It is a rare and delightful occurrence when altruistic motives and the quest for profit coincide in such a way that following one begets the other. The reuse and recycling of waste water is just such a project, especially in industrial applications replacing municipal potable drinking water supplies. When one considers the fact that more than a billion people in the world are without adequate drinking water, the altruistic reasons for conserving usable water becomes readily clear. Thankfully, a point has been reached where the concept to conserve on water by reuse and recycling has become easy and cost effective to implement as well, providing an opportunity to solve this problem in an efficient manner.
When considering the methods to conserve on water, it is important to remember that the capstone goal of this process is a reduction in the amount of water drawn out of an aquifer; the reserve of clean water that is underground, and the source of most water consumed in the United States. Any reduction of this input in the form to conserve on water through water reuse and recycling, the use of alternative sources and even simple steps to conserve on water furthers this goal, with the added incentive of saving the one dollar average cost of municipal potable drinking water per thousand gallons ($1.00/1,000 gallons) in the United States.
It is possible for an industry to reduce this dependency on municipal potable drinking water in a few ways. Perhaps the most intuitive of these is the capturing and use of rainwater instead of municipal potable drinking water, which can be very useful in places that get enough rain to make the requisite infrastructure cost-effective. When the supply is reasonable, this is a very effective and easy to implement source of clean water for industrial processing or sanitation procedures, as well as any water use tasks which are not regulated by the U. S. Food and Drug Administration.
A potential abundant source of water for industrial uses is grey water from either an industrial or non-industrial domestic source. Grey water is all domestic waste water except toilet discharge water. This can be water from sinks, bathtubs and clothes washers in a domestic setting, or from floor-washing and equipment cleaning in an industrial setting. The benefits of grey water use are twofold: First, the supply is usually more consistent than rainwater in many climates, which increases the predictability of the economic incentive to use this water source. Second and more importantly, grey water requires very little processing to be used in certain applications, many of which are responsible for the production of this grey water in the first place. Water that has been used to wash hands or clothes may require only minimal treatment to be usable for the cleaning of floors or the irrigation of landscaping in a non-industrial setting, or for cooling and cleaning in an industry.
Treated wastewater is another plentiful source of water which has similar usage restrictions as grey water or lightly processed rainwater. This is an abundant source of water aside from municipal potable drinking water supplies or individual wells. The use of treated effluent, with some quality management controls, can be suitable for a wide range of uses. These include toilet flushing and especially crop or landscape irrigation.
While a primary environmental incentive to conserve on water is driven by the cost of industrial input, a primary economic incentive to reuse and recycle water in an industrial setting is a reduction of municipal sewer discharge. While municipal potable drinking water can cost about $1.00 per 1,000 gallons, the price to return or discharge the waste water back into a municipal sewer system is likely as much as 500% or five times that amount ($5.00/1,000 gallons). Usually recycling water will also reduce dependence on municipal potable drinking water sources, and there are many ways that it is possible to reduce the amount of water discharged into a municipal sewer through effective reuse and recycling to conserve on water.
Because one of the most important barriers of beginning a project to conserve on water is initial cost, it is important to consider inexpensive solutions as much as expensive ones. It is here that a focus on the specific water uses is most effective. These solutions can tend to be slightly smaller in scale, but substantially cheaper than larger scale reclamation efforts to implement. For instance, it is possible to reuse water for cooling, either in evaporative cooling machines or simply to transfer heat to cooling towers. If water for these is taken from water-using industrial processes or grey water sources, it does not have to be discharged into a municipal sewer. This type of use saves money, and it often reduces reliance on municipal potable drinking water by taking the place of water sourced from municipalities, only to be used for cooling. Opportunities for water reuse such as these are common.
