PTQ Q1 2024 Issue

6.0 7.0

Bioaugmentation program me started

Decreasing ABR

5.0

4.0

3.0

Increasing stress

2.0

1.0

0.0

Days

Ammonia Biomass Stress Index (BSI)

Active Biomass Ratio (ABR)

Figure 1 Refinery secondary wastewater treatment monitoring during upset

Step back. Review the data. Understand your specific constraints and targets. Accept that more than one param- eter may be responsible for the upset. Identify and correct the root cause, along with secondary causes. Adjust based on these insights and operating guidelines, and then be patient while the system recovers. Considering that biological systems recover slowly, often taking two to three sludge ages for full recovery, imple- menting contingency measures to maintain acceptable dis- charge water quality may be required. These measures may include supplemental coagulants, flocculants, antifoams, bioaugmentation, flow reductions, and other measures. Overcommunicate with production units during upset conditions; failure in communication can lead to extended recovery times if difficult wastewater loads are released from production units when the wastewater plant is vulnerable. Finally, never waste an upset: document more than you think necessary to ensure all lessons are learned, leading to new operating practices and optimised contingency plans. Case study: Downtime averted for refinery waste - water treatment under severe stress In this case example, a refinery wastewater influent was characterised by high levels of organics and ammonia, with frequent variations. While nitrifying bacteria are essential in the secondary treatment to remove ammonia, high-stress events saw their population being depleted. This caused ammonia levels in the effluent to shoot up, and the refinery had to curtail production to prevent potential environmen- tal impacts and discharge permit exceedances. The on-site Veolia team had been using the BioHealth monitoring technology to assess the health of the biological wastewater operation. When combined with the other data collected by the site’s operators, this enabled the plant to make optimal decisions regarding wastewater treatment and process unit adjustments. As shown in Figure 1 , the BioHealth tests indicated the BSI gradually increasing, with the ABR decreasing as the challenging conditions worsened. The nitrification process became unstable and completely inhibited as the bacteria population degraded. The production rate was reduced to ensure the plant’s effluent did not exceed regulations, so the wastewater system needed to return to normal rapidly.

With frequent communications of results between Veolia and the operations team and continued monitoring, it was decided to initiate a bioaugmentation programme. The BioHealth technology was used to identify the proper con- tingency treatment and dosage for fast and efficient recu - peration of the system. While the typical response to a nitrification upset could have taken one month or longer to recover, the data pro- vided by BioHealth to detect the problem and help identify the bioaugmentation solution allowed the plant to return to normal operation within just six days. Throughout the event, the operation team enacted the detailed monitoring programme well, so the discharge quality always remained in compliance. Conclusion Increased processing of opportunity crudes will likely con- tinue as there are clear financial incentives for refiners to include them in their crude diet. Even when trying to opti- mise crude blends and desalter operation, it is not always practical or economical to prevent all contaminations in the desalter brine effluent, and the wastewater treatment plant should be equipped to handle these while respecting dis- charge quality limits. For the refinery’s wastewater facility to operate efficiently and sustainably when faced with the challenges attached to these heavy crudes, new practices and solutions must be implemented. Enhanced monitoring, data-driven deci- sions, and a good understanding of the treatment basics combined with openness to apply these basic rules to new conditions will reduce the frequency of wastewater upsets and increase speed of recovery when they do occur. This will enable the plant to maintain operation while consist- ently respecting discharge limits and regulations. Shane Lund is a Senior Application Engineer at Veolia Water Technologies & Solutions based in Minnesota. With more than 24 years of water treatment experience, he provides technical and sales sup- port. He has also co-authored several papers on biological wastewater treatment systems in refineries and regularly makes presentations and provides training on the topic. He has a BSc in biology from St. Cloud State University and an Associate of Science in water technologies from St. Cloud College.

PTQ Q1 2024