Ceramic Water Filters 101

By: Rachel Schmidt

Who am I?

Helllllllo Team!   I’m so excited to be writing a guest blog for H2dayO!  My name is Rachel Schmidt, and I know Ariel from our civil engineering days at good ole UVa (University of Virginia)!  We took many classes together and spent a summer working with families and slow sand water filtration units in La Gracia, Belize.  I have yet to meet Monique – but hopefully somewhere down the line!

South Africa

So let’s get to the good stuff… I’ve recently returned from a 9-month Fulbright Grant in rural South Africa. I was working to further develop and establish a Ceramic Water Filter (CWF) Factory.  The two big-picture goals include: 1) Get clean water into the community (along with awareness and sanitation education to help prevent disease), and 2) Revive a local business so the workers can produce a profit to support their families.

The Team

I worked with a large UVa-based team, led by Professor Jim Smith, as well as a sizeable University of Venda team, located in Limpopo Province, South Africa.   The multidisciplinary teams include students and staff from anthropology, architecture, biology, business, engineering, and nursing, among others.  We worked closely with a Limpopo-based women’s organization known as the Mukondeni Pottery Cooperative.  Together, these teams make up our newly founded organization, PureMadi – check it out here: puremadi.org…  Pure is for purifying water, and Madi means water in the local Venda language, Tshivenda!

Mukondeni Pottery

The Mukondeni Pottery Cooperative began over 25 years ago with a group of women coming together to teach ceramic skills and develop a small business.  Today, Mukondeni has grown to include 40+ women, a large building to work in, and an expansive outdoor display area (see Figures 1 and 2).  Due to poorly maintained roads and increased competition in the area, Mukondeni is finding it difficult to sell enough pottery to make a profit.  The ladies’ knowledge of ceramic artistry, current financial outlook, willingness to try new technologies, past relationship with the University of Venda, and local survey data resulted in the Universities approaching them to join into a mutually beneficial relationship.

Ceramic Water Filter Technology

Ceramic water filters originated in 1980, and were streamlined in the 1990s to be uniform in size (think flower pot shaped) and capability.  Laboratory and field-testing of CWFs has determined they are highly effective in reducing waterborne pathogens and disinfecting harmful bacteria.

Materials included for CWF production: 

a) Clay – found and mined locally

b) Water – provided by on-site borehole

c) Sawdust – provided for free by local lumber mills

d) Silver nanoparticles – provided by UVa team

Process to create CWFs:

1)       Dry clay and use electric hammer mill to grind clay into a fine dust

2)       Dry sawdust and sieve down to desired size

3)       Add fixed ratio of clay and sawdust into electric mixer, then add water

4)       Use hydraulic press to mold filters into uniform shape (see Figure 3)

5)       Allow filters to dry, and fix imperfections and rims

6)       Fire in wood-burning (or electric!) kiln – this allows the sawdust inside the filters to combust, leaving small pores in the media to allow water to filter through – thus handling the physical decontamination

7)       Perform the pressure test (make sure there are no cracks), and the flow rate test (to ensure water spends enough time in the media to be effectively filtered, but isn’t too slow to prevent usability!) for quality assurance (see Figure 4)

8)       Dilute silver solution, and paint onto each filter – this takes care of the chemical disinfection of the filtration process (see Figure 5)

9)       Prepare bucket by rinsing it out, drilling and inserting plastic spigot, and slapping on a sticker

10)   Place filter in the bucket, snap on the lid, and you’ve got yourself a ceramic water filter



I reached a few major challenges…

1)       Language:  Tshivenda is a difficult language to learn, as it doesn’t translate well and includes noises I have never made before.  A few of the women spoke English, so we all gained patience and understanding while learning to connect and communicate effectively.

2)       Culture:  Communication was not only difficult due to the language barrier, but to the cultural differences as well.  On multiple occasions, I encountered vastly diverse cultural expectations, which often to led to severe misunderstandings.  These differences were difficult to cope with, until I recognized the situation and could work harder to stay transparent and keep folks updated.

