Learning objective: to become familiar with: the behaviour of pathogens in the environment the effects of treatment strategies for minimizing the transmission of disease, especially in relation to agricultural use of excreta 3.3 Pathogen reduction How persistent are pathogens in the environment? How can we prevent exposure and disease transmission in sanitation systems? Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden collection Agricultural use treatment

Mexico: untreated wastewater gives 33% higher risk of diarrhoeal diseases (Cifuentes et al. 1998) Israel (kibbutz): partially treated stabilization pond effluent gives two-fold excess risk of enteric disease in 0-4 year-old age group (Fattal et al. 1986) No recorded incidents associated with ”appropriately treated” wastewater (Cooper & Olivieri 1998) National Research Council (NRC, USA, 2000) evaluated 23 studies: no proof for elevated or decreased risk when reusing sewage sludge Risk assessment a valuable tool Transmission of infectious disease during reuse Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Times given in days if not otherwise stated Estimated survival times for microorganisms in faeces, sludge, soil and on crop ( Faechem a 1983 and Kowan b 1985, in EPA 1999 )

Organism to be modelled4°C/low temp range20°C/high temp range E.coli*T 90 = daysT 90 = days Enterococci*T 90 = daysSame as 4°C BacteriophagesT 90 = daysT 90 = days Salmonella*T 90 = days EHEC*T 90 = daysSame as 4°C Rotavirusconservative model – no reduction T 90 = days T 90 = days GiardiaT 90 = daysT 90 = 5-50 days CryptosporidiumT 90 = daysT 90 = days AscarisT 90 = daysT 90 = days *Possible growth not taken into consideration Inactivation of microorganisms in faeces (Arnbjerg-Nielsen et al., 2005)

Organism group (ex.) Survival time Bacteria (Salmonella, E. coli)-Short (T 90 = days) Protozoa (Cryptosporidium)-Average (T 90 = ~1 month) Virus (rotavirus, bacteriophage)-Long (no reduction at 4°C, T 90 = ~ 1-2 months at 20°C) Factors that speed up die-off elevated pH (7 9, urea ammonia) higher temperature lower dilution Survival of microorganisms in human urine Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Time (days)

TemperatureLow temperature prolongs survival. Inactivation if >40°C, treatment processes 55-65°C. pH Neutral pH (7) suits organisms and their survival. Inactivation requires highly acidic or alkaline conditions. MoistureMoisture (e.g. in soil) favours the survival. Inactivation – if drying condition. Solar radiation/ UV-light Inactivation – by natural solar radiation or UV-lamps. Other microorganisms Pathogens survive longer in sterile water. Inactivation – through competition and by predation. AmmoniaOften affects microorganisms negatively. Inactivation – by ammonia produced at high pH. NutrientsNeeded for growth of bacteria. Inactivation – by lack of nutrients. Other factorsOxygen availability, chemical compounds. Parameters affecting microbial survival in the environment Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

(Esrey et al. 1998) Barriers required to prevent the spread of pathogens

We cannot only wait for the pathogens to be inactivated (eventual pathogen die-off) Measures can be taken to introduce conditions that are hostile to pathogen survival, such as High temperature, Low moisture, Competing microflora, High or low pH Ammonia gas etc. But, difficult to establish T 90 for reduction of each and every pathogen How can we kill pathogens? Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

ProcessBacteriaHelminthsVirusesCysts Primary sedimentation Plain Chemically assisted Activated sludge Bio filtration Aerated lagoon Oxidation ditch Disinfection Waste stabilization ponds Effluent storage reservoirs Large variations, depend on organism, difficult to predict Expected removal (log 10 ) of micro- organisms by wastewater treatment barrier Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Greywater treatment Treatment to remove grease, N, P, chemicals….and pathogens (see chapter 4) Choice of treatment method is dependent on the intended use Specific risks of use: Irrigation, subsurface Treatment in ponds – limit exposure Infiltration, drinking water Handling to avoid smell Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Faeces Urine Greywater Stormwater Industry Wastewater Sludge (Treated wastewater) Treated sludge Source- separation Wastewater treatment Sludge treatment Restrictions on usage Control/Regulations Sludge application Barriers to pathogens in sludge handling Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Will result in (compared to mixing of faeces and urine): Less smell Less volume (slower filling up, less to handle) Prevention of dispersal of pathogen-containing material (spilling, leaching) Safer and easier handling and use of excreta (volume, treatment) Less risk for disease transmission Urine diversion is therefore recommended Urine diversion in dry sanitation systems Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Primary treatment in dry toilet Adding drying material reduces pathogen load Storage Ambient conditions Biological methods Composting (heat, microbial competition, pH- changes) Anaerobic digestion (competition, pH-changes) Chemical treatment Alkaline treatment Ash, lime (pH-elevation and desiccation) Urea (ammonia) Incineration Treatment of faeces as barrier Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

