The waste water from hydraulic fracturing was treated using a physio-chemical process involving the precipitation and filtration of metal solids. Two waste streams are produced from this treatment process – liquid effluent and solid filter cake. The liquid effluent is tested to ensure it complies with the strict limits of the trade effluent consent, and then disposed of to foul sewer. It then undergoes further treatment at the sewage treatment works, prior to discharge. The filter cake is tested to determine if it is hazardous or non-hazardous, and then sent to a suitably permitted landfill site.