Jun 29, 2018

Heavy Rain Brings Heavy Metals

Emergency preparedness & contingency planning for storm water treatment

Emergency preparedness & contingency planning for storm water treatment
Emergency preparedness & contingency planning for storm water treatment

The frac tank contains the clarifier, which provides solids removal.

The Gulf of Mexico endures its fair share of storms, making the sub-tropical coastal plain’s infrastructure vulnerable to flooding from heavy rains and storm surges in cases of severe tropical depressions or hurricanes. As a result, managing an industrial facility on the Texas Gulf Coast can create challenges during these flooding events. Operators must be prepared for the worst-case scenario, but even with emergency preparedness, severe weather and unexpected volumes of water can overwhelm any facility.

It was an event such as this that impacted a major petrochemical company on the Gulf Coast in spring 2017. The plant had suffered a series of heavy storms, resulting in flooding that could not be managed by their existing systems. The excessive water picked up process metals, including copper and zinc, and organic compounds (measured as TOC) to concentrations beyond the capability of their effluent treatment plant. More than 3 million gal of storm water had to be stored in both permanent and temporary storage tanks. Ultimately, the storm was declared an event of force majeure, providing the facility additional time for remediation of the excess storm water that needed treatment or disposal by external suppliers.

Emergency preparedness & contingency planning for storm water treatment

Flooding at the plant could not be handled by the existing system.

Planning & Preparation

The company wished to treat the water on site and avoid the excessive costs of off-site disposal. Within 24 hours of an initial call to BakerCorp, a treatment plan, scope of work and budgetary proposal were submitted to the company’s management. In the week that followed, the provider met with the facility’s operations management; engineers; and environmental, health and safety personnel to discuss the method of treatment and project logistics, in addition to conducting a site walk and review.

During this time, BakerCorp also secured water samples for bench testing. Comprehensive bench testing allowed it to track onsite treatment efficacy to required copper and zinc levels. Tests were completed in 48 hours and a turnkey mobile water treatment system was offered, along with a mobilization plan and time frame for treatment.

In the proposed strategy, a mobile electrocoagulation (EC) system would reduce the levels of copper and zinc for discharge to the facility’s effluent treatment plant. Designed to lower multiple dissolved metal concentrations in a single-unit process, the EC system would efficiently treat both copper and zinc at the same time. After the EC system and solids separation process, granular activated carbon would further reduce the TOC that the EC process did not. Target levels for treatment were set at less than 0.25 ppm zinc, less than 0.15 ppm copper and less than 20 mg/L for TOC.

The solution would include several unit processes within two broad categories: the EC and solids handling process, and post-treatment of the water utilizing filtration and adsorption. Equalization, electrocoagulation, defoam, flocculation, clarification, sludge thickening and a filter comprised the EC and solids handling portion. Post-treatment on the clarified water would include sand filtration and bag filtration to protect against any solids carryover and media filtration to address organics. Additionally, pH adjustment pre-EC and post-treatment were included if required, as well as polymer dosing to shorten flocculation time post-EC.

The solution also included using an EC-250 mobile treatment trailer, several clarification tanks and basins, a filter press, a Dual 10K duplex media filter along with the granular activated carbon, pH adjustment and chemical dosing equipment, equalization and acid tanks, and all piping, hose, fittings and containment berms for each piece of the system. Additionally, a generator was provided so that the system could be self-sufficient, independent of the facility’s operation.

Emergency preparedness & contingency planning for storm water treatment

A mobile electrocoagulation system reduced the levels of copper, zinc and organic compounds.

Treatment Trials

During the purchase requisition phase, BakerCorp staged equipment in the area, secured additional required training for personnel working in a petrochemical plant, and planned the mobilization and equipment set-up on paper. On June 1, 2017, the team and equipment were mobilized for site placement.

From the initial scoping to implementation, flexibility was designed into the treatment system. Flexibility in handling changing water quality is critical, as contaminant concentrations can change in collected and stored storm water due to stratification from salinity and the effect on settling. The water quality drawn off a large storage tank will change as it is treated, and this change was exhibited in this case. The onsite adaptability of the EC mobile treatment trailer made it a key consideration for successful treatment of the contaminated waters.

Throughout the treatment process, the waste streams varied in salinity and pH. If unchecked, such variations can mitigate the effectiveness of treatment. Aided with data monitoring tools available to the mobile treatment trailer, technical service engineers adjusted operations according to the varying levels of contaminants.

Filtering water at an industrial facility heightens the need for the treatment system to maintain its performance and reliability regardless of changes in the effluent. Despite the challenges, the project was completed in less than two months.

Checking it Twice

Following successful completion of the initial storm water treatment project, the company encountered an upset condition at the facility, creating levels of zinc in its storm water that its effluent treatment plant could not handle.

For the follow-up project, a new temporary filtration system effectively treated the contaminated water, while keeping expenses below the cost of hauling the water off-site. With a target of reducing the zinc concentration from 7 ppm to 0.25 ppm, a flexible system allowed for effective and economical on-site treatment. Within one month, zinc levels were reduced to the target range in the water storage tanks.

BakerCorp installed an EC-250 mobile treatment trailer to provide adaptability to the varying conditions. The addition of its CL-250 mobile clarifier system led to a reduced system footprint, an important consideration for an industrial facility where space to operate can be tight.

During the project, the treatment system was required to sustain a flow rate of 200 to 250 gpm in order to not exceed the onsite wastewater treatment plant’s volume limits. However, shortly after beginning treatment, the customer needed to use facility storage tanks sooner than originally expected. BakerCorp adjusted the flow rate to 350 gpm and treated seven days a week to clear the tanks of contaminated water ahead of schedule.

During the two treatments that occurred over a 10-month time span, the total volume of water treatment was more than 4.5 million gal. In each project, all contaminant levels for zinc, copper and TOC—tested daily—were maintained at or below the target levels. While it is not always possible to prepare facility infrastructure for worst-case scenarios, secondary containment and treatment of excess wastewater from storm events can be part of a prudent preparedness plan. 

About the author

Mehrzad Emanuel is vice president of filtration and Brian McNeil is business development manager, water treatment technology, for BakerCorp. Emanuel and McNeil can be reached at 512.392.2660.

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