their effluent prior to discharge, chlorine is still the most cost effective way to achieve that. no matter how you add it up it always comes down to money, changing the standards will not fix anything, nor will piping it into the ground, it wont magically disappear. after enough time a plume will move through the underlying ground formations and pop up somewhere else! so either live with current standards, tell the farmers to get a different source of water, or open the checkbook and screw the taxpayers to appease a special interest group with an influential lobby

The RO waste water gets pumped into the ground and since our water supply is from our local lake and underground sources upstream from the dumping site, we shouldn't have to worry about the underground chloride making it's way to our water supply. Also, the water from our sewage system flows to a river, which ultimately makes it's way to the ocean. Along the way, farmers pull water for farming.

Thanks for the advice.

Option 5 was discussed early, however the problem arises from too much water being used for "outdoor" vs "indoor" - gardening, sprinklers, etc. The amount of incoming water that needs to be filtered will be too high and the cost excessive.

Option 6 is what the Dept of Sanitation wants to do. Small business owners will get hit with an excessive fee to 1. Connect to the system and 2. Annual fee. For instance, to open a laundry facility, the business owner can expect to pay over $100K in connection fees, plus $10K/year in annual fees. Car washes, restaurants and other water intensive businesses will be hurt tremendously by this fee, which of course will simply be passed to their customers.

This is why we're looking for an alternative.

I don't think the cost would be passed on, I think it just kills off more business and jobs to sustain a small group of farmers growing crops in an arid environment. you're near a breaking point where the numbers just don't add up anymore. the tech is there to reduce the levels to a more desirable level but the total costs involve mean your farmers are passing the buck and someone other then themselves in order for the farmers to sustain their self- entitled profit margins let them move to Arizona and tap into the water from the Colorado river that was taken from Socal years ago for agriculture. the farmers problems are their own, NOT the taxpayers. if their business model no longer works in California tell them U- Haul still heads East On THE 10

Fredski, Amen!

Also, the farmers have stayed in business with the so called "high chloride" water for over 40 years. If the water were that bad, the crops would've died and they would've had to close up.

Good idea, however this was also discussed and not feasible, due to 1. The cost of fresh water - we forget that LA is a desert. and 2. The county and state will not allow us to "waste" our precious fresh water.

option 4....tell the farmers to pound sand or pay for the purification themselves

Brave Sir Robin: Excellent. I think, there is some advantage in paying the farmers directly and asking them to have local processing of removal for which polluter pays. They get infection free water and only have to remove excess chlorine.

This part is to the Original Poster:

I think, it is not just Chlorine alone and there may be some acid, toxic salt or something else which may be most heinous in the water along with Chlorine. In that case it may be a very serious matter. If you remember that Lithium Chloride pollution then it is not just Chlorine but toxic Lithium that also goes with it.

UV is not at all a solution.

Do you have a test report of what in all this contains?

Shyam, We're in Southern California = we have enough worries about pollutants and following the state regulations. Currently, they aren't asking for anything other than keeping the chloride under 100 mG/L.

The problem is that the state has set the level at 100 mG/L. Since this is the level we must adhere to, our city will be fined if we don't comply. Or we can try to get the state to defend the 100 mG/L level. For instance, another town (the last one I lived in) which is less than 15 miles away (straight line) is allowed 150 mG/L chloride. Why are they allowed a higher amount than us? Nobody has given us a good answer.

Mix incoming water with outgoing water to achieve a chloride level below 100mG/L.

This should cost almost nothing.

WJMFire, If we had an abundance of fresh water, this would be easy, but we have laws regarding the use/waste of fresh water. Good idea, but it won't work in our area.

120 mg/L of chloride does not seem excessive, for irrigation this should be ok for anything but the most sensitive plants....I would get some feedback from the farmers complaining, check the ph of the water and for any other ingredients that may be posing a problem, it might just be a problem that can be resolved by other methods....If it's just a few farmers that are complaining because the crops there are growing are unusually sensitive to chloride, then a smaller more focused fix might be viable....

http://www.ext.colostate.edu/pubs/crops/00506.html

http://www.gewater.com/handbook/ext_treatment/ch_8_ionexchange.jsp

http://www.gov.ns.ca/nse/water/docs/droponwaterFAQ_Chloride.pdf

Hi SolarEagle,

The farmers are trying to get chloride levels as low as they can, even though it may not be necessary. The state put the 100 mg/L requirement on us - it has been set at this level for decades and nobody can tell us why? It was some arbitrary number the state chose. Our neighbor over the next ridge has a 150 mg/L level and ditto for the town next door to them. Their waste water is used for irrigation of crops, however they are allowed a higher limit.

