The First Year's Operation of the Nimr Water Treatment Plant in Oman-Sustainable Produced Water Management using wetlands

Abstract

Abstract One of the largest industrial constructed wetland systems in the world was commissioned at the start of 2011 to sustainably manage more than 45,000 m3/day of produced water from the Nimr oilfields in Oman. This natural treatment system consists of a passive oil-water separator, 234 hectares of surface flow wetlands and 300 hectares of evaporation ponds and has been instrumental in reducing the amount of hydrocarbon polluted produced water being disposed to the deep well aquifers. The Nimr Water Treatment Plant (Nimr WTP), being a gravity flow system uses minimal fossil fuel for its operation and therefore results in an enormous saving in energy consumption compared to the conventional, energy-intensive disposal method of pumping the water more than 1.5 km below ground into deep aquifers under high pressure. Maximizing the use of locally available and naturally occurring materials for construction, treating and reusing oil contaminated soil from the oilfields and minimizing electricity consumption has decreased the carbon footprint, greenhouse gas emissions and environmental impacts of the oilfield, thus helping to protect people and the environment. The average operational power consumption for running the NWTP measured for 2011 was only 0.06 kWh per m3 of produced water treated, compared to 3.6 – 5.5 kWh/m3 for the deep well disposal that has traditionally been used. This equates to an energy saving of 98.3 – 98.9 % for managing the produced water and represents a huge saving in energy costs, fossil fuel consumption and subsequent green-house gas emissions making the project not only environmentally friendly but also economically successful for the oil producer. The reduction in CO2 emissions in 2011 was between 40,700 and 62,600 tons. The wetlands and ponds also provide a valuable habitat for migratory birds, with close to 100 different bird species having been identified at the site to date. During 2012, an extension to the wetland system (additional 120 hectares) is being constructed to increase the capacity of the plant to 95,000 m3/day. As part of this extension, approximately 167,000 m3 of oil contaminated soil has been biologically treated and reused as soil substrate in the wetland, providing additional environmental benefits. This paper discusses the details of the plant performance, data analysis and the challenges experienced in the first year operation of the Nimr WTP.