Several interdependent projects are described in this section which will show the laying of the ground work for the final efficiency improvements.

Realtime Dissolved Oxygen Monitoring

Situation

Both aeration blowers were being run twenty four hours per day just to maintain the dissolved oxygen (DO) levels above 1.0 ppm or so we thought. Determination of DO levels was accomplished by collecting samples and performing the chemical analysis in the utility’s lab.

Problem

Determination of DO levels was an onerous process and by the time the results were obtained the flow conditions in the aeration basins would have significantly changed as well as the biological oxygen demand. This situation resulted in running two 30 horsepower blowers 24 X 7.

Implication

The use of energy within the wastewater plant was intractable and operating efficiency improvements were not possible. Much labor was consumed doing DO testing and analysis and the results were just not that useful. The utility was not efficiently utilizing it’s resources including energy and labor resources. To further exacerbate the situation there were no indicators or pointers to assist the utility in finding it’s way out of the morass of inefficiency. All of this was costing the residents of Kachina Village money.

Now to be fair when the plant was built it was state of the art. Today, however, it is just not acceptable to run blowers without some indication of the DO within the aeration basins. Some utilities have variable frequency drives on their blowers but again there is no feedback loop or control to manage blower speed and efficiency.

Need Payoff

Installation of a DO/total suspended solids (TSS) instrument in each of the two basins was one of the first projects implemented by KVID. The instruments were attached to a PC running Red Hat Linux and the DO was plotted at 15 minute intervals using the spread sheet program of Open Office. The wastewater operators were just amazed to be able to watch the DO fluctuate over 24 hour periods and were not happy about the high TSS levels (2400 east, 3500 west) in the basins.

At this point in time the operators at least had the option of turning off the blowers when DO was higher than required. The blower motors were not VFD rated nor were they designed to operate at variable speed so only on-off control was used to conserve energy.

Results

Once the realtime DO/TSS monitoring was implemented the utility now had an idea of the dissolved oxygen levels in the aeration ponds. This made for some rudimentary, although manual, control of the blowers. A small increase in efficiency but still more was needed.

You might ask why Linux© was used to do the monitoring? There were two reasons. First, Linux was, and is, a free operating system that runs on PCs as is Open Office© . The second reason is that Linux does not require the big expensive hardware as does MS Windows© . As a result older, cast off (read free), PCs were used making the expense minuscule compared to utilizing MS Windows.