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ADVANCED ONSITE WASTEWATER SYSTEMS TECHNOLOGIES - CHAPTER 5

Tất cả các hệ thống xử lý nước thải tại chỗ cần một cơ chế xử lý nước thải phân tán và trở về với chu kỳ thủy văn. Dưới bề mặt phân tán (nonpoint nguồn thải) là cơ chế chủ yếu sử dụng cho phát hành nước thải từ hệ thống xử lý tại chỗ. Đối với hầu hết thế kỷ 20, lựa chọn nước thải tại chỗ đã được giới hạn để chỉ các hệ thống rác, do đó, sự lựa chọn quản lý đối với nước thải là một trong hai hệ thống thoát nước hoặc tự. | chapter five Effluent dispersal and recycling systems Introduction All onsite wastewater treatment systems need a mechanism for treated effluent to be dispersed and returned to the hydrologic cycle. Subsurface dispersal nonpoint source discharge is the primary mechanism used for releasing effluent from onsite treatment systems. For most of the 20th century onsite wastewater options were limited to only septic systems so the choice for wastewater management was either sewer or septic. One of the unintended adverse impacts of having limited onsite wastewater choices is devaluation or even condemnation of tracks of land for development when traditional municipal sewer systems are not accessible and soil and site conditions do not meet the regulatory requirements for septic systems. It is widely believed that the rules governing the operation of septic systems are used as de facto zoning tools mainly because if land is deemed unsuitable for installing a septic system i.e. no perc then no one can build a home or any other structure on it that has potential to generate wastewater. Research conducted and field experience obtained over the past several decades indicate that soil and site conditions necessary for treatment and ultimate dispersal of septic tank effluent are not necessary for the treatment and ultimate dispersal of secondary or better quality effluent. Hence we need to look at soil and site conditions in a totally different manner when advanced onsite wastewater systems are considered and soil and plant systems are used mainly for polishing secondary or better quality effluent rather than for reduction of organic waste load. This is the concept mentioned in Chapter 1 in which soil is not required to remove biological oxygen demand BOD or total suspended solids TSS and does not serve as a medium for mineralization of nitrogen from organic to inorganic forms. Instead those functions are performed by an advanced treatment system for which the conditions and the