Water treatment is a critical issue at many chemical plants because process, cooling and makeup water play important roles in operations. Poor water treatment chemistry usually induces corrosion, scaling or fouling of equipment and systems that, in turn, can cause equipment failure and sometimes even plant shutdown. Such incidents may incur enormous costs and, even more importantly, may jeopardize employee safety. Yet, time after time, we’ve observed requests for proposals (RFPs) for water treatment programs that are noticeably incomplete or based on outmoded ideas. So, here, we’ll provide an overview of important items that should be in an RFP to allow the water treatment vendor to select the correct program(s).
At existing plants, RFPs for modification or change to water treatment programs may arise for a variety of reasons, including performance concerns, service issues, reaching the mandatory time period for a rebid, procurement initiatives or cost evaluation. The driver for the RFP will greatly influence the effort required by the vendor in preparing a bid, and may lead some suppliers to give minimal attention or not bid the project at all if they don’t see a benefit. This underscores the need for clear communication to achieve the best results from the bid process.
Do The RFP Right
Very commonly for both existing and new projects, suppliers receive an RFP with scant data regarding the actual technical details of the project. Indeed, there have been cases where a large RFP mainly consists of front-end legal descriptions with insufficient technical detail. So, let’s look at some deficiencies that afflict RFPs and the bid process, and outline some necessary information for a proper evaluation.
Water quality data. Comprehensive chemistry data for makeup, cooling and process water are extremely critical for determining proper chemistry programs and also for selecting equipment type and size, especially at new plants. Often, however, RFPs will arrive with just partial chemistry data, sometimes only from a single analysis. Worse still, we’ve encountered RFPs and design engineers who simply say, “Design to standard water.” The only thing standard about water is that it’s wet. Analyses should show any trends in water quality over time and contain a full list of major cations and anions, along with minor elements/compounds, including metals, organic carbon, pH, suspended solids, nitrogen-based species and others. For makeup water, its source obviously will significantly impact the quality and impurities that need treatment. Increasingly, new plant designs are moving away from fresh water supplies. Municipally treated wastewater (reclaim water) is becoming a popular alternative; compared to fresh waters, it typically contains markedly higher concentrations of ammonia, nitrites/nitrates, organics, phosphorus and suspended solids, which, if not treated, can cause serious problems in cooling systems and other locations.
Process water quality data, including readings from the steam generators and condensate return, where applicable, also are important. Impurities can enter these streams from many sources. For example, heat exchangers that operate with process fluid at a higher pressure than the steam heating supply may introduce a variety of contaminants to condensate. Turbine exhaust steam condensers are a common location of impurity ingress; they typically contain thousands of tubes (Figure 1) and even a single tube failure allows cooling water to enter the condensate.
Continuous online monitoring of condensate and boiler water chemistry is an absolute must to prevent serious to potentially catastrophic damage in steam generators.
Up-to-date plant water balance. Every new plant invariably has a water balance to outline process flows throughout the facility. However, these flows often change considerably over the life of the plant as new equipment and processes are added and others retired. An accurate up-to-date water balance is critical for evaluating and modifying treatment programs. Frequently, establishing current flow volumes requires ultrasonic flow measurement. A problem that plagues many plants, apart from the water balance, is location of underground piping, regardless of whether the pipes contain water or other fluids. Too often, plant personnel must rely on the memory of long-time employees because installation of additional underground piping was never properly documented.