This is the frustrating thing we're dealing with. The state chose these levels, yet they can't defend them. So they threaten us with fines if we don't comply. We've been told they can run in the $M of year range, so the Dept of Sanitation was tasked to come up with a solution.

Perhaps some lobbying effort can be made on your behalf....Do you network with any groups? You need someone to find out who has the pull here and get in bed....politics is a specialty best left to those lawyer salesmen types.....if you know what I mean....

I suspect the level was set not so much on concentration but on the total amount of chloride that can be introduced in the farming area based on average daily flows. Based on 75.6 million L/day (20M gallon/day), a level of 100 mg/L means not more than 7560 kg/day can be introduced into the farm area. I do not know the total acreage that is to be considered under the influence. However, there are some crops like soybean that seem to need more chloride and is often introduced as a micro-nutrient. Not being a farmer or a person of agricultural expertise I can only surmise there may exist better crops to grow that will uptake any excess chloride. Perhaps a few farmers could be encouraged to grow these chloride loving crops to ease the need for excess sewage treatment. Just musing on alternatives.

Use ozone for disinfection of the waste water

You may want to look into injecting ascorbic acid, (Vitamin C).

http://www.fs.fed.us/t-d/pubs/htmlpubs/htm05712835/page12.php

Thanks for the info, but we need to get our chloride (ion) levels down, not chlorine.

Sorry, my metric is bad. mg/L is correct. Yes, we know about the 250 mg/L chloride level for drinking water and we've used this to back our claim that the 100 mg/L is too stringent.

So far, the state has not been able to substantiate the 100 mg/L level. What they have done is to threaten us with fines for not complying. This of course got the county up in arms and they tasked the Dept of Sanitation to come up with a solution. They presented our community with the four options in my post.

The farmers claim that their crops are being damaged from the excessive chloride, however they have been receiving water with much high chloride levels and they had no complaints. I know our chloride levels were much higher, because we had around 8,000 water softeners installed in homes - a program to rid the community of water softeners occurred a few years ago and it is considered unlawful to operate a water softener in a home that is connected to the sewer system.

California is the land of fruits and nuts.

And the grow some too

Thanks Autobroker and no problem. I went through the metric conversion about 50 years ago and found it made life easier in the water industry. However it, took time to adjust my behaviour from the old British empirical system.

First, I tried to find California standards that indicated 100 mg/L of chloride was indeed a standard. No luck on my side but perhaps I only did superficial drilling of the internet. You and the town should indeed press the state for the standard in writing.

Second, if the true or major level of increase in chloride is attributed to the wide use of domestic softeners discharging to the sewers, perhaps a sewer use by-law could be imposed to restrict discharges to the sewers. That would mean that home owners may be faced with some storage and trucking of their own backwash water to suitable locations. A little unpopular no doubt but a whole lot cheaper to put the cost on the culprits responsible and not everyone. Softened water used will not have any increase in chloride content. It will have increased sodium or potassium content.

If the incoming water is too hard, many or the majority of users will appreciate softened water. Lime softening may be a viable option and could be applied to the whole water supply. Lime softening adds neither chloride nor sodium to the water. It relies on the raising of the pH and precipitating calcium and magnesium (the hardness ions) from the water. Water is returned to the municipal supply with some adjustment to pH. It is less costly to install and operate than R/O water. However, that is an approach that should be weighed against all options by engineers that are familiar with all processes. Good luck.

Sorry, I just read your post where domestic softeners were outlawed, so I guess there is no need for a second sewer use by-law. Perhaps there is not full compliance with the ban and it is likely full compliance will not be honoured. If the water is hard and people do not like hard water the lime softening will usurp those who still use softeners under the radar. A survey of softener use may help if residents are cooperative.

