By Jose Maria Gonzalez
Regulators in Colombia are strengthening the standards and enforcement of water treatment processes aimed at protecting public health from microbial contamination and chlorine-resistant pathogens, such as Giardia and Cryptosporidium. The regulation comes as population growth and inadequate treatment of municipal and industrial wastewater continue to negatively impact the quality of the country’s source-water resources.
Rather than expanding conventional filtration or chemical treatment systems, a private water utility in Colombia is turning to ultraviolet disinfection as a faster, simpler and more cost-effective way to improve water quality and comply with new regulations. In December 2015, Progresar E.S.P. commissioned its first UV system to provide additional disinfection at the 10-year-old Teusacá River Treatment Plant that serves about 5,000 residents in a suburb of Bogotá. Plant operators (see Figure 1) were fully trained by the UV manufacturer to operate and maintain the UV systems at the plant. (The team also supports an additional plant and 105-km pipe network. )
UV provides means to enhance treated water quality
UV technology provides many benefits for this facility, which draws water from the Teusacá River. A tributary to the heavily polluted Bogotá River, this rural waterway is negatively impacted by microbial contamination from agricultural runoff and treated effluent discharged from upstream wastewater facilities.
“UV disinfection brings the ideal combination of performance, ease of use and design flexibility to upgrade the water treatment processes for this plant,” says J. Enrique Baena, General Manager, Progresar E.S.P. “We are very proud to be the first in Colombia to adopt a reflective, dual-lamp UV technology in our treatment plant and lead the way in supporting stronger regulations to protect public health from waterborne pathogens.”
The utility has installed 10 such units at the plant, each one capable of providing disinfection for up to 30 gpm (1.9 L/sec) of water (see Figure 2). The use of multiple UV systems makes the plant inherently more reliable and energy efficient than those using a conventional approach, which typically operates with a large, single-reactor system. During peak demand, the units can work together to achieve treatment requirements; during low demand, individual units can be shut down to conserve energy and extend the life of UV lamps. This design also enables operators to conduct repairs or maintenance to individual UV systems, without decommissioning the entire UV disinfection process.
The Teusacá River Treatment Plant operates at an average flow of about 190 gpm (12 L/sec) and can achieve a peak flow of about 300 gpm (20 L/sec). The plant is equipped with a multi-barrier, conventional treatment system designed to handle the highly variable river water and also provide robust pretreatment for the UV systems. As raw water enters the plant, it is first treated by aeration through a cascade system, flocculation, sedimentation and filtration. These processes produce consistently high-quality feedwater that meets the specifications for the UV systems. The systems, however, are also designed to perform under difficult conditions and can achieve effective disinfection even when ultraviolet transmittance (UVT) is as low as 75 percent. This provides a major advantage for the plant, especially when dealing with surges in organic material and bacteria that the pretreatment system may not be able to adequately remove.
After passing through the UV systems, chlorine is added to prevent microbial contamination in the distribution system and to comply with the local regulations for chlorine residual. “Since the UV systems have been operating, our chlorine use has declined to about 50 percent of what we used in the past at this plant,” Baena says. Not only does this contribute to operational savings, but may also help reduce the formation of DBPs such as trihalomethanes, which form when chlorine reacts with organic particles in the treated water.
Plant achieves zero-percent Water Quality Risk Index
“Our UV systems are performing very well and are enabling the plant to consistently meet the treatment requirements and achieve a score of zero percent for the Water Quality Risk Index,” Baena says. This method of risk analysis was established in 2007 by the Colombian government to assess risk to human health from potable water. It is calculated using several parameters including the physical, chemical and microbial characteristics of the water. When it comes to risk, zero is the best score and indicates the highest-quality water (see Figure 3).
