tailieunhanh - Natural Wastewater Treatment Systems - Chapter 4

Thiết kế của hệ thống nước thải ao 4,1 XU HƯỚNG GIỚI THIỆU Thay đổi trong cách tiếp cận cơ bản để thiết kế các hệ thống ao trong 20 năm qua đã Been Chủ yếu giới hạn ở việc giới thiệu các phân vùng nổi nhựa để cải thiện các đặc điểm thủy lực của hệ thống ao, sửa đổi thiết kế cơ sở, và sự phát triển của một lựa chọn rộng lớn hơn hiệu quả hơn thiết bị sục khí. MỘT SỐ thay đổi kết hợp pha trộn một phần và hoàn thành hỗn hợp có Been phát. | 4 Design of Wastewater Pond Systems INTRODUCTION Trends Changes in the basic approach to the design of pond systems in the past 20 years have been limited primarily to the introduction of floating plastic partitions to improve the hydraulic characteristics of the pond system modifications to basic designs and the development of a wider selection of more efficient aeration equipment. Several modifications of complete mix and partial mix combinations have been developed and evaluated but the basic design concepts are unchanged. Examples of these modifications are the BIOLAC processes the Rich aerated lagoon design procedures and the LemTec biological treatment process. These among other modifications are described in this chapter. The importance of hydraulic characteristics was emphasized in the 1983 EPA lagoon design manual USEPA 1983 and has been restated numerous times in many publications however based on the number of pond systems constructed over the past 20 years with poor hydraulic characteristics one would assume that many designers have not read the literature or have ignored what they read. More recent designs have improved hydraulic designs considerably and it is hoped that this trend will continue. The trend toward omitting redundancy in the design of lagoon systems has been alarming. It appears that little thought is given to the need for maintenance in the future. Operating costs associated with aerated lagoon systems frequently have been ignored or overlooked in comparing options available to a community. The initial cost of systems without redundancy obviously is lower than that obtained with systems that include flexibility in operation but the cost to the environment and the owner will be far greater when maintenance is required. Several design procedures have been proposed and implemented since the 1983 design manual was written. Several have been applied some with great success and others with moderate success. Some of these .