The need to conserve water is becoming a common concern throughout the world. Whether this is due to the cost of water, availability of water, or environmental concerns, water conservation is becoming a major focal point, both in the public and private sector. In those areas where renewable water resources are limited, and in regions where there aresignificant environmental concerns and cost associated with wastewater discharges, reuse of wastewater may be a valid option to conserve valuable water resources and to reduce overall water-treatment cost.
The chemical process industries (CPI) represent a very significant portion of water use in the private sector. But in general, most of these facilities use a large amount of water for a variety ofpurposes including steam generation, cooling water, utility water, and so on.
As an example, for larger facilities, the need for fresh water can be 1,000, 5,000 or 10,000 gallons perminute (gpm), possibly higher. In addition, a significant amount of this water is returned to the environment in various water and wastewater streams which are treated to meet environmental discharge standards.This article examines water reuse in the CPI, with specific examples reuse in the CPI, with specific examples taken from the petroleum refining and petrochemical sectors.
Drivers to conserve water
There can be many reasons to reuse wastewater in petroleum refining and petrochemical plants. Many of these reasons are tied to the cost of fresh water and to environmental concerns.
A few of thechallenges many petroleum refining and petrochemical facilities must deal with are as follows:
*In many areas of the world, the costs of supplying fresh water can be very high due to the amount of infrastructure, such as pipelines and pumping stations, required to bring fresh water to facilities from remote locations
*Even though fresh water supplies may still be an economical solution for manyfacilities, the longterm viability of these supplies is in question in many locations throughout the world. As people become more aware of limited water supplies, whether groundwater or surface water, there is increased awareness that finding alternative sources of water for these facilities is an unavoidable issue that must be addressed
*At many facilities, fresh water is no longer available, or insuch short supply, that alternate sources of water (such as brackish water or seawater) must be used, thereby requiring much more sophisticated and expensive treatment systems to provide the desired water quality.
*The cost to treat water and wastewater discharged from facilities is a significant factor that must be evaluated anytime water reuse is considered. As more regions of the world becomeaware of the impacts of discharging pollutant – containing wastewater to the aquatic environment and the longterm effects of those pollutants, more emphasis is being placed on improving the quality of wastewater to be discharged. The list of potential pollutants being targeted is no longer constrained to organic pollutants, metals, biochemical–oxygen– demand (BOD), chemical – oxygen – demand (COD)and nitrogen compounds.
Considerations such as total dissolved solids and temperature of the wastewater are often included as parameters that must be addressed in discharges, eve to salt water environments
Whatever the reason, the availability, and associated cost of supplying water to petroleum refining and petrochemical facilities around the world continue to be growing issues. While onemay think that these concerns are limited to arid regions that traditionally have had an abundance of fresh water, such as Southeast Asia, North America, and Latin America, are now concerned with water availability.
These possibility to reuse wastewater generated within these facilities is now a viable alternative in many applications and geographies.