In some industries, one of the most prolific uses of water is cleaning as the industry sanitizes. Sanitation is often a less considered point where industry can apply procedures to conserve on water, because it usually requires several separate simple steps. Fortunately these simple steps are often small and incredibly cost-efficient. While using recycled water can be very useful for cleaning, it is also possible to conserve on water simply by changing hose nozzles to low-flow, high-pressure nozzles which decrease the amount of water output per minute. It is also possible in some applications to use a squeegee during cleaning instead of water, which can further reduce water use. Though these savings may seem small, in some cases the amount of water used in sanitation can equal or exceed that used in actual industrial production, providing an ideal opportunity to conserve on water and an impressive, cost effective increase in profit.
While residential water users can find economic advantage in water reuse systems, it is industrial processes that see a large opportunity for economic benefit. The significant challenge in implementation is that every case is unique. The source process must be considered to determine what impurities are contained in the water, and the process that will use the water next must be considered in order to determine which of these impurities must be removed. Processes with physical solids such as fats, oils and grease discharge water require different processing than those with dissolved solids. However, the benefits of these steps often dramatically outweigh the costs, both because of the economic incentive to decrease input water and output use, and because this processing ensures internal quality control.
The industrial applications of reclaimed water are practically limitless given the variety of industry uses for water. Properly treated waste water can often be reused and recycled in the same process that created the waste water in the first place. While these varieties of treatment techniques are often the most expensive, they also provide the most striking reduction in water use and disposal costs, as a very large percentage of process water can be reclaimed thru recycling and reusing instead of discharged into municipal sewer systems.
When water recycling is simple, it often needs very little treatment. However, when more intensive treatment is required, an industry procedure can include ultra-filtration and reverse osmosis. Both of these processes are designed to remove solids from water by passing it through a semi-permeable membrane. The difference between these processes is that, in ultra-filtration, physical solids (known as Total Suspended Solids) are primarily captured by the filter and discarded/rejected having an effluent virtually free of these physical solids known as UF Permeate. With reverse osmosis, the UF Permeate water, which can be the source water for the Reverse Osmosis Unit, is pushed through the membrane at high pressure, leaving the source side/RO reject containing an increased concentration of dissolved solutes while having purified water as its effluent referred as RO Permeate. In some cases where industry uses expensive solutes, such as chemical plating lines, this can supply an increased opportunity for solute reclamation.
In order to illustrate various applications in which waste water treatment can prove effective; I will explain a pair of my concrete hands on examples. I have consulted one specific food processer continuously more than fourteen year’s. After purchasing municipal potable drinking water, this plant used the water in their process and then discharged 740,000 gallons per day of treated wastewater to the municipal sewer. The local receiving regulatory sewer authority documented consistent daily waste water discharge volumes to have been over the allotted municipal sewer permit. In order to bring this plant’s waste water discharges volume into compliance with their municipal sewer regulatory authority discharge permit, I oversaw a number of process modifications. Change in sanitation procedures were implemented with the goal of decreasing water use, as well as alterations to industrial processes. One of the largest water use savings was a revision to the plant’s twelve large vacuum pumps cooling water discharge. Each of these twelve vacuum pumps used an approximate average of 8,000 gallons per day of purchased municipal potable drinking water for cooling, which gravity flowed straight into wastewater for treatment and then discharged into the municipal sewer. We changed this process to redirect the vacuum pump cooling water discharge by pumping through the plant’s cooling towers and recycle the water back to all of the vacuum pumps for their cooling. This didn’t require any sort of additional filtration, it was simply a process modification; a modification which saved an accumulated volume of approximately 100,000 gallons of water per day for purchase, treatment and discharge. The aggregate of all of the facilities alterations is that this food processor now discharges an average of less than 600,000 gallons of waste water per day to the municipal sewer after purchase and use. This is a 20% water decrease which was brought about through a few simple process revisions, from the alterations in the pumping system to a shift to low-flow hose nozzles and the use of squeegees for cleaning tasks (Fig. 1).
