PV-Powered Biological Wastewater Treatment for Urban & Rural Applications

Abstract

This paper reports the second stage, and extensive water sampling procedures, of a study between the Centre of Renewable Energy and the Swire Institute of Marine Science (SWIMS) at HKU to set-up a safe, chemical-free, PV-powered wastewater recycling system for water conservation. A strategy for low-water use is required in a region where demand is rapidly rising due to massive development and increased use of domestic appliances leading to competition for riverhead access and depletion of water stocks. A decentralised, low-cost and low-maintenance recycling system has application to urban as well as rural sites in developed and developing countries. The HKU system combines artificial constructed ` wetlands' process, in which plants feed off the nutrients in the sewage, and ultra-violet (UV) light disinfection of the effluent before discharge. A standalone PV-array system composed of CIS ST40 modules, battery, charge controller and inverter supplies electricity for circulation pumps and the UV disinfection unit. The UV system has been compared with SWIMS' existing chlorine disinfection process against the various parameters set down in local and international irrigation water quality standards and is shown to deliver higher quality water without the toxicity of chlorination. A comparative study was made of the capital and operational costs of the two disinfection systems. The throughput, output values and the cost of each treatment stage have been evaluated and the disinfection process shown to have lower running costs.