Volume 4 | Issue 3 | 165 Adv Envi Was Mana Rec, 2021 Overview of Biological Treatment Technologies for Greywater Reuse Research Article Agricultural Engineering Department Faculty of Agriculture, Cairo University, Giza, Egypt A E Ghaly, E N Abdelrahman, R H Emam, N S Mahmoud, M M Ibrahim, E A Mostafa, M A Kassem and M H Hatem * Corresponding author Professor Abdelkader Ghaly, Agricultural Engineering Department, Faculty of Agriculture, Cairo University, Giza, Egypt Submitted: 09 Sep 2021; Accepted: 14 Sep 2021; Published: 30 Sep 2021 Abstract Greywater is a wastewater discharge originating from kitchen sinks, showers, baths, washing machines and dishwashers. Properly treated greywater can be recycled to meet global water shortages that is expected to afect 2.7 billion people around the world by 2025. Global water shortage can result in a reduction in agricultural land and increased dissertation leading to poverty, faming, war, illegal migration and human trafcking. Greywater contains fewer pathogens than domestic wastewater, is generally safer to handle and easier to treat and reuse onsite for toilet fushing, landscape and crop irrigation. Recycling of grey water provides substantial benefts for both the water supply system by reducing the demand for fresh clean water, and for the wastewater system by reducing the amount of wastewater required to be conveyed and disposed of. In this paper, the existing biological treatment systems for greywater are reviewed. These are: (a) constructed wet land, (b) sequencing batch reactor, (c) vertical fow bioreactor, (d) membrane bioreactor, (e) up-fow anaerobic sludge blanket, (f) rotating biological contractors, (g) trickling flters, (h) aerated lagoons, (i) anaerobic up-fow flter, and (j) expanded bed up-foe reactor. In a biological treatment, the degradation and transformation of greywater constituents are facilitated by the biochemical reactions carried out by microorganisms in the liquid medium. However, the efuent of biologically treated greywater may contain pathogenic microorganisms, requiring a fnal disinfection step to eliminate the risk of contracting pathogenic diseases. Selection criteria for a disinfectant include: (a) non-toxicity to humans, domesticated animals, and aquatic ecosystems, (b) low cost (c) easy handling, (d) reliable analysis, and (e) a satisfactory residual concentration. Any disinfection process selected (whether chemical oxidants or irradiation treatment is selected) should be evaluated taken into consideration the conditions of the wastewater source and existing biological treatment design. www.opastonline.com Citation: A E Ghaly, E N Abdelrahman, R H Emam, N S Mahmoud, M M Ibrahim, E A Mostafa, M A Kassem and M H Hatem (2021). Overview of Biological Treatment Technologies for Greywater Reuse. Adn Envi Was Mana Rec, 4 (3):165-191. Keywords: Water Shortage, Greywater, Biological Treatment, Degradation, Disinfection, Reuse ISSN: 2641-1784 Advance in Environmental Waste Management & Recycling Introduction Global water resources are worsening, and water shortages will afect 2.7 billion people by 2025 (about one third of the world population) [1]. This will result in a reduction in agricultural land and increased dissertation leading to poverty, faming, war, illegal migration and human trafcking. Reusing greywater can contrib- ute towards solving this water shortage problem. Greywater is a wastewater discharge originating from kitchen sinks, showers, baths, washing machines and dishwashers [2-6]. Table 1 shows the main sources of greywater and their constituents [1,7,8]. Greywater is diferent from domestic wastewater (wastewater from toilets) which is classifed as black water. As grey water con- tains fewer pathogens than domestic wastewater, it is generally safer to handle and easier to treat and reuse onsite for toilet fush- ing, landscape and crop irrigation and other non-potable uses [9- 16]. Recycling of grey water provides substantial benefts for (a) the water supply system, by reducing the demand for fresh clean water, and (b) the wastewater system, by reducing the amount of wastewater required to be conveyed and treated [17,18] thereby reducing energy use and chemical pollution associated with treat- ment and disposal [19]. Studies have shown that greywater use for irrigation or toilet fush- ing appears to be a safe practice and no additional burden of dis- ease being observed among greywater users irrigating their felds arid regions [20-21]. The aim of this study was to examine avail- able biological treatment technologies for greywater reuse and to review their efectiveness in removal of pollutants from greywater including pathogens.