INTRODUCTION
The California state legislature has mandated that reclaimed water (Title 22 water) be utilized for industrial applications in order to conserve the state?s fresh water supply. Because cooling systems are typically the largest consumers of water in an industrial plant, cooling tower make-up is the most likely candidate for use of reclaimed water. Although reclaimed water potentially offers many environmental, political, and economical benefits, its use poses many challenges to the successful treatment of an industrial cooling system. This paper presents the major concerns associated with the use of reclaimed water as cooling tower make-up, identifies the required monitoring and control schemes, and discusses the treatment results at the first California oil refine~ using reclaimed water (treated Title 22 water) for cooling tower makeup.
The quality of reclaimed water can vary significantly from that of typical cooling tower make-up. Certain constituents contained in the reclaimed water present challenges to the successful control of corrosion, deposition, and microbiological growth in a cooling system. The California State Legislature, however, has mandated the use of reclaimed water to prevent depletion of the state?s fresh water supply. The quality of this reclaimed water is governed by Administrative Code Title 22, hence, this water is referred to as Title 22 water. The driving forces behind its use stem from several consecutive years of drought conditions, dwindling options for importing water into the state, and escalating costs for imported water. In addition, several million liters of potentially useful water are discharged to the ocean each day. The use of reclaimed water was deemed necessary to meet the fresh water requirements of all users in the state.
One of the largest consumers of fresh water in California is industrial cooling systems. Prior to 1995, a few Power and Independent Power Producing (IPP) plants in the state switched to using reclaimed water for make-up to their cooling system(s). The design of the heat exchange equipment in most of these plants can be characterized as having high cooling water velocities and low cooling water skin temperatures, i.e., >5.0 ft/s (1. 52m/s) and<100F (3 S°C), respectively. These desirable cooling water conditions minimized several of the concerns associated with using reclaimed water for cooling tower make-up. Unfortunately, a significant percentage of the heat exchange equipment found in oil refineries and chemical plants do not always operate under the favorable conditions existing in Power and IPP cooling systems. In refinery cooling systems, it is not unusual to find heat exchangers with cooling water velocities <2.0 ft/s (0.61 m/s) and/or water-side skin temperatures > 140°F (60°C). These severe water-side conditions have always proved to be the greatest challenge to a cooling water treatment program. This, coupled with the inherent concerns associated with the quality of reclaimed water, led most refineries and chemical plants to avoid its use in their cooling systems.
Although the number of industrial plants in California using reclaimed water in their cooling systems was small, serious talk of legislation that would mandate its use was prevalent. Drought conditions and threats of reduced water usage levels resulted in numerous evaluations of reclaimed water for tower make-up. Since 1988, the Betz TraveLab@, a mobile laboratory equipped with evaporative cooling towers, was utilized at four southern California refineries and the Hyperion