3)       Roof:  The roof of the open-air factory blew off during a huge storm!  Luckily, no one was at the site or harmed, but it put a one-month delay on filter production.

4)       Press:  Two of the three filter molds dented during pressing, which left us with a multi-week delay to get them re-fitted and filled with concrete.

5)       Kiln:  The wood-burning kiln was very difficult to work with, and rarely reached 900C, resulting in unacceptable filters.  WOMP.  I was not able to master the balance of stoking, airflow changes, timing, or teach the concept well enough.  We ended up re-furbishing an old electric kiln that had been on site since the 90’s.

Wrapping Up…

All in all, my work in South Africa focused on structuring and perfecting the filter-creation process, ensuring that the women could produce filters independently, and helping them get their business off the ground.  I worked with the Cooperative Manager to engage additional stakeholders, initiate a marketing program, distribute our first batch of filters, and provide trainings for all of the women.   The Universities and I remain committed to Mukondeni for the long haul, even once we have reached an acceptable level of independent sustainability.

There you have it…. the super basics of starting and maintaining a ceramic water filter factory!  It was a wonderful experience in which I formed amazing friendships with these women, learned the technical nitty-gritty of CWFs, practically started a small business, and experienced living abroad!

Chlorine gas a thing of the past! Electrochlorination is NOW!

Chlorination began in the early 1900’s and since then diseases such as dysentery, cholera, and typhoid have significantly decreased to almost 0% in 1950. It was a very impressive discovery with tremendous affects on sociey. Since then, electrochlorination is a newer more updated way to treat drinking water. It does not harm the environment and does not have any by-products like basic chlorination has. It is much safer to handle, is nontoxic, relatively easy to make and is a more natural way to treat drinking water.

Electrochlorination runs an electrical current in salt water to produce hypochlorite. It is considered to be a type of desalination and is a rather simple process. Saltwater is put into electrolyzer cells (after solids are removed). It is then moved through various channels that range in decreasing thickness and are charged with positive and negative low current DC. The reaction is a production of sodium hypochlorite and hydrogen gas, which has between 0.7-1% chlorine. It uses chlorine, a very common drinking water disinfection, in a hypochlorate solution that is dispersed within the system. The hydrogen gas is then removed and the solution is stored. It uses no chemicals!!

Electrochlorination follow this simple equation:

NaCl + H2O + Energy -> NaOCl + H2

Electrochlorination systems are usually used by large water utility companies before the water is pumped to households, but it is becoming more available to smaller populations and there are several installation engineering companies that design specifically for the clients needs .

It has several advantages:

  • Low costs
  • Used worldwide
  • Nontoxic because it is salt based
  • Easy to store
  • Safe to produce
  • Low maintenance
  • Long life cycle
  • Approved as a disinfection from the CDC
  • Reduces scaling because of a lower pH

Disadvantages are:

  • Effects biofilm in hot water pipes and tanks
  • Effect on bacteria is limited in the long term
  • Smell and taste is changed
  • Less effective with pH’s higher than 7.5Image

NOT too bad huh?!

Life Straw! Mini Water Purifier

My dream company to work for!! One day, one day… Check them out, absolutely incredible!!

Awesome Stuff To Buy Online

This is really neat invention that will allow you to drink water from questionable sources when you’re out on a long hike and don’t want to carry too much weight. It filters at least 99.9% of waterborne bacteria. This is very impressive but expected if you are filtering particles up to 0.2 microns.

Considering it’s only $25, it’s a great buy for anyone that likes be out in the wild for longer periods of time. You never know what may happen and water is a first priority. Although not the worst of the 7 enemies of survival, it surely will kill you the fastest and it is only a result of poor planning and preparation!

This lab instructor has balls enough to use this straw to drink from poo water! Watch Video

If you check out their Website, it looks like they have more plans than just using the…

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Innovative, creative, and simple ways to can water good enough to drink!!

Innovative, creative, and simple ways to can water good enough to drink!!



