Evaluation of the use of a graphite intercalation compound for the
development of a grey water recycling system by adsorption and electrochemical regeneration

Oki, R

Abstract

Grey water recycling has become of increasing interest as a water conservation method to help reduce the stress on water resources. This thesis evaluates the effectiveness of an innovative process in treating grey water for reuse for commercial and residential purposes as well as the possibility of heat recovery from the grey water. The process investigated is based on two fundamental elements; adsorption of contaminants onto a patented graphite intercalation compound (GIC) supplied under the trade name of Nyex™, and electrochemical regeneration of Nyex™ both taking place within a single unit.
The adsorption characteristics of Nyex™ was initially evaluated by conducting an adsorption isotherm and adsorption kinetics experimental study. Electrochemical regeneration of Nyex™ saturated with contaminants from grey water was also studied using an electrochemical cell. Results from this work has for the first time demonstrated that Nyex™ is only able to adsorb organic contaminants from grey water. The uptake of organic contaminants onto Nyex™ took place within a minute and the rate of adsorption was best described by the pseudo-second order adsorption kinetics. Adsorption isotherm curves illustrated multi-layer adsorption of organic contaminants onto Nyex™ with a monolayer adsorption capacity of 15 mg/g COD. An adsorption isotherm study conducted for anionic surfactant showed only monolayer arrangement of anionic surfactant molecules with a monolayer adsorption capacity of 0.3 mg/g.
Regeneration of the adsorbent is achieved by electrochemical oxidation in the anode compartment of an electrochemical cell. Complete regeneration of the adsorbent to its full adsorption capacity was achieved with a minimum charge of 22 C/g, and this capability was maintained over repeated regeneration cycles. A 4-log reduction in coliform through disinfection by free chlorine generated from the electro-chlorination process was observed, thus indicating that the system is highly effective at disinfection. A theoretical design of a drainage pipe heat recovery unit showed that it is possible to preheat mains water from 8°C to 25°C, using a heat exchanger coil of around 1 metre long. Evaluation of the operating cost as well as the cost savings from water and heat recovery suggests that this technology is economically viable and thus could be a major player in the grey water recycling market.

Citation

development of a grey water recycling system by adsorption and electrochemical regeneration. (Thesis). University of Salford

• Thesis Type: Thesis
• Acceptance Date: Oct 14, 2015
• Deposit Date: Jan 18, 2016
• Publicly Available Date: Jan 18, 2016
• Additional Information: Funders : Engineering and Physical Sciences Research Council (EPSRC)