Tác nhân gây bệnh trong nước thải và Chất rắn sinh học GIỚI THIỆU Một tác nhân gây bệnh của con người là bất kỳ virus, vi sinh vật, hay chất có khả năng gây bệnh (Từ điển y tế Stedman, 1977). Theo định nghĩa này, vi khuẩn, ký sinh trùng, vi rút, chất vi sinh vật (endotoxins), nấm và các sinh vật khác gây bệnh. Hai loại chính là tác nhân gây bệnh tiểu học và trung học. Tác nhân gây bệnh tiểu học, như vi khuẩn, ký sinh trùng và vi rút có thể xâm nhập và lây nhiễm. | CHAPTER 7 Pathogens in Wastewater and Biosolids INTRODUCTION A human pathogen is any virus microorganism or substance capable of causing disease Stedman s Medical Dictionary 1977 . By this definition bacteria parasites viruses microbial substances endotoxins fungi and other organisms are pathogens. The two general categories are primary and secondary pathogens. Primary pathogens such as bacteria parasites and viruses can invade and infect healthy humans Burge and Millner 1980 . Secondary pathogens invade and infect a debilitated or an immunosuppressed individual. Often secondary pathogens such as fungi are termed opportunistic pathogens since they infect those who have suffered disease causing severe debilitation. Fecal coliform an indicator organism when present in large numbers indicates the potential presence of pathogens. Intestinal pathogenic bacteria normally react to environmental conditions in a similar manner as do coliforms. Thus fecal coliforms are good indicator organisms. Yanko 1988 demonstrated a strong correlation between fecal coliform densities and frequency of salmonella detection. The data showed that when the log fecal coliform density was below 3 1000 MPN g total solids the frequency of detection of salmonellae was in the range of 0 to 3 MPN g total solids. Yanko sampled biosolids compost and did not find salmonella in 86 measurements for which the fecal coliform densities were less than 1 000 MPN per gram. This was the basis for the pathogen regulations for Class A biosolids Farrell 1992 . One of the greatest concerns with land application of biosolids is the presence of pathogens for the following reasons Uptake by plants and entry into the food chain Movement through the soil and contamination of groundwater with potential contamination of drinking water Runoff and erosion containing pathogens and contaminating surface water. This could result in direct exposure to persons contacting the contaminated water . bathers or through .