Engineering crush: Green Roofs

I thought I would write my first ‘spotlight on a technology’ post on…. Green Roofs! It’s because they’re so great. And because I intend to live in a house that has one (if I don’t end up living in a tree house).

What a Green Roof is…

They are multiple layers of soil and plant matter that are installed on the roof of a building. Basically, if all houses and buildings had green roofs, we’d be living in the Shire (minus the hairy feet).

The forest is really good at dealing with storm water. Rain falls on a natural area relatively evenly and it percolates down into the soil. Effectively 100% of the ground is permeable so the water can infiltrate down into the groundwater system (recharging aquifers! Yay!). When an area is built-up, however, rainwater gets erratic. It will run off traditional roofs and onto paved, impermeable sidewalks. If there is no drainage system, flooding will occur. That’s bad. Also, even if there is a drainage system it may be old. Old systems tend to just siphon off the water into nearby lakes or streams. These natural water bodies haven’t been adapted for influxes of large volumes of water. Their delicate stream beds and shores may begin to erode due to the water’s force.

So if you put a little forest on your roof (that’s what a Green Roof effectively is) you can restore the natural process of rainwater movement through our environment. You are protecting streams and lakes! You are helping prevent flooding! You are planting trees and greenery which gobble up CO2! Also, they look pretty boss.

Can I get one?

Yes. I’m glad you asked. There are varying thicknesses of Green Roofs that you can install on your roof. Even a thin layer of soil and plant matter (generally called an “extensive green roof”) can help manage storm water. And it won’t be crazy expensive or require a retrofit to support the added load to your roof.

See, you can even graze your goats up on these bad boys.

I want to learn more!

Go here: http://www.greenroofs.org/grtok/index.php

And here: http://www.ecogeek.org/architecture/894

“Ecogeeking” out in D.C.,


Desalination, not really the way to go?

I have heard so many times people not caring (especially in Hawaii) if they overuse/waste water because well, there’s a whole damn ocean that some engineers can figure out when/if we ever need it. Yeah, because with the way we consume water in this country and with hundreds of millions of people living within a drought-ridden area, it’s GOING to happen. It IS happening. Ever heard of the water crisis?? The key to changing this incorrect point-of-view is to learn what the process of desalination is actually about to see if it is the appropriate alternative for your area and then change behavior to CONSERVE water! Wow, that is going to be very difficult.

In the past half a century, there has been a huge increase of technology dedicated to decreasing energy consumption. Unfortunately, desalination has an incredibly high demand of energy, emits green house gas, disturbs local marine environments, is an excuse for our poor behavior, etc., so why backtrack? More attention and funding should go towards preserving what clean fresh water resources we have left rather than push for alternative methods to continue our exuberant rate of consumption.

There are two popular processes of desalination, multi-stage flash distillation using heat to evaporate water leaving the salt behind (dirty, dirty, dirty) and reverse osmosis desalination that pumps water through filtration membranes (cha-ching, lots of money).  Then, what do you do with the concentrated salt stream that is produced as a result of multi-stage flash desalination? How do not damage the environment with such a volume of salt? Yes, plant designs take this into consideration and in the U.S. and Europe an EIA/EIS would determine whether the consequence is a concern or not. However, what if desalination is only used for extreme situations, such as along the equatorial belt where there is a high proportion of drought and poverty?

There are facilities such as, inland desalination plants like in El Paso and a lot of rich countries like Saudi Arabia, China, U.S., Israel, UAE, etc. all do it already. But to complicate the problem further, who is going to fund these large projects, especially in developing nations? Then the conversation gets really political and someone is always going to be left out especially if they lack the mineral/resources to attract outside investors. So, solution is easy… hold off on the desalination excuse and start conserving water.

Here in the U.S., City & Country, State, and Federal policies should focus on Reuse facilities and demand golf courses, toilet water, agriculture, etc. use recycled water. That would save up so much of our clean fresh drinking water. There are also easy solutions out there such as storm reclamation and rainwater harvesting; we just need our policy makers to understand the alternatives. The technology is there, the engineering capabilities are there, we just need to do it.