tailieunhanh - ENCYCLOPEDIA OF ENVIRONMENTAL SCIENCE AND ENGINEERING - MUNICIPAL WASTEWATER

THÀNH PHỐ NƯỚC THẢI Xử lý nước thải là nguồn cung cấp nước chi tiêu của một cộng đồng. Bởi vì xâm nhập của nước ngầm vào khớp lỏng lẻo ống cống, lượng nước ngầm thường xuyên lớn hơn số lượng nước ban đầu tiêu thụ. Xử lý nước thải là nước khoảng 99,95% và 0,05% vật liệu phế thải. Một yếu hơn (nhiều pha loãng) nước thải kết quả từ lớn mức tiêu thụ nước vốn. Chất thải công nghiệp sẽ góp phần vào sức mạnh xử lý nước thải. Xử lý nước thải dòng chảy thay đổi theo thời. | MUNICIPAL WASTEWATER Sewage is the spent water supply of a community. Because of infiltration of groundwater into loose sewer pipe joints the quantity of groundwater is frequently greater than the quantity of water initially consumed. Sewage is about water and waste material. A weaker more dilute sewage results from greater per capital water consumption. Industrial wastes will contribute to sewage strength. Sewage flow varies with time of day and will be higher during daylight hours. Larger cities will exhibit less variation with time than smaller cities. Many small communities will have a flow in the late night hours that is due almost entirely to infiltration. Per capita production will vary from less than 100 gallons per day for a strictly residential community to about 300 gallons per day for a highly industrialized area. The concept of population equivalent is frequently applied in evaluating industrial waste contributions to sewage flow and planning for hydraulic solids and biochemical oxygen demand loadings. Wastewater treatment facilities have high initial capital costs due to the need for large tanks equipment and land area. The designed life of a treatment plant is normally equal to the life of the bonded indebtedness of the project. It is expected that capacity will be just reached at the end of this period. In a community with combined sanitary and storm sewers it is often found necessary to bypass wastewater flows during periods of heavy rain or in low lying areas during high tides. Excess water may be held in detention basins until normal flow resumes and then treated in the plant. Bypassed flow can be screened and chlorinated before discharge. This subject is receiving increasingly close attention. Strength of sewage is usually expressed in terms of the following parameters total solids sometimes called volatile suspended solids VSS filterable solids and biochemical oxygen demand BOD . Many methods are available for determination of the .