| Manure storage is sometimes limited and over application of manure on fields is dangerous to the environment, especially ground water. Filtration systems using reverse osmosis (RO), are one alternative approach to reusing waste water and eliminating risk for manure spills or harming the environment. There are various challenges involved when trying to optimize this system, one of which is membrane fouling upon the RO filters. The rapid increase in pressure and reduced permeate generation due to fouling is problematic. To address this issue, antiscalant was added to the feed and the feed stream was pH adjusted using sulfuric acid or hydrochloric acid. In order to determine what foulants were present on the membrane, some of the membranes were dissected and tested using scanning electron microscopy (SEM), energy dispersive x-ray (EDX), chromatic elemental imaging (CEI), Fourier transform infrared technology (FTIR), and effervescing. Testing indicated organic and silcate scaling were present under all operating conditions. In addition, there was a greater degree of scaling using non pH adjusted feed versus pH adjusted. The use of air stripped water processed through the RO system was used for all the experiments at the pH of 5.5, 6.5, 7.5 and 8. Sulfuric acid and hydrochloric acid were used to lower the pH of the air stripped water (normal pH of 8) and the various acid runs were compared in the study. After optimizing the system, and using permeate production as a gauge, the system performed best at a feed pH of 6.5 using sulfuric acid and an appropriate dose of antiscalant, determined by the Avista Advisor modeling software. The use of hydrochloric acid was very expensive when pH adjusting versus the use of sulfuric acid for pH adjustment. Operational costs and capital costs were also determined. |
