Technologies for Recycling Laundry Water

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Technologies for Recycling Laundry Water

I have a customer who asked us to help them to recycle the water used in the laundry process (washing clothes and linen). They want to use the water in the laundry process again once recycled.

The daily water usage is 600 liters per day total from 7 different industrial type washing machines.

Can Ultra Filtration and Carbon Block technologies recycle the water back to the desired state? 

How about the soap and bleach elements, how to take care of these?

How many times can the water be recycled through this process?

Any advice would be appreciated.

Please, no general product/brand sales punts.

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32 Answers

  1. one of the main issues with laundry water reuse is the concentration of lint which needs to be filtered out. Also I would imaging that your client will want to retain as much of the heat as they can, which is where RO fails as the membranes typically fail around 45c. I would look at using an Organic Destruction Cell, as it will remove micro pollutants, and organics at a higher temperature.

  2. Hi Shawn.  Laundry wastewater requires biological treatment to remove the soluble organic contaminants from the soap and detergent, but biological treatment can be problematic in North Americaas a result of low phosphorus detergent formulations.  As a consequence, if treating laundry wastewater on its own, nutrients generally need to be added to support biological oxidation.  There are a number of ways to approach treatment.  You could consider electro-coagulation or chemical coagulation/flocculation to remove suspended solids and colloidal solids prior to biological treatment, followed by filtration (possibly MF or UF membranes).  Like any industrial wastewater treatment process investigation, pilot testing is highly advisable due to the extreme variability between laundry operations and wastewater characteristics.  RO membranes have also been used, but typically reject around 25% of the wastewater flow to sewer - so water conservation levels are much lower than using more conventional treatment.   The degree of treatment required greatly depends on what level of residual contaminants may interfere with laundry cleaning efficiency.  Biological treatment with ceramic micro or ultra-filtration membranes have also been applied - but the ceramic membranes are still very expensive.

     

  3. Some new information:  (1) Waste water produced is closer to 700Kl per month. (2) Recent water tests results received **note Main Laundry results**. 

    1 Comment

    1. That seems more reasonable.  We could design a 20-25 cubic metre per day system using ultrafiltration in an MBR certified process followed by AOP.

      Commented on by

  4. 600 LPD does seem a little low.  However, we are able to scale to this size for laundry closed loop recycling.  Yes, ultrafiltration is used.  It is used in conjunction with membrane bioreactor process.  We then follow with an advanced oxidation process (AOP) which involved ozone and UV.  Our process scales from 300 to 50,000 LPD

    Answered on by

  5. 600 LPD does seem a little low.  However, we are able to scale to this size for laundry closed loop recycling.  Yes, ultrafiltration is used.  It is used in conjunction with membrane bioreactor process.  We then follow with an advanced oxidation process (AOP) which involved ozone and UV.  Our process scales from 300 to 50,000 LPD

    Answered on by

  7. I'm not 100% sure, but quietly confident that your bleach  and soaps would be taken out of solution with electrocoagulation. In this "oxidised" state it would be very easy to separate and then filter the cleared water for reuse. Worth a test at least if you have access to a pilot scale EC unit.

  10. The simplest type of greywater use is to collect water in a dishpan as you handwash dishes, and then toss it over your flowerbeds or fruit trees. This is a wonderfully simple, inexpensive way to tap into greywater, but with just a little more effort and expense, you can capture much more water.

    Greywater is household wastewater from bathroom sinks, showers, tubs and washing machines; it has not come into contact with faces or passed through a toilet. Some intrepid homeowners recycle their greywater by using it to water their lawns or gardens or by using it to flush their toilets. The greywater can be treated first, or it may be used untreated; under no circumstances, however, should it contain bleaches, dyes, bath salts, fabric softeners or detergents containing boron — an excess of boron is toxic to plants.

    1. All required laundry detergents and auxiliary washing preparations are fed into the line over a dosing system by computer control as well as the water is added.
    2. The washing water is thermally and biologically processed after the washing operation, so that the cleaned water can be fed back again into the washing circulation process. Therefore, the laundry procedure does not generate any wastewater.
    3. The process exhaust air of the washing operation is being used to produce energy – it is re-fed into the process (laundry line, dryer) again as steam for recovering heat.
    4. A thermal afterburning system emits the waste exhaust air after treatment as „clean air“to the environment. The exhaust air from the drying process is used for recovering heat for the dryer. Waste exhaust air is being emitted as “clean air” to the environment after the treatment in a regenerative afterburning system.
    5. In order to build the LWR you need to have room directly (or nearly) above your washing machine for the tank. You also need a way to secure the tank safely, because when full it will weigh more than 250 pounds. 

  11. Hi! Shawn, 

     

    Typically industrial/commercially consumes 18/26 liters per kilogram of linen washed. So if the laundry is using only 600 liters per day on 7 washer extractors, it might be small  domestic washers. 

