In the very first article we ran about the environmental cost of building an oil refinery we focussed on the air emmisions and how they will affect the environment. Today we focus on the effect of emmissions to water that will result from the construction of the refinery.
The principal sources of effluent discharge from a refinery are treated Industrial waste water from process labaratory and utilities, treated sanitary waste water, clean storm water and waste water during construction as a result of cleaning, fishing and dewatering activities
Industrial wastewater discharged from the production process will be treated in an industrial waste water treatment plant compliant with refinery standards. Ugandan national standards for discharge of effluents have been established to control industrial waste water discharge, however since the refinery is funded by the financial bodies, World Bank Standards will apply except for where the NEMA standards are the more stringent or where there is no World Bank Standard for a substance which is regulated by NEMA standards.
During the construction phase, water sources like Lake Albert or other surface water bodies may be polluted because of domestic waste, discharged water from the work camp, discharged oil and lost fuel from construction Equipment and transport facilities, contaminants carried by high wind and rain.
Flushing and hydro testing of pipeline, equipment, vessels or storage tanks will generate large quantity of waste water. During commissioning, discharged lost liquid contains crude oil or oily water overflowed tank bank will contaminate water source due to increase of hydro carbon in water.
During the operation phase, waste waters from refinery operation consist of cooling water, process water, sanitary sewage water and storm water. The quantity of waste waters generated and their characteristics depend of the proces configuration. Waste waters are treated in on site waste water treatment facilities and then discharged. The water and blow down streams from refinery operations can become contaminated with dissolved gases, dissolved and suspended solids and hydrocarbons.
Water can also become contaminated with dissolved gases in the process, compounds that could be toxic and or could give to water an unpleasant smell. Nearly all refinery processes have steam injection to enhance the distillation or separation processes. This leads to the production of sour water (containing ammonia, hydrogen sulphide and hydrocarbons). Sour water needs striping prior to further treatment or re use as wash water.
Depending on the prevailing climate, storm or rain water can also generate a significant effluent stream in refineries. Rainwater may come into contact with potentially oil polluted surfaces.
Some water emission parameters are the dissolved solids, suspended solids, total organic carbon, total nitrogen, total phosphorous, COD, BOD, H2S, NH3, oil, aromatics (BTEX), henols, heavy metals, temperature, conductivity, bacteria and fish toxicity. As a general guide, approximately 0.1 to 5m3 of waste water (process water, cooling water and sanitary waste water) per tonne of crude is generated when cooling water is recycled.
Those discharges will contaminate the water sources in the area if proper treatment measure before discharging is not conducted. Water sources that may be impacted by discharges are surface water such as rivers, lakes like Lake Albert and ground water due to land and soil contamination.
Measures may be taken to mitigate waste water pollution. Some of these measures include
- Re using as much as possible the cleaned waste water
- Applying techniques to reduce waste water generated within each specific process or activity by segregation of contaminated, low contaminated or non contaminated water streams and where possible drainage systems. This entails the complete system of fresh water supply, rainwater, sanitary water process water, boiler feed water, cooling water, ground water as well as effluent collection storage and various primary, secondary and tertiary waste water treatment systems.
- Segregation of “once through” cooling water from process effluent until after this has been treated
- Good housekeeping in operation and maintenance of refinery and upstream facilities
- Spill prevention and control
- Ensure design of WWT includes sufficient capacity to prevent toxic shock, loads to the biotreater e.g by the use of a buffer tank, diversion tank, oversized reactor, etc.
- Good process practices and housekeeping to prevent contamination of the waste water
- Design the relaible drainage system surrounding the construction area, this system is required to be open and block free
- Sewage and effluent treating system has to be designed properly in such a way as treated waste water then has to comply with Ugandan environmental and health standards.
Compiled from the Fostewheeler Report on Uganda’s oil refinery