Water Technology vs the Coming Population Explosion

The primary lack of investment in infrastructure for water is, in my opinion, due to the fact that there is an almost universal belief that every individual has a "right" to clean water, and that it is someone else's responsibility to pay for it. It costs money to collect and treat potable water, and it costs money (and usually a pretty good chunk of land) to treat most of it after we flush it down the drain.

Add to this the fact that urbanization has a profound impact on natural water flows, and the picture gets even scarier. Build a house or pave a road, and land that once absorbed water and passed it on to the aquifer is no longer able to absorb the water. Where does it go? Runs over a contaminated surface, picking up all sorts of contaminants like oily residue from automobile exhaust, tires, insecticides and what have you. Someone somewhere downstream is now going to have to spend a whole lot MORE money rendering this run off suitable for anything more than flushing toilets. Boiling your water is only going to go so far- lots of nasty stuff will still be left behind. The only real solutions are very high energy intensive processes, which only tends to compound the issue...

Conservation. When water becomes a commodity that people must pay for it will not be so callously wasted. The worst waste is the pollution of clean water with human and industrial waste. But there are other kinds of waste starting with the western habit of cultivating decorative landscape plantings and intensively watering them.

A state of the art sewage treatment plant takes up much less than 1% of the area of a modern city. It is hard to believe that the level of commercial operations that exist in any city cannot support the cost of a safe water supply including proper waste treatment and a simple part of doing business the same as cost of maintaining law and order.

Another thought here. Much of the load on a sewage treatment plant (and resultant negative effects on downstream water supplies) comes from material added to the waste stream that doesn't belong there and is better disposed of in some other selective manner. Suitable education and motivation of the city population and development of enabling technologies for waste separation as well as recycling may well solve a lot of the problem. A cultural intolerance of "filth" ought to be given as much priority as the accumulation of wealth. Some nations do quite well at this. Others are woefully inadequate. A high tolerance for political and commercial corruption seem to go along with the latter.

Ed Weldon

Water conservation by minimizing waste of water. Avoid deforestation to allow the nature to do its duty i.e. enough rain to keep enough water table on earth. Cost effective waste water recycling .

Rain harvesting in all type of building to regenerate the ground water. Low cost membrane technology to convert sea and brackish water as potable water. Improvement in the Combined Hear power technology ( CHP) to reduce cost of desalinated water.

Rain harvesting is not a good idea in urban areas- vehicle exhaust seriously contaminates your collection surfaces. In rural areas, it provides the best quality water available, but one must concern oneself with controlling mosquito breeding, and, quite often, maintaining the water quality for extended storage periods. These are relatively easy things to accomplish.

But, I don't think you want to drink rain water collected in an urban environment...

Avoiding deforestation is a key element to protecting one's water resources.

Thermal power plants -- both coal and nuclear -- waste a lot of fresh water in evaporative cooling of turbine exhaust steam. Once-through cooling (which avoids the use of cooling towers) is encountering resistance (cf. Indian Point) over concerns of thermal pollution and fish kills. Air cooling just does not have the capacity for cooling at utility scale because of the low heat flux possible through fins, even assisted by blowers.

As the world becomes accustomed to electric cars, refrigerated food storage, data centers, air conditioning, and the other conveniences of American-style prosperity, the demand for power generation will certainly increase, and therefore water consumption will become an even bigger problem. Currently, power generation water consumption is second only to agriculture.

So, any ideas about reducing the water waste at power plants?

*In future there will be a new category of water source called reclaimed water[ treated water].

* Water will be aptly replaced in many of the uses including washings.

* Sterilized recovered water will find use wherever applicable.

* Future waste water treatment industry will be more towards elctro chemical based technologies.

* Treated water will replace fresh water for Agricultural usage.

* Membrane technologies will continue for potable water supplies.

* The situation is well under technology scope ,control provided cost sustainability is met with.

The key is "provided cost sustainability is met with..." Membrane technologies are very energy intensive, and costly. Most effective waste water recovery systems are energy-intensive and costly. Many people in the world think water should be free, but someone has to pay for the infrastructure and the cost of operating these systems. If one choses to rely on government to maintain the water supply at adequate levels, then taxes go up, or other services suffer.

The technology exists to keep us in water. What is lacking is a true appreciation within the general populace of the true cost of providing this water...

Low Cost Electricity is the key in water treatment systems.

The present trend is towards Waste water treatment plants with electricity generation capability.

Even chemical coagulants need to be replaced by electrode based technologies in order to ensure sustainability of mass chemical coagulants.

"Low cost Electricity"- the Philosopher's stone. Self-generating for treatment plants can potentially reduce the cost, but it is unlikely that one would generate sufficient energy to completely supply the facility. Other alternatives, such as wind and solar, are not generally cost effective, although under certain specific circumstances they can help reduce costs.

