Page - 91 - in Clean Water Using Solar and Wind - Outside the Power Grid

Used water treatment 91 is the dominating user or electrical energy (Lingsten et  al., 2011; Balmér,  2010). Assuming the high-end western European energy use of 45 kWh, each person would need an average power of 26 W over the year, similar to low-energy light bulbs. As an example, a small activated sludge plant for one household has been in operation in Sweden over the last year (Gillblad, 2018). A power supply of 60 W has been more than adequate, since most of this power is used for an UV lamp for disinfection. Compared with other uses the aeration energy requirement is small. However, aeration requires a continuous supply of electric power. This must be considered for solar and wind power supplies, so energy storage is important. Anaerobic treatment needs very little electric energy, mostly for some mixing of the sludge in the digester. This is an almost negligible energy use compared to other loads. Membrane separation needs electric power for the compressor delivering the pressure to the membrane process. As noted in Chapter 5.3, the required pressure depends on the pore size of the membranes. For micro- and ultra-filtration, the required pressure is much less than for reverse osmosis, so the necessary electric power input is much lower than for desalination (see Chapter 5.2 and 5.3). Disinfection using UV lamps is not an expensive energy user, as noted in Chapter 5.4. 7.4 FURTHER READING There are hundreds of books and a huge literature on used water (or wastewater) treatment. This book does not aim to be a textbook on water reclamation, but here are a few standard references: Grady et  al. (2011) give a comprehensive basis for the understanding of biological wastewater treatment. Metcalf and Eddy (2013) is a widely known standard textbook on wastewater treatment design and Asano et  al. (2007) is devoted to various methods for water reuse. Energy use in wastewater treatment is examined in the book Olsson (2015). Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user