Xử lý sinh học là phương pháp được sử dụng rộng rãi nhất để loại bỏ, cũng như ổn định một phần hoặc toàn bộ các chất phân huỷ sinh học hiện diện trong chất thải nguồn. Thông thường, các chất phân hủy hữu cơ trong tự nhiên và có thể có mặt như bị đình chỉ, vật chất dạng keo hoặc giải thể. Các phần nhỏ của mỗi mẫu phụ thuộc vào bản chất của nước thải. Trong hoạt động của các cơ sở xử lý sinh học, các đặc tính của nước thải được đo về nhu cầu. | B BIOLOGICAL TREATMENT OF WASTEWATER 1. INTRODUCTION Biological treatment is the most widely used method for removal as well as partial or complete stabilization of biologically degradable substances present in waste-waters. Most often the degradable substances are organic in nature and may be present as suspended colloidal or dissolved matter. The fraction of each form depends on the nature of wastewater. In the operation of biological treatment facilities the characteristics of wastewater are measured in terms of its chemical oxygen demand COD biochemical oxygen demand BOD total organic carbon TOC and volatile suspended solids VSS concepts of which have been discussed Most of the conventional biological wastewater treatment processes are based on naturally occurring biological phenomena but are carried out at accelerated rates. These processes employ bacteria as the primary organisms however certain other microorganisms may also play an important role. Gates and Ghosh2 have presented the biological component system existing in the BOD process and it is shown in Figure 1. The degradation and stabilization of organic matter is accomplished by their use as food by bacteria and other microorganisms to produce protoplasm for new cells during the growth process. When a small number of microorganisms are inoculated into a bacteriological culture medium growth of bacteria with time follows a definite pattern as depicted in Figure 2 by plotting viable count and mass of bacteria against The population dynamics of bacteria in biological treatment processes depends upon various environmental factors including pH temperature type and concentration of substrate hydrogen acceptor availability and concentration of essential nutrients like nitrogen phosphorous sulfur etc. and essential minerals osmotic pressure toxicity of media or by-products and degree of In recent years cultures have been developed for biological treatment of many hard-to-degrade .
