Odor from Wastewater Processing Facility Resolved

Background

Gross-Wen Technologies (GWT) got its start in 2014 while Dr. Martin Gross was working with his professor, Dr. Zhiyou Wenat, at Iowa State University. The two discovered a ground-breaking, effective, economical and reliable method for the treatment of municipal wastewater. GWT’s patented Revolving Algae Biofilm (RAB™) technology utilizes vertical conveyor belts on which algae grow. The algae remove nitrogen and phosphorous from the wastewater by feeding on it. Using sunlight and carbon dioxide from the atmosphere, the algae rapidly grow until they can be harvested. GWT processes already-treated wastewater from the City of Slater with the RAB™ operation. Once this nutrient-rich algae is harvested, it is repurchased by GWT and pelletized. The resulting algae pellets are then used in various applications – including as fertilizer – thereby leveraging the valuable byproducts of municipal wastewater to help offset processing costs.

The Problem

Slater, Iowa has been operating its RAB™ operation for a year-and-a-half, with 30 belts actively collecting algae. Now, the project is about to move into its next phase, which involves one of the most odor intensive parts of the process: the dewatering and drying of the algae. This step produces H2S and mercaptans. GWT anticipated this and took a proactive approach to odor control. With a children’s playground located at the entrance of their processing plant, and a large residential community nearby, they prioritized being good neighbors and responsible environmental stewards. GWT knew that proactive odor control was essential.

The Solution

Following extensive conversations with GWT, Industrial Odor Control presented GWT with two reasons to split the odor control system in two. First, constructing a single, larger system would prove to be a logistical nightmare when it came to transport the tanks. This would require road closures and permits to transport the tanks to their location. Second, having two standalone systems offers a more flexible solution: each system consists of an adsorber tank that is 10 feet tall and 10 feet wide. Each has an American Fan VCS, 65%, 3-phase blower motor running with a variable frequency drive. They can run from 0-5,000 CFM. The systems are ducted to a 33,000 square foot greenhouse where the dewatering and drying process takes place.

Having two systems in place provides a backup option. This setup ensures continuous control even during system maintenance, keeping operations running smoothly. It is also beneficial during times of low airflow, as the volume of air scrubbed can be scaled back accordingly. Combined, the two systems can provide up to 17 air exchanges per hour. An odor scrubber is only as good as the media you put in it. At the heart of each system is 6,500 lbs. of Norit Darco H2S LP activated carbon. This robust carbon was developed specifically for the wastewater industry and is designed to perform reliably in high-humidity environments, outlastoing traditional carbons by three to five times.

Gross-Wen Technologies currently operates three commercial RAB™ systems. In addition to the Slater facility, the other operations are located in Pasco, Washington where 130 belts are in use and Iowa City, Iowa, with 4 belts. To learn more about their process, please visit