Microbial Control, Nutrient Compatibility & ORP Management

“Infinite Harvest chose to implement Silver Bullet because I did not have to maintain the system myself. I did not have to buy or handle any hazardous consumables. And the service program Silver Bullet offers is not available from any other water treatment provider.”
          – Jim Romano, Infinite Harvest Director of Operations

The Grower’s Need: A More Effective & Safe Water Treatment Solution

Infinite Harvest, a Colorado-based commercial hydroponic producer of high-quality leafy greens, was motivated to implement a new water treatment system that would provide more effective control of algae, biofilm and plant pathogens; maintain an elevated oxidation reduction potential (ORP) levels; and eliminate the handling and storage of hazardous chemicals.

Facility Profile

The Infinite Harvest facility uses a closed loop irrigation distribution and recycling system that is topped off with filtered municipal water and fertilizer nutrients on a continual basis. The facility’s previous water treatment program consisted of chlorine dioxide (ClO2), which was added as the primary disinfectant chemistry in daily batches to maintain ORP levels.

Infinite Harvest uses an integrated recycling, composting and regenerative system to minimize waste while increasing energy and water efficiencies. All seeds and harvested produce are Good Agricultural Practices (GAP) certified and are distributed to local restaurants and grocers.

Nutrient Compatible, Safe and Professionally Serviced Water Treatment Solution that Controls Pathogens

Water management plays a critical role in the function of Infinite Harvest’s facility. Silver Bullet initially engaged Infinite Harvest in early 2018 to collect preliminary water baseline samples and site survey data. Jim Romano, Infinite Harvest’s Director of Operations, said the company chose to implement Silver Bullet because of multiple benefits:

  • A sustainable, “green chemistry” – based solution that was proven to provide bacterial, fungal and phototoxicity control

  • A professionally designed, engineered, and installed water treatment system that is compatible with nutrient blends

  • Silver Bullet’s service, maintenance and water analysis programs

The Silver Bullet Solution: AOP and UV Combination System

Silver Bullet installed a water treatment design during mid-April 2018 that consisted of the combined Silver Bullet oxidant gas and UV disinfection system. Baseline water samples also were taken immediately prior to the start-up of the Silver Bullet technology and again after the UV units were activated.

During the first few weeks of treatment, full water analysis was conducted to provide a trending nutrient composition profile to demonstrate Silver Bullet’s compatibility with the nutrient blend and ensure no nutrients were being precipitated or otherwise altered so as to inhibit plant nutrient uptake. After both macro and micro nutrient elements were shown to be unaffected, Silver Bullet adjusted the monitoring program to focus on microbial analysis and electro-chemical field analysis including dissolved oxygen (DO) and ORP.

After roughly 50 days into the evaluation, the combined Silver Bullet AOP-UV system was modified and adjusted while the tapering existing CLO2 treatment program was phased out. ORP levels fluctuated during this transition period before reaching a steady state. During the modification phase, the UV systems were turned off for a few weeks. The installation modification was made to test the stand-alone disinfection ability of the two Silver Bullet systems in the highly-challenged water stream. After approximately two and a half weeks, the UV systems were re-activated for the duration of the evaluation.

Confirmed Nutrient Compatibility

To confirm nutrient compatibility, the water samples taken following the activation of Silver Bullet’s treatment system were analyzed for a full nutrient profile. Iron and manganese were singled out as having potential precipitation issues. The results show that from a nutrient perspective, the system remained in equilibrium across the multiple sample locations throughout the evaluation period. Analysis of total and dissolved metals shows precipitation did not occur as a result of Silver Bullet’s treatment and overall, the Silver Bullet water treatment program is fully compatible with Infinite Harvest’s nutrient blend.

Proven Microbial Control

Bacteria levels were intensively monitored throughout the evaluation because pathogens in the irrigation system had been problematic for Infinite Harvest before Silver Bullet was installed. Heterotrophic Plate Count (HPC) levels of the samples trended closely, an indicator that the closed loop system was in equilibrium. The HPC level of samples taken shortly after Silver Bullet was activated showed significant decreases from the pre-treatment baseline (approximately 450,000 cfu/cc).

Per the pilot protocol, the UV-direct disinfection systems were turned off to conduct an installation modification. HPC levels did briefly increase before dropping back to previous low-level range levels that were maintained through the end of the evaluation. The UV-direct disinfection system maintained bacteria levels throughout the demonstration.

ORP Management Optimized

ORP levels were somewhat variable during the initial weeks of the evaluation project. Following the addition of a second HO230 unit, ORP values increased to the highest observed range and were maintained at levels from 300 to 400 mV, thus meeting the client’s objectives.

Effective UV Treatment Despite Unique Challenges

During the evaluation, Infinite Harvest changed the growth media to a more inert form which led to the UVT increasing to a satisfactory level. Despite changes in make-up water, accumulations of organic matter from plants and changes in nutrient formulation, Silver Bullet’s oxidant gas and UV disinfection system has controlled microbial levels to the satisfaction of Infinite Harvest management.

Consistent Plant Growth

Plant health was visually monitored throughout the evaluation and no phytotoxic impacts were attributed to Silver Bullet’s treatment solution.

Silver Bullet: A Safe, Sustainable Water Treatment Solution for Controlled Environment Leafy Greens Facilities

The Silver Bullet water treatment system met all of the Infinite Harvest’s primary expectations.

Extensive nutrient monitoring throughout the evaluation showed no significant changes in nutrient composition and the appropriate iron and manganese levels were achieved. These results confirm the compatibility between the nutrient blend and the Silver Bullet treatment systems.

Microbial levels, as measured using HPC and total coliform metrics, were maintained below the baseline values throughout the duration of the evaluation. ORP levels were increased and were maintained within the client’s desired range for the duration of the evaluation. No reported pathogenic outbreaks, diseases or phytotoxic effects that could be attributed to the Silver Bullet treatment process were observed.

Infinite Harvest’s satisfaction with the results of the treatment evaluation has led the company to implement Silver Bullet’s technology as the facility’s permanent, stand-alone water treatment process. Infinite Harvest’s Jim Romano highlighted the positive impact working with Silver Bullet to improve his water quality:

“Working with the service, science and engineering staff has been my favorite part of my experience with Silver Bullet. I can see us working together for a long time.”