Kevin, The California standard varies with each area. We're in the Santa Clara River area and our maximum chloride level is 100 mg/L. In Simi Valley, the limit is 150 mg/L.

In an attempt to reduce the chloride levels, a water softener removal program was implemented in the entire valley and they outlawed the use of salt based water softeners. I am not sure if you can have a Culligan tank exchange system, but I know that any system that you add salt to is illegal. When this was imposed, it brought the chloride level down, but not enough to pass the state requirement.

Our water isn't that hard, relative to other areas of So Cal. We get some calcium deposits, but nothing terrible. I don't think water softeners are necessary here - they're nice to have, but we don't need them.

Thanks for your input.

CR4 Admin: Spam: This post was modified because it contained advertising outside the Commercial Space forum. Please review Section 14 of the CR4 Site FAQ about advertising.

It makes sense to RO treat your input water to remove chlorides in it, as after usage you may add other chemicals which may damage expensive RO systems. You will find it cheaper to treat incoming water.

I am sure paying off farmers is proposed by some members as a joke.

(a) It will not solve the problem, It may come back to haunt you on a later day

(b) Chlorides even at some low levels are not very conducive to growth of certain plants though some (like coconuts) will thrive in a chloride environment.

Baloney! Here in the United States (especially in the western states) where ground and surface waters both contain chlorides way higher than what the OP mentioned, all crops thrive. Pure and simple baloney, Mr. Sisira.

Hi Sisira, We looked into removing the chloride from incoming water, however due to the amount of water being used for "outside" the home, it would not be feasible. I believe they estimated that 1/3 of the water is used indoors and 2/3 is used outdoors. We would be using 2/3 of our RO water for outdoor use and only 1/3 for indoor use - the water that makes its way to the sewage plant.

I also assumed that they were joking about paying off the farmers. That's a ticking time bomb.

I'm using activated carbon filter to get the chlorine out of the tap water.

Of course you'll need some huge filters .

Chlorine in water and Chlorides in water are two distinctly different things.

You cannot use Activated Carbon to remove Chlorides though Chlorine is removed by Carbon in a catalytic reaction.

I am a manufacturer of Activated Carbon in Sri Lanka and we sell a lot for de-chlorination of water.

I don't think you can remove chloride with carbon filtering, but I could be wrong. Chloride is the negative ion, where chlorine is a molecule.

Two other people have already commented on these treatments but have not put them together:

Incoming water add UV bank & O3 to remove all active bio and this will also SIGNIFICANTLY reduce the amount of chemicals needed to maintain potable standards.

Treated water again run through another UV bank & O3 this will disinfect the water back to potable standards and can be recycled if needed during drought conditions.

I have to point out that your conclusion is wrong, Question was how he could treat waste water to achieve applicable standards for waste water disposal and not to the level of potable water standards!

Anyway even if it is for potable water standards without knowing the exact composition of water no design engineer can come to the conclusion to use UV-c or Ozone or both.

Use silver nitrate and precipitate the chloride? This will kill all bacteria as well.

I think it would be very expensive to treat 20M gallons/day (to remove 20 mg/L of chloride).

Also, we're now adding nitrates to the water. If this reaches the ocean (which some will), won't the nitrates mess up the beach ecology? Isn't it similar to too much fertilizer being dumped into the ocean?

Andrew, thanks for your advice. Our community needs to reduce the chloride level in the treated water to below 100 mg/L. The problem is that our incoming water has chloride and through usage, we add more chloride, so when it arrives at the waste plant, there is too much chloride. The options to remove the chloride is given above, with solutions on how to get rid of the RO waste products. This is very expensive and I was hoping to find another option for the Dept of Sanitation ... or our community will have to go to battle with the state. Something that we're not looking forward to.

I don't know what state you live in, but that is a ridiculously low level for chloride (as in sodium chloride table salt). Road salt in many areas (that have winter) would raise runoff way above this level. Based on your statement: "Use UV light for disinfection" makes me believe you actually meant to be referring to chlorine. If so, the source water has a dangerously toxic level of chlorine in it (or your data is incorrect). If indeed we are discussing chlorine and not chloride, there is a rather simple way to solve the issue (20,000 gallons/day by your statement): (1) pass all the incoming water through activated carbon beds (filter vessels loaded with AC). Carbon reacts with chlorine immediately, and you do not have to meter chemicals, but you will eventually need to change out the carbon. (2)OR you could opt for a sodium bisulfite injection with a small metering pump to accomplish the same thing on the downstream side of your process.