The most appropriate treatment method (?) Other methods tried out in order to reduce the volume Easier handling for agricultural use Storage with low air exchange (tight containers) best method to keep the nutrients in urine Only necessary in large-scale systems Existing guidelines in module 3.4 Storage of urine Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Design of study: Ascaris and bacterio- phage (mimicks virus) added to the vault material Study the effect of changes in pH, temperature and moisture content 12 double-vault latrines were studied (of different design) (Carlander & Westrell 1999) Survival study – double-vault latrines in Vietnam Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Results: A total inactivation of Ascaris and the model virus (bacteriophage) was achieved within 6 months pH played a significant role for the inactivation of the bacterio- phages in the faecal material The inactivation of bacterio- phages and Ascaris was achieved through a combination of high pH ( ), high temperature (31-37°C) and low moisture level (24-55%)

Reduction of Salmonella typhimurium phage 28B in 12 latrines over time for different measures Carlander & Westrell, 1999

Reduction of Ascaris suum eggs (Carlander & Westrell 1999)

Inactivation of Giardia and Ascaris on coriander leaves Inactivation on crops Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

collection agricultural use treatment Closing the nutrient loop in a safe way Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Treatment as a barrier A combination of barriers to decrease exposure of humans to excreta should be applied in order to reduce risks for disease transmission in ecological sanitation systems. Treatment of the excreta is considered as a necessary step for the subsequent use as fertiliser on (agricultural) land. The goal is to significantly reduce risks – zero risk is not possible ”Minimise” risks (considering viable/practical/realistic measures) Insignificant amounts of pathogens No additional individuals diseased Treatment as a barrier (EcoSanRes, 2004) Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Incoming wastewater Wastewater effluent Sludge Reduction, die-off Concentration Dilution Wastewater treatment as a barrier Faeces Treatment steps = barriers Microorganisms reduced by 70-99,99% in STP (in Sweden) Treatment not optimised for pathogen removal Generally no regulations on outgoing (treated) wastewater Disinfection efficient method, but causes other problems Limiting exposure from outlet is important Sewage sludge – concentration of pathogens Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Primary treatment In the toilet (on-site) Some reduction of pathogens Reduce risks in subsequent handling Secondary treatment After finished collection Off-site or on-site (scale dependent) Significant reduction of pathogens Rendering the material ”safe” to use as fertiliser/soil improver Possibilities will be dependent on primary treatment Treatment of faeces Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Storage Ambient conditions Biological methods Composting (heat, microbial competition, pH- changes) Anaerobic digestion (heat, microbial competition, pH-changes) Chemical treatment Alkaline treatment Ash, lime (pH-elevation and desiccation) Urea (ammonia) Incineration Treatment of faeces (continued) Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

A total inactivation of Ascaris and the model virus (bacteriophage) was achieved within 6 months pH played a significant role in the inactivation of the bacteriophage in the faecal material The inactivation of the bacteriophage and Ascaris was achieved through a combination of high pH ( ), high temperature (31-37°C) and low moisture (24-55%) Conclusions from the Vietnam study Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

To prevent or decrease disease transmission Reduce number of pathogens Hinder actual exposure to the pathogen-containing material In analogy with different steps in e.g. drinking water treatment Health protection measures (WHO terminology) Technical, behavioural, medical, etc. Barriers of transmission Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden

Eventual pathogen die-off outside the body Persistence varies depending on type Bacteria may grow in the environment Helminth eggs have a latency period before they become infectious Natural conditions will affect rate of inactivation temperature, moisture, competing microflora, etc. Alter the conditions to increase the die-off rate temperature, pH, moisture, etc. But, difficult to state exact time-parameter limits for elimination of each and every pathogen Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden How can we kill pathogens?