An excellent example of a more complex industrial reclamation comes from a plastic recycling wash line facility’s waste water treatment plant where I led my consulting customer’s project (Fig. 2). The information for this system indicates the cyclical nature of industrial filtration. A professionally arranged system is designed to purify two-thirds of water volume to be available for reuse; results from my project follow. At this 24/7 facility, the incoming untreated waste water was 75 gallons per minute (gpm). Waste water was processed through both (Fig. 3) ultra-filtration (UF) and (Fig. 4) reverse osmosis (RO) units. The RO effluent purified water volume is of particular interest because it amounted to approximately two-thirds of the untreated water volume to approximately 49.2 gpm, processed with the quality that the United States-Food and Drug Administration (US-FDA) recognized its purity adequate to replace purchased municipal potable drinking water. Finally, the amount of waste water discharged into municipal sewer approximated 19.7 gpm. This meant that of the 75 gpm untreated waste, the combined UF and RO unit processes discharged only 19.7 gpm treated wastewater into the municipal sewer system. When this entire system is considered, the end result is 49.2 gallons per minute are reclaimed/reused purified water by this operation. This equates to a truly awe-inspiring savings of more than 70,000 gallons of water per day that does not need to be purchased. Instead of discharging 108,000 gallons per day of treated waste water into the municipal sewer and paying for all of its associated costs, the plant only discharges a little more than 28,000 gallons per day. This registers nearly a 75% decrease in overall water costs.
These two examples describe the extraordinary savings that can be accumulated through the careful execution of water/waste water management. Unfortunately, as with many projects to conserve on water, there may be staggering expenditures of up front infrastructure, which could be cost-prohibitive in many applications. Additionally, ultra-filtration and reverse osmosis processes can be overwhelming to implement on a very small scale. An ideal solution for many small industries could be a centralized water purification plant within an industrial park, where all participants have purified water available as a replacement of municipal potable drinking water in an efficient manner, assisted by the economy of scale that such a larger centralized water purification plant would provide.
Despite the economic barriers to more intensive wastewater reclamation procedures, all industries can profit from a thorough examination of their water use. Economic pressures will always favor efficiency and cost saving measures such as water reuse and recycling, whether this means a large industrial processing plant or a more simple solution, such as changing hose nozzles and perhaps collecting rainwater. Thus, there is significant incentive to conserve on water and preserve our limited water resources. Industry focuses on economic incentives by necessity and with good reason, but we as citizens of the world must also take into account the environmental benefits. Access to clean drinking water is something that everyone, person or industry, can help ensure. We must always remember that not all solutions have to be very large or very costly in order to be very effective. Instead, it is the process of incremental change which underlies our growth. The relatively simple solution of altering the cooling of vacuum pumps to recirculate water can save enough capital to allow for other, more costly but even more effective steps to reuse and recycle waste water that would otherwise be discarded as economically unfeasible. Begin now. Save money, and be a good shepherd of the environment at the same time. Opportunities as clearly good as this don’t come around too often.
About my bio; Daniel L. Theobald of Environmental Services:
I am the proprietor of Environmental Services. As a professional Wastewater and Safety Consultant/Trainer; I am known in the industry as “Wastewater Dan”, have more than 24 years of hands on experience in the industry operating many variants of wastewater treatment processing units, a trainer in Wastewater & Industrial Health & Safety topics and eager to share with others to conserve on water (www.ConserveOnWater.com). I serve as an active consultant to a variety of industries, achieving and maintaining consistent improved wastewater treatment at reduced cost. I am a Lifetime Member of the “Who’s Who Registry of Professionals.” I hold numerous certifications from several wastewater management regulatory boards and professional organizations. I am currently the primary author of one chapter revising the Water Environment Federation’s (www.wef.org) Manual of Practice # 29 (MOP-29); a Technical Manual resource guide for Biological Nutrient Removal. This revision for Wastewater Operators is scheduled for publication in 2013. I also author an industry-related blog (http://TheWastewaterWizardBlog.com/).