Disposing of cooling towers blowdown represents a key aspect of managing any cooling tower.
Cooling towers have become a staple of many industries: from chemical processing, to power generation. However, as current sustainability concerns and regulations are increasingly targeting water scarcity, blowdown water from cooling towers has been drawing more attention for its use of resources and polluting potential.
In this context, advanced solutions are emerging that allow operators to meet the challenges of cooling tower blowdown disposal while not compromising on results.
Today, effectively managing cooling tower blowdown involves a combination of advanced treatment technologies, optimized operational practices, and adherence to environmental regulations. Let’s take a look.
The importance of adequate disposal of cooling tower blowdown
The proper design of cooling tower blowdown disposal is a key aspect for several reasons:
Sustainability concerns
By design, water scarcity concerns are necessarily linked to any blowdown system for a cooling tower: blowdown involves the removal of a portion of the circulating water to prevent the buildup of impurities; to compensate for the lost liquid, new makeup water must be introduced, extending the use of water resources.
In this context, carefully designing a system that lowers blowdown stream is one of the key movements to achieve responsible water use in cooling towers.
Regulation compliance
Today, most cooling towers around the world are subject to regulation regarding their operations and, more specifically, targeting cooling tower blowdown. Many of these regulations don’t allow disposal via local sewage networks, and thus present the need to search and implement alternatives for operators.
Every cooling tower project is responsible for finding and complying with such regulations, which may be applicable both at a national and local level.
Avoiding equipment damage
To a great extent, the cooling tower’s efficiency and extended lifespan depend on ensuring adequate oversight of water circulation processes.
This includes cooling tower blowdown, crucial to guarantee the dissolved solids in the recirculated water don’t harm equipment via corrosion, scaling and other issues we delve into below in this article.
Cooling tower blowdown is key to target operational costs and use of resources
Because of the impact of cooling tower blowdown on water use and the system’s efficiency, designing an optimal system is crucial to cut costs related to resources, as well as those linked to disposing of blowdown.
Key challenges in disposing of cooling tower blowdown
High concentrations of dissolved solids
As water evaporates in the cooling tower, dissolved solids such as calcium, magnesium, chlorides, and silica become more concentrated. This results in a cooling tower blowdown containing high concentrations of dissolved solids.
The cycles of concentration (COC) tool is key to measure and understand this challenge. COC refers to the ratio of the dissolved solids in the cooling water compared to the makeup water. As a general rule, operating at high COC is desirable: it means cooling water is being recirculated multiple times before being discharged as blowdown. In other words, a high COC means water use is being optimized.
However, this demands an adequate monitoring and filtration system: if not properly managed, residues and impurities in recirculated water can lead to a number of issues including corrosion and scaling, as seen below.
Large volumes of wastewater
As seen above, regular blowdown is necessary to maintain the correct levels of dissolved solids. However, significant amounts of wastewater increase treatment and disposal costs. In other words, as the blowdown stream increases in size, disposal costs rise.
This aspect can represent a challenge and requires cooling tower operators to seek strategies to minimize blowdown volume.
Strict environmental regulations
Cooling tower blowdown is the target of environmental regulations due to its high salinity and the presence of chemical additives with polluting potential. As such, most regions have seen strict norms arise that regulate the discharge of cooling tower blowdown, so that impurities (chlorides, TDS, sulfates, organic content…) are removed before disposal is allowed. These emerge as a challenge as they require the design of alternative treatment and reuse solutions that comply with regulations.
Corrosion, scaling and fouling management
A number of problems can result from water recirculation that presents inadequate levels of dissolved solids. The main challenges in this scenario include:
- Corrosion: deterioration of the system’s metal components
- Scaling: precipitation of dissolved materials
- Fouling: it occurs when the dissolved solids in the recirculated water become concentrated and deposit on surfaces.
- Damage due to microbiological activity
Additionally, certain traditional treatment systems, such as brine concentrators, can suffer from corrosion problems, reducing their efficiency and increasing maintenance costs.
Proper management of these problems must be active, as they are capable of reducing the system’s capacities to operate efficiently and can cause serious damage.