If you still wish to have an RO system and reduce the amount of water discharged, that is a valid argument BUT you still have to de-chlorinate the water prior to inlet of RO system to prevent membrane damage. Consult with a local professional, when all else fails follow wisdom.

James,

We're in So Cal (LA County). The state requirement is for our local area (each area has a different maximum chloride level). No road salt out here, just a lot of sunny warm winter days, so no problem with runoff.

The Dept of Sanitation has one option, which is to use UV light to "clean" the waste water before dumping it into the river. Our source water comes from our local lake and underground sources. The federal level of chloride for potable water is 250 mg/L, which was set due to taste, not health levels. Our drinking water is well below this level.

Our treatment plant treats 20,000,000 gallons per day, not 20,000 gallons. Since we're looking at chloride vs chlorine, I don't think activated charcoal will work and I think RO is one of the best options.

Then unfortunately, you will be stuck with the cost of a fairly large RO plant. What, pray tell do you intend to do with the wastewater from the RO plant? You could water a golf course perhaps. You will need to ppurchase an RO plant that can treat 10 MMgallons/day (~38000 m³/day). You will then back blend the RO permeate with the remaining wastewater going to discharge. By the way, if the RO system has a recovery value of 75% (typical in many instances), then it must be supplied 133% of the product, namely 13.3 MMgallons/day. You will have the remaining 3.3MMgallons/day of RO concentrate to dispose of - probably thru irrigation of parks and golf courses. Some golf green grasses may not tolerate the higher salt content as well, but with ample watering many of them will thrive. Another option (if you have a basin nearby that could make a natural lake), would be to fill a small reservoir for recreation purposes.

James, The options that we were given are in my original post. Namely, dumping it underground, trucking it away or building a pipeline.

I think the whole thing is crazy and I feel that our reps need to go to the state and request a change in the outgoing chloride levels.

Of note, in the past, they have requested raising the levels, but I don't think they made a strong presentation.

You're right, there needs to be a State wide standard for safe levels at the end of the treatment.

Maybe you could raise salt water shrimp in it! Sell them to cat food companies.

It is always worth your while to look into something like what Millwakee does with their Milorganite.

You could still come back to them with the alternate proposal: instead of holding in underground storage with a trickle to the strata below, you could introduce a reasonably salt tolerant grass such as coastal bermuda, and land apply the wastewater (RO concentrate only) to produce grass for a local dairy, or a herd of goats, then every one can have cabrito (BBQ goat).

Cost of AgCl may not be much compared to interest depreciation and running costs of an RO or other treatment systems. Considering the large volume of an open sea, the extra nitrate even at 75 million litres are so will not affect marine biology. Thunderstorms put much more nitrogen into the sea.

AgNO3 precipitatin can be checked out easily in a beaker in the Q/C lab for feasibility.

Very Interesting. Do you know any existing facility which use AgCl precipitation as a means of treating waste water to reduce Chloride content. I believe you propose to use AgNO3. As one will never be allowed to precipitate 100% Silver, what is the safe ppm (or ppb) allowed in treated water for marine biology?

More silver than you would want to afford!$$$$$

So just to verify, are you saying that if you can treat the waste stream to potable standards you will be allowed 250 mg/L???

Then ozone/H2O2/UV combinations will be much more effective than straight UV to kill pathogens as well as reducing BOD.

JNB, No, we are still stuck with 100 mg/L. What is being proposed is a treatment of our waste water to remove chloride. The pathogens are not an issue, as they are treated at the water treatment facility. The water coming out of the water treatment plant is dumped in the river and when it reaches the farms, some is pumped out to be used to irrigate the crops. The farmers are pushing the state to enforce the 100 mg/L chloride limit. They are claiming crop damage from the chloride levels.

Dilution is the solution to pollution!

