Custom Wastewater Disposal Equipment & Solutions

Job Was Conducted In 2001
Unocal 76 Believed In An Idea And Funded The
Manufacture Of 2 SC-NG550 Turbo Blower Evaporators

Evaporative Systems, Inc., successfully completed a major Zero Liquid Discharge, (DISPOSAL) contract for Unocal 76 in Parachute Colorado. The beginning amount of 2.8 million gallons plus an additional 1.4 million  gallons of rain water for an estimated total of about 4.2 million gallons was completed with 95 days of actual operation.

The 170,000 mg./l. sodium sulfate solution was a by-product of the Shale Oil Refinery operations from the early 1980's which has since been mostly dismantled.

This waste water went through many stages during the past 20 years primarily because originally the waste water was in excess of 20 million gallons and very toxic containing high levels of Arsenic, Selenium, Organics and other toxins. The waste water had to be treated to a level where it could actually be handled and disposed of safely and economically, then the waste water original volume had to be reduced by method of atmospheric evaporation by means of an automated manifold type pond misting application,  then a method of satisfactory disposal had to be researched. Since the waste water contained mostly Glauber Salt, Gypsum and Anhydrous salts it was previously determined through several small scale heat exchanger type tests that conventional evaporation equipment could not handle this type of job successfully. Glauber Salt in it's pure form has a melting point of around 90 deg. F. and a very high solubility curve at high temperatures.

In May of 2000 the pond contained 5.5 million gallons @ 78,000 mg/l. and about 1 to 4 inches of salt crystals on the pond bottom. During the year the pond level was lowered to around 3 million gallons by the misting system and by our arrival in May of 2001 the pond contained roughly 2.8 million gallons @ 170,000 mg./l. and up to roughly 4' of precipitated salts on the pond bottom caused by differential crystallization from the cold winter months associated with the high total dissolved solids level. Once salts are precipitated out in this manner they rarely re-dissolve back into solution. During the job about 6" to 1' of the salt dissolved back into solution from warm pond temperatures and the resulting accumulation of more than 1.4 million gallons of rain water.

This particular water was like non we had seen before, we encountered few problems concerning maintenance and operation of the equipment once the operating parameters were determined of the newly designed equipment. The biggest problem encountered through out the job was getting the water pumped up to the equipment with over 30' of discharge head. This type of water tended to freeze and / or solidify with differential crystallization with ambient temperatures around 65 to 69 deg. F. Being in the state of Colorado with the cooler temperatures associated with the wind chill factor, we were unable to operate our intended schedule of 24 hour operation on a daily basis. We basically worked each day around the clock as long as the temperature allowed for continuous feed. The most common typical day was about 12 to 14 hours of operation.

It wasn't uncommon to see a frozen, (crystallized) pond each morning with ambient temperatures of 60 deg. F. We were lucky in the fact that once the pond temperature reached above 65 deg. F. usually from (8:00 to 11:30 am,  all it took was a little fresh water, heat or a sunny morning to re-liquify the pump area and discharge lines after the pump and/or the pump discharge lines had (solidified / frozen / crystallized). One draw back to this job was the typical equipment fill up time required for each cycle restart was about 1 to 1 1/2 hour per evaporator.

Disposal of the hazardous brine consisted of evaporation and individual run time concentrations to near saturation values, (50%+) before discharge into concrete containment areas. The typical (4 to 6), 1,000 gallon per day discharge loads was then mixed with 1 1/4 part quicklime by weight and solidified for approved non hazardous disposal back into the mine. The efficiency of the system was roughly 89 % total evaporation of the pond water with the remaining 11 % discharged and mixed by volume. Total evaporation and discharge per day was roughly 42,000  to 62,000 gallons per day depending on the ambient temperature as well as the temperature of the pond water and the pond surface evaporation during the day. When the pond temperature at the pump inlet reached around 80 to 90 deg. F. this allowed for the Glauber Salt laying in the bottom of the lined pond to dissolve back into the liquid raising the overall tds., from 200,000 to from 250,000 to 350,000 mg/l.. to un-measureable towards the end of the job.  In other words this pond water changed constantly on a day to day, day to night basis, which resulted in constant change in operating procedures. For the entire job, once the operating procedures were learned we evaporated and concentrated each discharge load of water to the point where we could not push further any more heat from the 30 hp. 2 stage turbo blower, burner flame, and fire tube setup, through the rotating liquid contained in the Submerged Combustion System vat. " This was no push button type job".

Our best performance was in early July with ambient day time temperatures exceeding 100 deg F.,  accompanied by the following warm nights, we were able to produce 850,000 gallons of total disposal in 15 days.

During this time period there was no accumulated measurable rain, and an estimated 5,000 to 10,000 gallons per day of pond surface evaporation and 5,000 gallons of concentrated near saturation value discharge per day. During this period and the warm ambient temperatures, we had little difficulty obtaining a constant supply of pond water around the clock.

Note: Brine reaction @ 170,000 mg./l. with quick lime (minimal to none),

          Brine reaction with quicklime began at roughly 35%  and maximized @ 50% plus

We utilized (1) Model 200 HT-R Evaporator and (2) of our newly designed Submerged Combustion Evaporator/Concentrators. These 2 units were built in 1992 by US Enertek located in Farmington NM originally as water disposal evaporators, and laid to rest several years there after.. We purchased these 2 non working units and completely rebuilt and modified to our new specifications to handle the Unocal 76 Shale Oil Refinery waste water evaporation and concentration process.

Note: The equipment utilized for this job went through an intense and exhaustive HAZOP conducted by John Dietzman V.P., Unocal 76, as well as an independent engineering firm in Tucson, Arizona,  related to equipment design, safety, and equipment operational strategies. This HAZOP was actually conducted for a proposed job with MolyCorp operations in Mountain Pass CA., owned by Unocal 76.

The Shale Oil Project, final waste water disposal job was probably the toughest job ever encountered by this type of equipment, and after 95 days of operation the equipment was still in 100% satisfactory condition other than a little abuse on the paint jobs, to be utilized for other waste water disposal jobs. Towards the end of the job we were basically pumping  near saturation value liquid into the Evaporators from the pond bottom and still concentrating it further..

Text: By Robert L. Farley