    And such low water quantity the recycling would not be cost effective. Usually  a 7 industrial washer extractor with minimum of 2500 kgs/day can be very ideal situation of recycling with fair payback. 

    We do laundry waster water recycling with proven technology and our customers have saved over eight billion gallons of water. 

    Let me know if you need more information on our product line.

    Best regards

     

    Suresh Pillai

     

     

    1 Comment

    1. I totally agree with you, Surej! One of our clients consumes 10m3 per day per machine. 600 L with 7 machines is not indusyrial like and as I mentioned in my post, not economically viable.

  12. The first wash water will be dirty and needs to be drained. The next  rinses should be collected. Followed by simple flocculation and sand filtration (incl back wash) + UV and than reuse. 

     

    1 Comment

    1. Yes. I think some form of synchronization with the washing system will be required to optimize size and energy consumption of the recycling system. That is assuming it is on industrial scale. I think feed buffering is definitely a requirement for the washer system.

  13. We have also been requested by our friends to help them find ways to reduce the wastage of water in the laundry process. The requesting unit processes about 30KL- 40Kl of water per day. they shall be interested in bioremediation techniques to extract raw water for the initial rinse cycles. Suggestions may please be sent to pk@jugapro.com

  15. Hi Shawn, Is there a standard flow rate?  Pulses or continuous. I would think with 7 machines, probably not synchronized, would have huge fluctuations in rate and duration (24/7?). My context is ecological design using siphons, basins, and continuous flow tanks for organic breakdown of the compounds. With this the volume is buffered and collected for continuous flow in a series of tanks. Much like water systems in the water short islands, the water is recycled. Very low energy, clean water for reuse, high organic output, and a PR benefit too. It takes space and a strategy that begins at the start of the washing process.  Low cost ecological system.

  16. Hi Shawn, 

    I work in a membrane factory, we manufacture and sell UF membranes, and we have the experience for filtrate laundry water. We can discuss on this project further by email, my mailbox is: export006@aqucell.com. Wait to hear from you.

    Best Regards,

    Linda

    Skype: live:export006

    Wechat: 008618871589928

    Email: 008618871589928

  17. I design eco systems closed and semi closed. If I understand you correctly you have a chlorine problem. (chlorine filtering must be part of step #1)... suggest cupric sulphate.  This coagulates and makes it easy to remove without expensive filters.  Next would be a selection from which to choose. You can use the remaining water for agricultural use, bio toilets, or venture towards 100% recycling of your water using a biodigester with a bio generator.  When using RNA microbes for bio degradation electrons break away and be collected for your energy needs.  Collect, use, long term storage of rainwater is always a plus.  Then you can grow food for yourself and your wash customers. Maybe open a restaurant on location. Talk about a captive audience.  wash, eat, learn natures bio systems that cost you zero.   contact me for details on all of the above.   

    1 Comment

    1. The one-all-solution sounds very interesting without the regulatory concerns. 

      1 Comment reply

      1. regulations are the concern. They interfere with the natural process. The only purpose for any regulation is to make money. Take from the poor and give to legislators and their corporate accomplices. These microbes have been used for the last 40 years. Passed every inspection. Declared 100% organic.  Can be shipped and used with any country belonging to the WTO. But seeing how they eliminate the need for regulations and our EPA these criminals infest every part of our society.  Cochroaches all.

  18. There are several companies specializing in recycling laundry wastewater. One of the best is Pure Pulse marketed by Water Recovery System. They employ a ceramic membrane process. As well saving water it also reduces energy consumption. Google Pure Pulse

  19. Hi Shawn,

    A simple system commonly known as a laundry to landscape system could be optimised to industrial scale if need be. Laundry water either for reuse in Laundry or for use in irrigation.

    The laundry to landscape system allows for a limited number of trees and shrubs to be irrigated by utilizing the built-in pump within the washing machine. The water pumped from the washing machine is unfiltered and is simply dumped onto the plants and trees. Valves are added to provide some flow balancing to the system. Because the greywater is unfiltered it is mostly not used in drip irrigation systems. 

    Also, using ozone has over time proven to be inefficient and expensive especially on a large industrial scale as for oxidizing these soluble pollutants. Use of biological treatments is presently gaining sway and is most sustainable for this process.

    1 Comment

    1. Hi, Amali, Could you please indicate studies on "using ozone has proven to be inefficient..."? Expensive, yes, I admit, but inefficient.?, Where are the facts based on data?

      1 Comment reply

      1. Hi Pedro.
        I am not an expert in this field but it is of concern to me and I have had to read lots of related literatures assessing the system functionality. The efficiency of the system often comes into question due to the need to maintain an optimal ozone dosage. Low dosage may not effectively inactivate some viruses, spores, and cysts. And because the concentration of ozone generated from either air or oxygen is so low, the transfer efficiency to the liquid phase is always a critical economic consideration.

