Ensuring process water clean-up and compliance

Water quality is vital throughout this process to prevent product contamination and equipment damage, but particularly to minimise any potential harm to ecosystems once it is released. To achieve this, and enable water to be reused within the industry or elsewhere, it must be meticulously treated and decontaminated before being discharged.

Regulations are in place to control both the quality of discharged water and the quality of water during the treatment process. To enable the industry to meet these regulatory requirements, process water treatment must be supported by reliable and accurate analytical techniques.

Key aspects of water clean-up compliance

Analytical technologies are required to ensure the industry meets stringent regulatory limits. Within the industry, it can be difficult to adhere to strict requirements, such as those of the Environmental Protection Agency (EPA). In part, this may be due to the way regulations evolve; often, regulatory bodies work closely with instrumentation companies. Other times, however, limits may be dictated by research that has revealed detrimental impacts on aquatic, animal, or human health – and the imposed requirements might stretch analytical instruments to their limits.

Technologies used to enable process water treatment can be divided into two categories: clean-up and analytical. Clean-up technologies handle the removal of damaging biological or chemical contaminants, e.g., nutrient treatments that remove or eliminate ammonia, or biological treatments that remove dissolved organic matter. Analytical technologies, on the other hand, ensure the removal process has been successful. They are typically online instruments that ensure contaminant levels have been reduced enough to satisfy relevant regulatory requirements and enable continuous monitoring of compliance.

Technologies for water testing: types and considerations

Process water analysis is supported by both electrode-based and optical (reagent-based, colorimetric) instruments, which suit different types of regulations. Typically, discharge permits come with upper concentration limits specific to certain contaminants, and are best supported by colorimetric, reagent-based technologies. In other cases, permits may specify a maximum acceptable level of turbidity to help with the identification of bacterial or algal blooms, for example. In this case, a less specific optical method may be used to assess turbidity. Together with electrode-based methods, these technologies are incredibly important for protecting marine life as they ensure the removal of harmful products such as chlorine-based disinfectants.

When it comes to the measurement of contaminants, technologies must be applied across several key stages of wastewater treatment: filtration, biological treatment, disinfection, and the removal of disinfectant residual. To confirm adequate contaminant removal, online technologies are applied, typically using electrode-based and optical water testing. These technologies are the most suited to helping companies meet regulatory requirements and are also the most cost-effective options. UV-based analysis technologies are also gaining acceptance by regulatory bodies, and are therefore increasingly used for monitoring. Several key factors guide the selection of technologies for process water analysis; one of the most important is the level of sensitivity required, i.e., the lowest concentration of contaminant that needs to be detected. Largely, this will be influenced by the stage of the process. At the early stage of water intake, contaminants only need to be identified – but accurate quantification is less important. Although the need for sensitivity is lower, the water intake stage has its own challenges, as high concentrations of non-target contaminants can interfere with measurements. During process treatment and discharge, accurate quantification is required to confirm contaminants have been removed. Depending on the specific contaminants that need to be detected and quantified, and based on the relevant regulatory requirements, more or less sensitive technologies may be needed; for example, residual chlorine contaminants need to be detected in parts per billion.

Sample quality is another important deciding factor as electrode and optical-based methods are suited to different conditions. Dirty, inadequately treated samples should be analysed using technologies that provide robust measurements despite the high level of contaminants and particulates. Due to the nature of optical analysers, highly turbid samples are problematic; while contaminants do not typically damage optical sensors, their presence is a major source of interference. Fortunately, advanced pre-filtration technologies and robust reagent formulations have improved this significantly. Electrode-based technologies, on the other hand, are less affected by turbidity, but can be more susceptible to dissolved interferences and biofilms. Therefore, electrode-based technologies have historically been used for cleaner water samples. As with optical analysers, supportive technologies for electrode-based methods have also improved greatly in recent years; long-term deployment of electrode-based methods has been made possible by wipers or polytetrafluoroethylene (PTFE) beads that continuously clean the sensor.

Of course, all factors must be balanced against economic consequences. Electrode-based sensors are widely seen as highly economic due to lower running and maintenance costs than their optical counterparts.

Fulfilling the industry’s environmental responsibility

In addition to meeting regulatory requirements, the hydrocarbon engineering industry also has a huge social responsibility to ensure processed water is treated appropriately before being returned to the environment. This can be achieved through water treatment and online analyses, which enable contaminant removal in line with relevant regulatory requirements. Electrode-based and optical testing technologies are the most common approaches to water analysis, and are each suited to different stages of the treatment process. Overall, considering the process stage and opportunities for implementing robustness are critical to ensuring analytical success and, ultimately, enabling the industry to meet its sustainability objectives.

Written by Chris Searle, Process Water Analysis Specialist, Thermo Fisher Scientific.

Chris Searle is a Process Water Analysis Specialist for Thermo Fisher Scientific. He is committed to helping customers find the best solutions for their process monitoring needs. Chris has 10 years of global commercial, technical and product management experience, using his technical knowledge to facilitate deployment of laboratory-grade techniques in the toughest environments. With a master’s degree in Chemistry from the University of Reading in the UK, Chris has noted expertise in electrochemical trace metal analysis, in addition to several years of experience with electrochemical and spectroscopic instruments for field and on-line deployment.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/05082021/ensuring-process-water-clean-up-and-compliance/