Getting Ready for Chemical Interruptions at WRRFs

Introduction: The water and wastewater industry is facing new challenges in the chemical supply chain due to recent pandemic conditions, hurricanes, and wildfires. As a result, Water Resource Recovery Facilities (WRRFs) are looking ways to improve the chemical resiliency of their facilities during chemical shortages, emergencies, or any disruption in chemical supply chain. The main objective of this paper is to assess the risk from chemical shortages, and present strategies to WRRF's to mitigate risk through consequence and vulnerability reduction. Background: Recently, Hazen has teamed with Orange County Sanitation District (OCSan) to conduct the Chemical Resilience Study for their Plant 1 and Plant 2. The approach to quantitatively assessing and managing risk is based on the ANSI/AWWA J100 Standard: Risk and Resilience Management of Water and Wastewater Systems. The J100 standard provides the framework for assessing baseline conditions as well as improvements following the implementation of risk mitigation. Risk is defined as follows: RISK = Consequence X Vulnerability X Likelihood Table 1 summarizes the approach to reduce consequence and vulnerability for OCSan. This approach will allow to assess baseline risk for WRRFS, as well as provides clear path to reduce the risk, either by reducing the consequences of supply disruption or improving system resilience (i.e., reducing vulnerability). Table 1: Approach Adopted to Reduce Risk for OCSan Methodology: The following methodology was developed to reduce the risk of WRRFs to chemical shortages and disruptions - Chemical Risk Analysis: Estimating the likelihood of chemical shortage requires understanding the chemical supply chain and availability of substitutes. Industry trade groups and chemical suppliers were contacted to understand manufacturing locations and the sources of raw materials. - Vendor Alternatives. Alternative vendors were identified using information from industry trade groups, as well as reviewing chemical bids from OCSan and similar utilities. The use of chemicals in other industries which might be supplied by alternate vendors was also reviewed. - Delivery Alternatives. Alternative forms of deliveries including bulk liquid, totes, and dry chemical delivery with onsite dilution were also investigated - Chemical Alternatives. Alternative chemicals were identified to existing chemicals Findings The chemicals evaluated in OC San Chemical Resilience Study are grouped under four main categories and listed in Table 2. These chemicals are used in the following plant process areas: preliminary treatment, primary treatment, secondary treatment, odor control, effluent disposal, solids handling, and power generation. Table 2: Chemicals Evaluated at OCSan Chemical Resilience Study Chemical interruption to facilities could result from the following conditions: - Lack of delivery access due to a natural disaster - Interruptions from manufacturers and/or vendors - Chemical shortages - Increased cost of chemicals - Increased demand in other industries - Delays in deliveries - Regulatory changes Evaluation of the baseline conditions for OCSan's chemicals identified that most chemicals used have over two weeks of storage available in the event of interruption. The only chemical with less than a week of storage capacity was ferric chloride at Plant 1. Ferric chloride is the mostly used and frequently delivered chemical at Plant 1 and Plant 2 with less than 3 days between deliveries. Bleach was also identified as a chemical with frequent deliveries at Plant 1. Both ferric chloride and bleach are critical chemicals in order for OC San to meet permit requirements in their air quality and discharge permits. Table 3 was developed for OCSan to highlight the criticality (based on consequence score), average chemical use, and consequences of chemical interruption for chemicals used at Plant 2. Table 3: Summary of Chemicals Used at Plant 2 Figure 1 shows the overall risk score calculated for the chemicals used at OCSan. The score brings together the consequence, vulnerability and likelihood assessments. As can be seen in Figure 1, Bleach and Ferric chloride have the highest risk for chemical disruptions. Our full paper will include more details about the consequence, vulnerability and likelihood assessments and will provide a list of alternative chemicals that could be used to replace existing chemicals. Figure 1: Risk score for chemicals used at OCSan