Strategies to effectively address the challenges related to cooling tower blowdown
Implementation of recycling and reuse systems
Water recycling and reuse systems are essential to achieve water savings, so that cooling tower blowdown processes comply with regulations and generate operational cost savings.
The basic underlying principle for this strategy is to collect discharge water from one source and (after the necessary treatment), employ it as an alternative makeup water resource.
Today, advanced filtration and membrane technologies allow blowdown to be treated and reused, reducing freshwater consumption and minimizing wastewater discharge.
Successful examples of this strategy involve reusing condensation from air handlers, applying reverse osmosis to treat blowdown or using high-quality municipal wastewater (if available).
However, it’s essential to obtain expert advice on each project’s opportunities and applicable regulations in order to ensure the strategy is optimal for the cooling tower’s specifics.
Optimized water treatment
Optimized water treatment allows operators to face the challenges that arise from increased water recirculation, including potential corrosion and scaling. It is thus crucial for allowing cooling tower projects to operate at high cycles of concentration.
Today, solutions for water treatment are wide-ranging and have evolved at different paces. In order to meet each project’s needs, it’s essential to rely on expert advice that considers the specific needs and opportunities of the cooling tower at hand.
On the one hand, conventional chemical treatment programs are able to manage corrosion and scaling, as well as ensuring optimal cycles of concentration, through a variety of methods, such as:
- Corrosion inhibitors
- Scale inhibitors
- Biological fouling inhibitors (biocides)
- Dispersants
As such, proper use of scale inhibitors and pH management can minimize scaling and corrosion, reducing the frequency and volume of necessary blowdowns.
Additionally, new approaches to water treatment have emerged to provide alternatives to or complement traditional treatment options. These include:
- Water modeling software: involved in modelling the system’s corrosion and scaling trends and suggest optimal chemical treatments, all while taking into account the project’s specifics regarding water composition and other variables.
- Automated treatment systems: working hand in hand with the modelling platforms, a number of technologies have emerged to allow automated control of cooling tower blowdown as well as other aspects such as pH control, based on real-time data.
- Other alternatives: green chemistry programs or chemical-free models (such as those based on ozone or ultraviolet biocides) aim at further helping companies comply with environmental regulations by reducing treatment byproducts that are potentially problematic.
All in all, these solutions’ goal is to limit blowdown stream by ensuring water recirculation is done without compromising the equipment’s longevity and efficiency.
Adoption of Zero Liquid Discharge (ZLD) technologies
The aim of this model is to completely eliminate liquid effluents, reducing the environmental pollution related to blowdown processes. In order to do so, ZLD is designed to recover as much water as possible from the process, while also converting waste into solid residue.
This strategy addresses challenges related to strict environmental regulations and promotes a more responsible and efficient use of water as a resource.
Industries such as power plants, textiles, pharmaceuticals, and chemical manufacturing have already applied ZLD successfully, thus promoting water reuse and complying with environmental regulations.
Today, a number of different approaches to ZLD are being experimented with in order to achieve this result. One example involves the combined use of microfiltration (MF), ultrafiltration (UF) and reverse osmosis (RO) to blowdown water from cooling towers.
In this pressure-based membrane system, these three processes allow for the removal of both suspended solids, dissolved solids and bacteria before demineralization, all by pushing water through different membranes. This method has shown significant opportunities to improve the system’s efficiency by removing problems related to corrosion in brine concentrators, as well as reducing their energy load.
All in all, new models related to cooling tower blowdown can put water savings at the forefront while also incurring in less operational costs and an overall improvement in the systems’ efficiency and longevity.
Critical to achieving these goals is relying on the right partner, offering professional advice related to water treatment options that prioritise optimal water efficiency and high cycles of concentration.
As seen above, optimal design of cooling tower blowdown processes is challenging per se. This process can be further complicated when considering the specifics of each project: from local regulations to the characteristics of the available makeup water.
This is where ARANER comes in. We put our thermal engineering expertise at the service of cutting-edge developments where efficiency and sustainability are critical.
Committed to design and implement cooling tower solutions where energy savings and reduced water consumption are priorities, we focus on allowing for extended equipment life and compliance with environmental requirements.
Want to learn more? Discover our district cooling line and get in touch with us to talk to our team of experts about how we can help you.
LINKEDIN
YOUTUBE