Industrial Control of Odor Using Specialty Enzymes

Case Studies

Case Study

ZymeOutTM has been tested by sugar beet companies where it is added to lagoons to prevent the generation of hydrogen sulfide gas. The companies were concerned about odor and government fines for exceeding H2S levels. Wastewater was generated during beet washing,transportation and beet sugar production.  The wastewater flowed into a nearby lagoon for treatment and eventually flowed into a local creek.  The main issue was strong smell of hydrogen sulfide near the lagoon during the production season and precipitation of black sludge in the lagoon requiring periodic dredging.

ZymeOutTM was added to the wastewater as it flowed into the lagoon at an average flow rate of about 4-10 gallons per minute (15 – 38 L/min). The enzymatic composition was added to mix with the wastewater resulting in a enzymatic concentration in the range of 10-25 ppm in the wastewater.  It was observed that after this addition had been continued for about 20 days, the smell of hydrogen sulfide became less and after 60 days, there was no detectable hydrogen sulfide smell near the lagoon.  The lagoon water also became very clear and there was no black precipitate settling at the bottom. The reduction of sulfides helps prevent the growth of algae and other types of anoxic bacteria that can produce foul smell and turbidity in the lagoon.

Lab Study

Three continuous stirred tank reactors were operated with sulfate and organic feed, with nitrogen gas being bubbled to remove any hydrogen sulfide formed. The control reactor had no additive. In Reactor 2, Hypochlorite was added and in Reactor 3. ZymeOutTM was added on Day 3. The concentration of  hydrogen sulfide gas was measured in the exit gas as shown in the graph below. ZymeOutTM was able to inhibit the production of the H2S significantly better than hypochlorite. On a 25 day period, based on the total H2S produced, ZymeOutTM was 60% more effective than hypochlorite.

ZymeOut vs Chlorine

Lab Study

A test was conducted at bench scale using four sealed 5-gallon containers.  Each 5-gallon container was essentially a sealed SRB landfill reactor filled with waste drywall (calcium sulfate), a nutrient source and leachate from a landfill (containing SRB) that had hydrogen sulfide odor issues. The leachate resulted in strong active SRB colonies within the SRB reactor.  Nitrogen gas was continually passed through the containers to eliminate any oxygen that could suppress hydrogen sulfide production and to provide a gas flow in which hydrogen sulfide produced in the reactors could be measured.  Various levels of ZymeOutTM were then added to selected containers and the hydrogen sulfide levels were monitored in the nitrogen stream from each of the containers over time. Low levels of ZymeOutTM at 0.01% (100ppm) to 1.0% (10,000ppm) controlled SRB growth and stopped hydrogen sulfide production for one day to greater than 90 days (completion of the test). The control reactor had H2S levels from 250 to > 800ppm which was the detection limit on the H2S sensing instrument.

Lab Study

The following experiments were conducted in 50 mL test tubes with 30 mL of wastewater.  Each test tube was equipped with a tube fitted to a fritted glass piece to disperse the injected gas into small gas bubbles.  The exit gas from each tube was monitored and gas composition was analyzed using a gas chromatograph.

Untreated Waste Water

Untreated Waste Water

Less than 3 ppm ZymeOutTM

Treated with ZymeOut

These results showed that less than 3 ppm ZymeOutTM  eliminated the formation of hydrogen sulfide, inhibited the formation of ammonia from about 25 ppmv to 5 ppmv, and increased methane production from about 24 ppmv to 31ppmv in the wastewater under anaerobic conditions.