The performance of the UV systems can be attributed to their unique design. Each system incorporates two proprietary high-output UV lamps that are mounted in air rather than in the quartz sleeve. Elliptical reflectors encircle the lamps and help to reuse the energy and deliver a UV dose that is 2.4 times greater than that of conventional systems. This high UV dose enables the systems to provide effective disinfection at the maximum flowrate, even when the UVT is as low as 75 percent. Reflecting the UV light also targets pathogens from 360 degrees and eliminates the risk of shadowing, which is more likely in conventional systems and could allow live pathogens to pass through. As a result, the treatment plant is consistently producing potable water that is completely free of total coliforms, E. coli and P. aeruginosa.
Dual sensors instantly diagnose alarms
Each system also incorporates smart controls and dual UV sensors that continually monitor three critical performance parameters: UV dose, UV lamp intensity and UVT. Like the lamps, the sensors are also mounted in air, which eliminates fouling and makes them easy to access by operators (see Figure 4). Data from the sensors enables the system to instantly diagnose an alarm and determine if it is caused by an issue with the lamp or by poor water quality. Each UV system is connected to the plant’s central control panel, so once an alarm is triggered, an operator can be notified to address the issue.
Other UV systems use single-sensor designs that are unable to diagnose alarms and require operators to perform time-consuming troubleshooting procedures before they can address the issue. These single sensors are also often mounted inside the UV chamber in contact with the water, which exposes them to contaminants, causes them to foul and leads to false alarms if not properly maintained. Simple maintenance and automated controls could be key factors to help the nation meet its goals for improved water supplies throughout the country. According to a document by the Canadian Trade Commissioner, the Colombia government has set a goal to provide improved water sources and basic sanitation to 100 percent of urban areas and 80 percent or rural areas by 2019.
Decentralized, automated treatment facilities will likely be the solution of choice to provide cost-effective delivery of clean, safe water in rural areas. The UV systems at Teusacá River Treatment Plant are demonstrating that they are certainly up to the task. In other parts of the world, many of these UV systems operate for years without any need for cleaning of the quartz sleeve by the operator, because each system is equipped with a robust, mechanical cleaning system that prevents fouling and ensures maximum light intensity. The systems are connected to an uninterruptible power supply, to ensure continued operation, especially in rural areas where the electrical supply is not reliable (see Figure 5). A power conditioner can also be added to sensitive components from damage caused by over- or under-voltage conditions.
Scalable design accommodates community growth
In the coming years, the community is anticipating a surge in population that will see more than 12,000 people tapping into the water treatment plant. Progresar E.S.P. is prepared for this growth and can easily expand treatment capacity of the UV system by adding more units. Multiple manifold systems can be joined together to achieve flows of up to one MGD (44 L/sec). The UV manufacturer has developed strong relationships with Progresar, as well as a local distributor that manufactures the interconnecting manifold system and provides service and support for the UV units throughout Colombia. The success of this project demonstrates that the team and the technology can provide a cost-effective, easy-to-operate solution to help Colombia meet its objectives for clean, safe water throughout the country.
About the author
Jose Maria Gonzalez is the Director of Sales, Engineered Solutions for UV Pure Technologies where he is responsible for developing business opportunities and distribution networks in Latin America, the United Kingdom, Australia, New Zealand and Southern Ontario, Canada. He brings more than 20 years of experience as a consultant and entrepreneur for a number of environmentally focused technology companies, including solar energy, biogas and biomass feed stocks. Prior to UV Pure Technologies, Gonzalez was the VP of Business Development for Clearford Water, where he played a key role in the selection of the Clearford One™ system for a wastewater treatment and reuse project in Colombia. He holds a degree in chemical engineering from Universidad Pontificia Bolivariana in Colombia.
About the product
UV Pure Upstream 30-75 disinfection systems, with patented Crossfire Technology®, are engineered to meet the Class A requirements of NSF/ANSI Standard 55 (but are not NSF/ANSI 55 Class A-certified where regulations do not require it). Field-tested and proven with over a decade of demanding municipal, industrial and commercial applications, Upstream Systems are for potable, reuse and rainwater applications and are effective even on surface water from lakes, streams, cisterns and dug wells.