Overview

Aqua struggled with water quality at a multi-tank site for years. Every summer during warmer weather, chlorine residuals in a 10.0 million gallon standpipe would drop to zero. Tank mixing was ineffective, as there was simply too much water and not enough usage. Efforts to add chlorine and test water samples required personnel on site round-the clock, and the problems were exacerbated with the three additional tanks on site feeding into the distribution system. We were hired to help overcome the water quality issues with the standpipe.

A test pilot project was conducted with an On-Site Hypochlorite Generation (OSHG) system, which showed impressive results. Essentially the tank was transformed into its own water treatment plant. After the successful pilot we were asked to design a new permanent system to produce sodium hypochlorite utilizing a 100#/day Microclor OSHG system.

System components included a stainless steel skid assembly, water softener, brine tank and pump, electrolytic cells, PLC control panel, DC rectifier, hypochlorite storage tank, hypochlorite metering pump, ammonia monitor, and hydrogen dilution blower. The project also required replacement of the existing mixer with a Tank Shark - Tank Mixing System. Finally, in order to facilitate the addition of OSHG equipment on site and to centralize sampling, the replacement of the existing Chemical Building with a larger two-room 600SF Sampling/Chemical Building was required.

Electrical upgrades were required on site, along with routing to the new building. The only location on site for the new building was in the vicinity of a steep embankment, so soil borings were required to ensure the stability of the foundation.

The 10.0 million gallon had an overflow height of 135’, with a domed roof taking the overall height to more than 150’. Designing the chemical (ammonia and hypochlorite) and air injection piping for the Tank Shark Mixer required an understanding not only of welded steel tanks, but of very large tanks, plus the weather conditions that could affect the system. Brackets were designed for the tank shell and roof for the new piping, and heat tracing and insulation of the piping was part of the scope of work to ensure freeze protection.

The new OSHG system now provides reliable and high water quality at the site. Chlorine residual readings from the 10.0 million gallon tank are easily maintained at 3.0 mg/L year-round, ensuring compliance with current regulatory requirements in Pennsylvania.