Treatment of ChlorideReverse Osmosis will remove 90 - 95% of the chlorides because of its salt rejection capabilities. Electrodialysis and distillation are two more processes that can be used to reduce the chloride content of water. Strong base anion exchanger which is the later portion of a two-column deionizer does an excellent job at removing chlorides for industrial applications.

another alternative:

http://water.usgs.gov/wrri/00grants/99pdfdocs/NewMexico4.pdf
even better...
http://www.nist.gov/tip/wp/pswp/upload/88_centrifugal_hyperfiltration.pdf

If all chloride salts be made Sodium Chloride, then how about drying in Solar ponds and sale the salt? You need to concentrate RO reject of first stage to further put through RO, to increase salt concentration of final reject water and as feed to solar ponds.

Aeration ponds would get rid of the chlorine but you would still have the sodium.

http://www.gizmag.com/salt-tolerant-crops/12253/

combined with:

http://www.trojanuv.com/resources/trojanuv//Backgrounder/TrojanOVERVIEW_singles_LR.pdf

and the second link in Reply #46

Then sell the RO waste water to the oil companies to use for fracting in natural gas wells!

That way they won't be dumping good drinking water down those wells were it will be lost forever.

Eventually the oil companies will be building huge RO and off shore evap rigs and then they'll sell us water at $5 a gallon once all the cars are alternative fueled.

one of these methods might be online by now...

http://gizmodo.com/5990876/lockheeds-new-carbon-filter-takes-all-the-effort-out-of-desalinization

http://ngm.nationalgeographic.com/big-idea/09/desalination

This from Wiki on Wastewater Recycling...

http://www.beachapedia.org/Wastewater_Recycling

Understanding and implementing water recycling requires a paradigm shift from thinking of "used" water as wastewater (something to get rid of as cheaply as possible) to thinking of it as a valuable resource. Existing, proven technology can be used to convert water that has previously been flushed down your toilet into drinking water that meets all applicable water quality standards and is probably purer than most expensive bottled water.

An example of just such a facility is the Groundwater Replenishment System in Orange County, California. There, about 70 million gallons per day of wastewater that has gone through primary and secondary treatment at Orange County Sanitation District's "Plant 1" is piped to a facility next door operated by Orange County Water District. The water then is processed through three additional purifying steps, using microfiltration, reverse osmosis, and advanced oxidation. At that point the water is pumped about 15 miles to spreading basins where the water is allowed to percolate through natural sand into underground aquifers. Wells then draw water out of the aquifer to be used as a fresh water supply. That system can be thought of as a continuous loop or a "man made" water cycle.

...100% recycling is possible. Cape Coral, Florida recycles all of its wastewater during some years. A few years ago the city launched a half-billion dollars worth of water and sewer treatment plant expansions to treat wastewater and pump it back through the city's irrigation system. This protects their waterways and assures the city has a reliable water source all year...

http://www.fwrj.com/techarticles/0909%20FWRJ_tech2.pdf

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I live near Cape Coral and have built houses there for other people and every yard has two water meters, one for inside the house and one for lawn sprinkling.

The one for the irrigation water costs the homeowner $5 a month and has unlimited use. There is a substantial impact fee for new homes and they did pass on the cost of the new plant to everyone in Cape Coral. Fort Myers, which is on the other side of the river, has just recently voted in a pipeline over to the Cape to get rid of treated water from two of it's water treatment plants.

The treatment plant on the south end of town uses the large open ditches along several miles the crosstown expressway to natural filter it's treated effluent (it is VERY flat here!). Tourist season usually puts things at their maximum capacity and they used to dump into the local creeks leading into the back bays of the Gulf of Mexico but recently they had to stop doing that too, hence the pipeline to Cape Coral which hooks up to their treated water irrigation system.

City of El Paso NW water treatment plant also uses advanced technology, including a final ozonation to recycle treated wastewater to the Hueco Bolson (aquifer). They included some type of tracer (ion) in the water (that is harmless), the water is injected on the "far" side of the aquifer, and water is pumped from the "near" side. Thus it went on for years, and in at least a decade (this has been fifteen years ago now) no tracer was ever recovered from the pump stations. It is a large aquifer.