One issue with waste treatment is it takes TIME. A major concern here is that, with rapid growth in urban centers (and growth in the prosperity of the served population), the waste stream grows far more rapidly than planners had anticipated- which means most facilities are not designed for the volume realized- ergo, inadequately treated waste water being re-introduced into the environment, further compounding the problem of availability of suitable potable water. Independent of cost of energy are the capital costs required to expand facilities to meet the growing demand. It is very difficult to convince your population that they should invest tax dollars to insure that downstream, unrelated populations have access to potable water...

"It is very difficult to convince your population that they should invest tax dollars to insure that downstream, unrelated populations have access to potable water..."

This is one of the reasons why we form formal communities (states, nations, treaties, etc.) and govern them through systems of laws. The idea is to keep one group from taking advantage of another.

There are a number of places in the world where the same river flows through two nations. They are places facing real shooting wars over water in the future if suitable water rights measures are not implemented earlier.

Something that hasn't been mentioned here is that we have old biofilm technology for sewage treatment such as trickling filter systems that are very effective for secondary sewage treatment. The downside is that such systems require more land space.

Their use of energy is primarily to move the sewage water through the stages of treatment. If sufficient gravity head is available the energy requirements are minimized. Energy to drive comminuters in the primary treatment is still needed; but that can be minimized with reasonable control of the solids that go into the waste stream when uneducated people use their toilets and kitchen drains as general waste disposal for solid material that would better go into the solid waste garbage stream.

In the above mentioned system a well managed sewage plant combined with an educated and motivated community which it serves can minimize the amount of expensive tertiary sewage treatment needed before the effluent stream enters natural waterways or is in turn returned to processing for domestic and industrial water consumption.

By the way, and this is off topic, I have plenty of general housekeeping experience to support a position that the individual home is where the world's problem with shortage of domestic potable water will be solved. We have a septic tank system that has gone 25 years without requiring sludge pumping service. We produce one cubic foot of unrecyclable solid waste per week (we don't compost) in a single closed plastic film bag that is perfectly suitable for use as a solid fuel for a commercial steam boiler that runs on such fuel to produce usable energy. We are fortunate that where I live there is an excellent recycling and hazardous waste disposal program which functions without heroic levels of government support and a well managed municipal landfill.

Ed Weldon

An interesting development in water filtration is the work of van Dinther et al. reported in J. Membrane Science 371:20-27 (2011) on the crossflow filtration of yeast. They were able to get high flux membrane separation by high crossflow velocity, with effective separation by filter pores 5x particle diameter.

Wilmot -- The trouble with these technical papers is that you have to be a member or pay a stiff fee to gain access to the text, etc. So perhaps you can elaborate.......

What types/sizes of particulates in potable water feedstocks are this paper's conclusions applicable to?

What level of water treatment volume would this technology be applicable to? Municipal water supply, portable single user drinking water treatment or somewhere in between?

Does the paper's finding suggest a simple implementation at a commercial scale or are there still questions about the scaleability of such a process?

Ed Weldon

Ed -- Mechanically assisted high flux microfiltration in a 300 gpm assembly, deployable in a truck, is the scale I was thinking. But I don't know much more than the scale would be deployable to manure ponds, coal ash ponds, mature fine tailings in the sludge ponds of Alberta, fruit and vegetable washwater. I don't know. It's still in the planning stage, but I'm moving along with it, and thanks for your interest.

Why this knowledge should disappear behind a paywall is a mystery to me, too, and a bad policy that needs to be looked into. But I paid. It is a short article, and the first paragraph of the conclusion concisely sums it up. I suppose it might be fair use to copy out the whole first paragraph here, but I will be ultra-cautious and only quote the first sentence of the first paragraph of the conclusion: "It was shown with well-defined metal microsieves, one can obtain retention of particles that are several times smaller than the pore size."

Mechanical assistance of membrane filtration can increase the effective pore size, making a microfilter into a nanofilter while keeping high flux. High shear means high shear lift (they call it inertial lift) effect to transport particles over the filter pore and into the stream going over the filter. That lift is enough to counter the skimming effect which would draw particles to the pore as flux is increased. There must be some swirl involved, so the pores turn into little vortex organizers for the smooth flow through the vortex cores through the filter. Like the Miller Lite vortex bottle for efficient chugging of beer.

In the experimental setup, van Dinther et al. produced high shear crossflow filtration by pumping a yeast slurry at ~1 m/s through a pipe lined with a 20 micron nickel microsieve. They found a high shear rate amplifies the effective filtration of a given membrane. So to sum up, in answer to your question: not limited in its application.

Rejecting particles much smaller than the pore size by means of the shear lift effect is what caught my eye in the abstract. And I believe the knowledge is worth far more than the $35 I was compelled to pay. But my optimistic view of high shear crossflow filtration in meeting these critical needs may be distorted by my personal interest: http://www.freepatentsonline.com/7757866.pdf