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The Challenge
Anguil Environmental Systems was asked to supply an oxidizer and packed tower air stripper to treat a 65 gallon per minute water stream containing significant concentrations of Diesel Range Organics (DRO), Volatile Organic Compounds (VOCs) and Total Suspended Solids (TSS). The customer was sending the wastewater stream through a cooling tower which was continually fouling from the DRO present in the water. Significant maintenance costs and production downtime were incurred every time the tower was being brought out of service for cleaning. In addition, the customer was trying to achieve zero VOC emissions from their facility.
The Solution
Application engineers at Anguil determined that a Regenerative Thermal Oxidizer (RTO) would meet the customer’s needs but were skeptical that the air stripper would function properly given the customer supplied water characteristics. Anguil was engaged to evaluate the water stream for the air stripping application. Review of the supplied water analysis indicated that concentrations of the heavier Diesel Range Organics (naphthalene and higher) were beyond their solubility limits. Hence, the presence of free product in this water stream would quickly cause any air stripper to foul, detrimentally impacting stripping performance and potentially creating a safety hazard. Anguil recommended that the customer evaluate oil/water separation and emulsion breaking to remove and potentially recover the free product prior to entering the air stripper.
The Result
Using water samples obtained from the customer, an initial bench evaluation of oil/water separation was conducted. Upon receiving the samples, Anguil realized that either the customer-supplied water analysis was incorrect or that the water samples received were not representative of the customer’s process water since the presence of free product was not observed. The emulsion breaking tests were performed anyway, predictably meeting with little success. In addition to the emulsion breaking tests, Anguil attempted to coagulate the water to determine if this approach would be suitable, determining this method had merit.
Based on results from the initial separation study, Anguil recommended two courses of action. First, the customer would redo their analytical water analysis using suggested test methods to improve confidence in the treatment design requirements. Based on the results of the second round of analytical tests, Anguil suggested that a two stage pilot study be conducted. For Stage 1, Anguil representatives would perform treatability studies on site via jar testing. Based on the results obtained from Stage 1, Anguil engineers would perform a full scale, onsite pilot with the appropriate equipment for Stage 2.
Stage 1: Anguil representatives traveled to the site and performed jar tests directly with the process water in question. Since the process water was at a temperature of 110-120 oF, it was advantageous to work with the process directly rather than trying to ship samples off site possibly compromising their integrity from cooling, biological action or chemical reactions from long hold times. After a number of trials, they successfully determined that the water could be coagulated by raising the pH from 4 to 8.5, utilizing a poly aluminum chloride (PAC) based coagulant blend and a standard polymer. After coagulation and filtration, color, turbidity and solids content were reduced. Anguil then sent the untreated and treated water for third part lab analysis to determine the overall effectiveness of the process. The results were promising and the customer elected to move forward with Stage 2 of the pilot study.
Stage 2: Based on the site constraints and treatment goals, Anguil modified its pilot clarification system to perform the second stage of the study. Equipment arrived onsite,was unloaded and placed within the facility. A generator was rented since the facility could not easily supply the required power. Anguil then proceeded to unpack and plumb the pilot system into the existing process piping.
Once everything was set-up, pumps primed and running, the operator filled the tank with process water and began processing using the chemical formula determined in Stage 1: Raise pH > 8.5 using 50% caustic solution, add 300 ppm coagulant, add 1 ppm polymer. As expected, the clarifier influent demonstrated a good floc which quickly began to settle to the bottom of the clarification tank. With continued processing, clarity improvements in the clarification tank became noticeable as submerged parts of the tank became visible as the initial dirty water was displaced by the coagulated and clarified water. Water samples pulled from the clarifier effluent were obviously cleaner than the raw process water, and with continued processing acceptable clarity was achieved.
After successfully demonstrating the clarification process, treated samples were pulled and tested using the same test protocol used in Stage 1. In addition, a sludge sample was sent for benzene analysis in order to determine if the sludge would be considered hazardous. Sludge production rates were quantified by coagulating, flocculating and filtering specific volumes of process water. Filtered samples were wrung dry and air dried for several days. Wet and dried samples were weighed.
The qualitative and quantitative results met the customer’s expectations and treatment goals. The chemical coagulation protocol and clarifier in this pilot work were able achieve a DRO reduction of 85% or greater and an 80% reduction in TSS. Since Anguil was proposing a ballasted floc system for the final treatment system to handle the design flow rate of 65 GPM, another set of samples was taken for ballasted floc testing which achieved similar DRO removal rates but improved on the TSS reduction to less than 1 NTU. After reviewing the sludge production rates and potential hazardous classification for the sludge, the customer asked Anguil to recommend a sludge dewatering system. Further, after reviewing the treatment system capabilities and facility requirements, Anguil recommended removing the air stripper and oxidizer from the scope of supply as it was determined that removing the heaviest organics would solve the facilities heat exchanger fouling problems, and the limited VOC loading did not justify the use of an oxidizer.
Anguil was able to guide the customer through the equipment design and selection process by identifying and rectifying shortcomings in the analytical data, avoiding time and cost specifying and designing equipment which would not address the customer’s project goals. Ultimately, the main benefit of Anguil was determining a solution which did meet the customer’s objectives despite the fact that the selected solution differed greatly from the original request. Onsite jar and pilot tests allowed the customer to become educated and familiar with the treatment process while understanding the benefits, capabilities and trade-offs of the proposed system. Further, being on site allowed Anguil to really understand the customer’s needs and process, allowing them to identify customer process variables which could potentially affect treatment system performance and provide seamless integration of the new treatment system into the existing process.