These days, the importance of a fresh water supply and safely-treated wastewater return to the river cannot be overemphasized. No matter how hard we try, we are still a long way from the most efficient, economic and reliable ways to ensure that our cities are properly equipped and ready for the clean water challenge.
As a civilization, we have achieved isolated instances of superb efficiency in water treatment and reuse, such as space shuttles and stations that rely on the almost perfect use and transformation of the precious water cycle, as there is no alternative other than that, in space. But on the ground, the quantity of issues are grander and not as technically advanced. Yet this is where are our world is and what we have to work with—a world in which we must be in tune with nature and our environment as we look toward more innovative ways to maintain a fresh water supply and safely treat wastewater.
Chemical vs Biological Treatment Methods
Is wastewater about to be treated in other more innovative ways? Currently, most plants use a combination of biological and chemical waste stabilization. Increasingly, EPA is presenting the idea of making wastewater effluents cleaner in terms of nutrients. This forces more plants to add large quantities of chemicals to polish their effluents. The other unintended effect is that multiple systems now need more maintenance. Wastewater plant operators have trouble maintaining complicated systems while keeping costs low. Eventually, chemical stabilization methods will displace some of the biological stabilization techniques.For instance, one big problem area is biological phosphorus removal followed by anaerobic digestion. The unfortunate consequence of this procedure is the release of phosphorus back into the plant, whereas chemical phosphorus removal permanently ties up the phosphorus until it leaves the system.. Complex systems are not only hard to run, they are expensive to maintain.
Protecting treatment pumps (primary, secondary and tertiary) from grit that accompanies the incoming water is an important component of extending equipment life. The ways that water is pumped have undergone changes, as well. The traditional end suction pumps have steadily been replaced by wet submersible units and now even by dry submersibles, which are mounted into a dry pit and connected to a wet pit allowing easy access to the pumps for repair or maintenance.
Combined sewers present challenges, and separating the water streams is expensive. In practice, the more readily accessible piping is handled first, and the more difficult accesses are put on hold until later. With the complexities involved in sewer separations and the disruptions to business, many communities are turning to tunnel collection systems when upgrading (due to capacity issues or government regulation) is required. Increasingly, deep drop shafts have become common in many urban areas. The drainage of storm water will be benefited by the implementation of drop shafts.
Simplified Repairs and New Materials
Repairs must become simpler and faster. Presently, maintenance departments conduct simple repairs in house, and large and more sophisticated equipment is repaired by outside contractors. Systems are more complex, and more computers are used to control them. Computer specialists, who have good technical understanding of the systems, are more common at wastewater treatment plants, but they may lack the knowledge of working on the equipment. Likewise, maintenance personnel may be experienced with the equipment, but may lack the technical knowledge of the systems. A disconnect between the equipment handling and the systems that operate and control the handling can occur. More training is required to bridge this gap. In addition, more interactions between the departments and groups are essential .
New materials are available today that were novel or nonexistent years ago. For example, duplex stainless steel performs better in high-G centrifuge applications. Composites are becoming more common, bringing with them the advantages of light weight, cavitation resistance and corrosion resistance.
How will our plants look 20 years from now? Hopefully, higher efficiencies and effectiveness of systems will mean less waste and a better recycling of resources. We may see technologies applied and new trends. Perhaps water and waste treatment plants will combine, and less wastewater will be discharged into rivers, and more of it participating in a closed cycle, making our rivers safer and more environmentally friendly.
Plant space (or green areas), particularly in cities, will have to be used better, and some communities will likely apply new methods—such as closed-cycle water systems y—to be more self-sustaining and less polluting. Remember the experiment with biosphere, conducted in Arizona years ago? This type process can work in a small-scale situation. The challenge is to implement it on a wider scale.
The benefits of closed-water systems would be impressive. Less water discharged to rivers would mean less piping, less repairs and less groundwork disruptions, and and easier-to-preserve infrastructure. Problems that are common today—such as cracked pipes, infiltration and plugging—would go away.
Sunlight energy could be better used, with solar panels and special bacteria growing methods that may advance us even further, making us less energy dependent and more efficient.
Perhaps one day, present issues with our water supply will be reversed with more innovative water treatment and delivery systems. The public is increasingly concerned if we actually remove all the harmful pathogens in drinking water in urban areas,.
Sunlight energy would be used better, with solar panels, and special bacteria growing methods will advance even further, to make us less energy dependent, and more efficient.
It is difficult to tell, how the world will look in 20 years. However, if we do not try to imagine it today, we may find ourselves unprepared in the future. Perhaps the time to plan or at least talk about it, is now. We would like to hear input from our readers,, and we welcome any additional ideas, challenges or thoughts that you may have.
Pumps & Systems, September 2010
Dr. Nelik (aka "Dr. Pump") is president of Pumping Machinery, LLC, an Atlanta-based firm specializing in pump consulting, training, equipment troubleshooting and pump repairs. Dr. Nelik has 30 years experience in pumps and pumping equipment.
Chris Staud, Engineering, Wastewater Group, Atlanta, Ga.