Applied Environmental Microbiology Chapter 42 Applied Environmental Microbiology

Water Purification and Sanitary Analysis microbial containment candidates potential pathogens that can survive in water and represent severe health risks water purification critical link in controlling waterborne disease

Table 42.1

Water Purification… water held with high levels of suspended material  sedimentation basin large particles settle out partially clarified water mixed with chemicals such as alum and lime and  settling basin more material precipitates out in coagulation or flocculation process removes microbes, organic matter, toxic contaminants and suspended fine particles

Figure 42.1

Water Purification… water  rapid sand filters physically traps fine particles and flocs water treated with disinfectant chlorine concern about disinfection by-products (DBPs) such as trihalomethanes (THMs) which may be carcinogens ozone

Water Purification… EPA has developed regulations called the Long Term 2 Enhanced Surface Water Treatment Rule (LT2 rule) sets maximum containment level goal (MCLG) for specific pathogens health goals set at a level at which no known or anticipated adverse effects on health of persons occur and which allows an adequate margin on safety

Problem Microbes not consistently removed by coagulation, rapid sand filtration, and disinfection processes Giardia lamblia “backpackers disease” slow sand filters effectively remove Giardia cysts Cryptosporidium small protozoan with oocysts that escape usual purification schemes Cyclosporan protozoan that causes diarrhea viruses up to 99.9% are removed by usual purification schemes, but this not considered sufficient protection

Water Purification precise treatment depends on level of contamination but generally involves filtration techniques slow sand filters water passed over bed of sand with microbial layer (biofilm) cover the surface of each sand grain waterborne microbes are removed by adhesion to biofilm aeration and disinfection also used

Sanitary Analysis of Waters based on detecting indicator organisms indicate fecal contamination of water supplies indicate possible contamination by human pathogens

“Ideal” Indicator Organism suitable for analysis of all types of water present whenever enteric pathogens are present survives longer than hardiest enteric pathogen does not reproduce in contaminated water detected by highly specific test test easy to do and sensitive harmless to humans its level in water reflects degree of fecal pollution

Two Commonly Used Indicators coliforms fecal streptococci increasingly used to test brackish and marine water

Coliforms facultative anaerobic, gram-negative, nonsporing, rod-shaped bacteria that ferment lactose with gas formation within 48 hours at 35°C traditional method of detection is multiple-tube fermentation test

Figure 42.2

Other Tests for Indicator Organisms membrane filtration technique presence-absence (P-A) test defined substrate tests molecular analysis flow cytometry FISH quantitative PCRs microarrays

Membrane Filtration Technique water passed through filter  filter placed on surface of growth medium incubate count colonies used to detect total coliforms, fecal streptococci, and fecal coliforms from intestines of warm-blooded animals detected by incubation at 44.5°C

Table 42.2

Presence-Absence Test modification of MPN uses larger water sample (100 ml) sample added to lactose containing medium contains pH indicator to detect acid production based on assumption that no indicator organisms should be present in 100 ml of water detects total coliforms and fecal coliforms

Defined Substrate Tests tests for both total coliforms and E. coli; e.g., Colilert 100 ml sample added to medium containing ONPG and MUG produces a fluorescent product other indicator microorganisms are fecal enterococci used for brackish and fresh water

Figure 42.3

Wastewater Treatment number of steps that are spatially segregated decreases organic matter and number of microorganisms in human waste-impacted water has lead to major reduction in spread of pathogens

Table 42.3

Figure 42.4

Table 42.4

Wastewater Treatment Processes primary treatment removes solid material and forms sludge secondary treatment dissolved organic matter transformed into microbial biomass and carbon dioxide forms stable floc – settles well bulking sludge – does not settle properly activated sludge system horizontal flow of materials with recycling of sludge

Table 42.5

Figure 42.5

Wastewater Treatment Processes tricking filter waste effluent is passed over rocks or other solid materials upon which microbial biofilms have developed, and the community degrades the organic waste extended aeration reduces amount of sludge produced by using microbial biomass for energy requirements

Figure 42.6

Anaerobic Digestion often sludges from aerobic sewage treatment, together with materials settled out in primary treatment are further treated by anaerobic digestion reduces the amount of sludge for disposal produces methane

Table 42.6

Wastewater Treatment Processes… tertiary treatment removal of nitrogen and phosphorus that may promote eutrophication removes heavy metals, biodegradable organics, and remaining microbes, including microbes constructed wetlands employed in treatment of liquid wastes and for bioremediation

Figure 42.7

Home Treatment Systems groundwater water in gravel beds and fractured rocks below surface soil microbiological processes in groundwater are not well understood septic tanks for sewage frequently fail to work properly, contributing to groundwater contamination

Figure 42.8

Biodegradation and Bioremediation by Natural Communities metabolic activities of microbes can be exploited in natural environments where physical and nutritional conditions for growth cannot be controlled a largely unknown microbial community is present

Biodegradation and Bioremediation Processes examples use of microbial communities to carry out biodegradation, bioremediation, and environmental maintenance processes addition of microbes to soils or plants for the improvement of crop production

Biodegradation biodegradation has at least three definitions minor changes fragmentation mineralization

Figure 42.9

Bioremediation the use of microbes to transform toxic molecules to nontoxic degradation products the degradation of toxic molecules requires several stages, usually performed by different microbes reductive dehalogenation removal of a halogen substituent while at the same time adding electrons to the molecule usually occurs under anaerobic conditions

Figure 42.10

Fate of a Chemical in Nature structure and stereochemistry play critical role in predicting the fate of specific chemical meta effect occurs when constituent is in meta, as opposed to ortho position, the compound will be degraded at a slower rate many compounds added to environments are chiral possess asymmetry and handedness microbes often can degrade only one isomer of a substance; the other isomer will remain in the environment

Figure 42.11

Fate of a Chemical in Nature… microbial communities change their characteristics in response to addition of inorganic or organic chemicals acclimation occurs if chemical is repeatedly added, the community adapts and faster rates of degradation occur

Downside of Biodegradation can lead to widespread damages and financial losses if occurs in inappropriate situation or in an uncontrolled manner e.g., corrosion of metals, especially iron pipes, toxic degradation products

Figure 42.12

Stimulating Biodegradation bioremediation usually involves stimulating degradative activities of microbes already present at contaminated sites it is necessary to determine the limiting factors at the site (e.g., nitrogen or phosphorus or other nutrients) and supply them or modify the environment cometabolism addition of easily metabolized organic matter increases degradation of recalcitrant compounds that are not usually used as carbon or energy sources

Some Examples stimulation of hydrocarbon degradation in water and solids phytoremediation use of plants stimulation of bioleaching of metals from minerals

Figure 42.13

Figure 42.14

Bioaugmentation addition of microorganisms to complex microbial communities generally has resulted in only short-term increases in desired degradative activity outcome can be improved by providing protective microhabitats living microhabitats (e.g., surface of a seed, root, or leaf) inert microhabitats (e.g., microporous glass) natural attenuation use of natural microbial communities to carry out biodegradative process