Abstract: The present invention provides a multi-stage system for treating greywater comprising an electrochemical treatment module configured to carry out electrooxidation and electrocoagulation processes and a filtration module comprising a multistage filtration system for the treatment and removal of chemical and biological contaminants in greywater.

Abstract: A hydrogel battery includes a first compartment comprising a first electrode metal and a first hydrogel and a second compartment comprising a second electrode metal and a second hydrogel, and a background electrolyte (BGE) metal ion species. At least one of the first and second hydrogels selectively coordinates ions of the respective first and second electrode metals. The first hydrogel and the second hydrogel allow the BGE metal ion species to travel between the first and second compartments. A hydrogel battery may be implemented without a separator disposed between the first and second compartments, and may be rechargeable and/or flexible.