  20. Hi Shawn,

    First you need selfcleaning fine screens or sieves to retain and remove fibers and other large solids which would otherwise result in clogging and damage downstream. Next a gravity trap shall remove the sand/grit upstream of a mixed buffer/equalisation tank where the bleach will decompose in short time (depending on wastewater temperature). UF as proposed by others will only remove solids. As a result all soluble pollutants including smelly volatile compounds would be recycled. Using ozone would be very inefficient and expensive as main treatment to oxidize these soluble pollutants. Instead we use advanced biological treatment as most sustainable and efficient main treatment followed by UF and ozonation as polishing.

    Regards, Bruno

  21. Shawn; the issue will be temperature, TSS and oils and grease. since the water recycled will come from various sources the opportunity for cross contamination and "surprise"  feed water changes will be a common occurrence, standard PVDF UF membranes will not be tolerant to this and will fail quickly. Most recycle operations utilize a ceramic UF to tolerate the higher temps and oils. Cost would be prohibitive for a 600 l/day system. You can use carbon block and standard filtration to treat the wash stream and reuse the water in the rinse cycle. some sort of dosing will be required to control chemistry and odor. Typically you will see a 50-60% reuse rate before you start to get diminishing returns. ljessup@kemcosystems.com

  22. I am no expert on treatment of this industrial effluent, but home laundry would have grit and solids, organics, fecal coliforms, and detergents, at least; in lower concentrations than domestic sewage, but similar in general quality. The detergents are certainly biodegradable. I did lots of experiments with them in graduate school back in the day. That suggests that biological treatment may be a more cost-effective solution than chemical treatment, especially if life-cycle costs and environmental consequences of the manufacture of the chemicals are considered. Could be a good application for a membrane bioreactor. The UF membranes may do a good enough job at disinfection that post secondary disinfection may not be required.

  23. Hi Shawn, glad to make an introduction to Chris Gilreath, CEO at Recycled Hydro Solutions as he should be knowledgable about your concerns and able to expertly comment. RHS use a process to strip bacteria from "dipper wells" in ice cream shops. Let me know now how to connect you, via Linkedin or per e-mail and revert. Disclosure; I have no affiliations or interests in RHS. He is a personal friend through the Cleantech Open.

    Cheers, Bert

    Answered on by

    1 Comment

  25. Hi Shawn,

    we have some experience on Ultrafiltration use for industrial washwater recycling (not exactly laundry). Recycling reasonable portions of the water used is working well, non-bound detergents could be recovered as well but not the detergents bound to the waste. Maximes hint on membrane materials is helpful, no doubt. The amount/concentrations of phosphate you have to deal with is highly depending on the place of our globe your plant is working. We have very low phophate concentrations in EU wastewaters, but that is not the case in other regions. As phosphate is able to pass the UF membranes you should not have any concentrating effects leading to scaling even if you have that high amounts mentionend by Oksana.

    Keep us updated and hope I could help,

    best regrads

  26. UF would be a great solution to recycle 70-80% of the volume and soap and heat however at 600l/day  would the investment be viable? The condition are ideal for UF too hot effluent low TSS be careful with oxidant on polymeric membrane but most of all fibres textile fibres that can rapidly clog spiral configuration

    reusing the rinse water for the next washing cycle is a great idea & easy. Both could be combined.

    600L/day may not warrant a UF system 

  27. In the USA many people use ozone technologies. Chemical free and very effective.

  28. It may be simplest to reused the rinse water for the next wash cycle.  This would probably save half of the water used.

  29. The best way we use is a simple gravel filled greywater wetland system. This is a proven and very effective system to achieve all you want. Contact me if you want more details.

  31. Hi Shawn,

    This isn't my area of expertise, so I haven't got a perfect solution for you. Instead here are a few comments that might be useful.

    Ultrafiltration is probably the right direction to go. This will generate a concentrated waste stream, so you cannot recycle 100% of your wastewater. The goal shouldn't be to eliminate all liquid waste, but to reduce fresh water intake. You're probably looking at 60-70% recovery, very rough estimates.

    Be mindful of the types of membranes you use. Bleach will damage typical polymeric membranes. May be worth looking into ceramic membranes, more costly at purchase, but cheaper in the long run. Activated carbon may not be required at all with the right membranes.

    I hope this helps!

  32. as far as I know from that article http://file.scirp.org/Html/2-2200743_41855.htm
    Phosphate was detected in 93% of the samples (94.65 mg∙L−1 average); its strong presence was most likely due to the laundry water contents.
    We have tested Vortex Layer Technology to remove phosphates from wastewater
    here is the link to video-report https://youtu.be/jMmrMCwZdf8
    and full article is here https://avs.globecore.com/removal-phosphates-waste-water.html