NALMET® SOLUTION MEETS HIGH MERCURY CRUDE WASTEWATER TREATMENT CHALLENGE WHILE REDUCING PRODUCTION COSTS

THAILAND PLANT REDUCES PRODUCTION COSTS WHILE COMPLYING WITH STRINGENT ENVIRONMENTAL REGULATIONS

High crude prices, together with tighter refining margins, have driven more and more refineries to process challenging or “opportunity” crudes. Refineries can acquire opportunity crudes at a discounted price due to either known processing challenges or the unknown characteristics and properties of new crudes.

BACKGROUND
Crudes from the Far East, particularly from the Gulf of Thailand, contain high levels of mercury and arsenic that greatly challenge Thai refineries. The Thai government’s strict industrial wastewater discharge regulations mandate a discharge limit of 5 parts per billion (ppb) for mercury and 250 ppb for arsenic. However, when refiners process opportunity crudes with high mercury and arsenic content, the mercury level in the wastewater may rise to as high as 10-3,000 ppb, and the arsenic level may reach 100 ppb to a few thousand ppb.

SITUATION
Before beginning processing of high mercury and arsenic crude, a refinery in Thailand sought the support of Nalco Champion to treat the mercury and arsenic in their wastewater treatment plant in order to comply with discharge-related regulations.

SOLUTION
Nalco Champion conducted an audit in the refinery wastewater treatment plant (WWTP) to assess its mechanical set-up and the feasibility of treating the arsenic and mercury. Based on the findings, Nalco Champion proposed a comprehensive chemical solution aimed at removing oil, total suspended solids (TSS), mercury and arsenic in the Induced Air Floatation (IAF) unit. The Nalco Champion team integrated patented Nalmet® technology into the chemical treatment program for primary wastewater treatment application.

RESULTS
Nalco Champion’s solution effectively removed these pollutants in the WWTP primary treatment while also preventing toxicity from spreading to the downstream biological treatment system. The mercury and arsenic levels in the final effluent from WWTP complied with the discharge-related regulations put in place by the local government.

When the refinery began processing the high mercury and arsenic crudes, the mercury and arsenic went to the wastewater through the desalter brine and the crude tank drainage. The concentration of mercury in mixed wastewater was 10-160 ppb and the arsenic concentration was at 20-1,200 ppb.

Since implementing the Nalco Champion chemical program into the WWTP primary treatment, the average mercury removal efficiency was 94 percent, resulting in WWTP effluent mercury concentration of less than 3 ppb.

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The arsenic removal efficiency was impacted by limited chemical reaction conditions at the site and broad fluctuations in the influent arsenic concentration. The average arsenic removal efficiency was 75 percent. Despite the influent fluctuations and limited chemical reaction conditions, the Nalco Champion treatment program kept the arsenic concentration at the WWTP effluent stable at less than 180 ppb. Eventually, both the WWTP effluent mercury and arsenic met the government wastewater discharge limits.

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CONCLUSION
Nalco Champion’s solution allowed the refinery to safely and successfully treat mercury and arsenic in the wastewater treatment plant, enabling the processing of high-mercury and arsenic crudes while complying with environmental regulations and reducing production costs.

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A Thai refinery challenged by opportunity crudes implemented Nalmet technology to reduce production costs while complying with stringent environmental regulations.

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