Sustainable wastewater treatment for reuse and materials recovery through engineered chitosan materials.
In Qatar wastewater is generated from household, industrial and commercial use of desalinated water. The wastewater is then treated in sewage treatment plants for further use. The treated sewage effluent (TSE) is being used for landscape irrigation, make-up water for district cooling, aquifer recharge, some excess TSE is stored in a reservoir and some is discharged to the sea. TSE generation has increased more than 3.5 times over the past seven years, and it is estimated that the surplus would reach 77 million m3 per year by 2030 [1, 2]. Currently in Qatar, the generation of TSE is exceeding 500,000m3 per year and rising, the majority of which is not directly utilised. In addition, to the huge water availability potential from TSE in Qatar, an enormous amount of “produced water” is generated from the Oil and Gas industries. Between 3 and 4 barrels of “produced water” are generated for each barrel of oil. This supply of water is contaminated with several heavy metals, some hydrocarbons, other organics, inorganic anion salts and salinity [3-5]. Other applications need to be found and applied for the reuse of these wastewaters, after further treatment, and a number are under consideration, including: • Commercial carwashing Construction applications • Water for golf courses Concrete mixing • Water for athletic fields Process water • Street cleaning Boiler feedwater • Toilet flushing Firewater • Growing non-food crops Cooling water systems • Growing forage crops for cattle Equipment cleaning • Dust control • Recovery of phosphate and nitrate for fertilizer application • Produce better quality water for agricultural, landscaping, hydrophonics, and recharging aquifers applications The targeted uses of TSE are limited by several impurities including the presence phosphates, nitrates, metals, microorganisms and lower levels of pharmaceuticals – endocrine disrupting compounds (EDCs) and personal care products (PPCPs). The targeted uses of produced water in the Arabian Gulf are limited by a range of impurities also – metal ions (Ba, Cd, Li, Mn, Pb, Sb, Sr), organics (oil hydrocarbons and others), inorganic anions from boron, selenium, arsenic present as borates, selenates and arsenates depending on the pH) and salinity. 2.0 Project Description 2.1 General Description In my proposed project the chitosan based materials will be used to remove contaminants/recover value added materials from wastewaters. In Qatar, treated sewage effluent (TSE) is being reused in district cooling applications. The concentrated TSE containing nutrients (phosphates, nitrates) is discharged to the sea. There is a growing interest in reusing TSE for agriculture. There are evidences that PPCPs and EDCs, present in TSE, affect the plant growth and could contribute to toxicity. Other waste streams of Qatar include produced water and related water types from the Oil and Gas industries. The produced waters contain several metal ions and these wastewaters are a serious threat to environment when discharged into Sea. Overall, there is a huge potential for Qatar’s industries to recover high value added materials (such as phosphates, borates and nitrates AND strontium, lead, mercury, manganese, cadmium) and/or to remove contaminants to meet stringent environmental quality standards [6-10]. 2.2 Specific Research Steps and Targets In this PhD programme, two nanochitosans will be prepared and tested for their ability to remove: • Phosphate and nitrate in TSE; • BORATE IN DESALINATION WATER • Two organics from produced water in simulated produced water, MO AND MB ( DYE) • Problematic metals in simulated produced water; IRON • Heavy metals in real produced water. COPPER These operations will be studied using three process contacting systems: (i) Equilibrium tests to determine the adsorption capacities of the two adsorbents for the various pollutants in phases (i) to (vi). (ii) Batch adsorption rate tests to determine the kinetic and/or diffusion steps and the mechanisms of the adsorption steps for the various pollutants in phases (i) to (vi). Process variables will be investigated. (iii) Small pilot scale fixed bed studies to determine the breakthrough curves and the adsorption capacities for the pollutants shown in Phases (i) to (vi). Process variables will be investigated. Finally regeneration studies will be performed to assess if the two adsorbents can be regenerated and used again – several times. In addition, a preliminary assessment will be made to see if the recovered pollutants can also be reused or reprocessed.