Wastewater and excreta use in agriculture in northern Vietnam : health risks and environmental impacts

Wastewater is commonly used in agriculture and aquaculture in developing countries but also in developed countries due to the growing water scarcity. In Vietnam, the use wastewater and excreta in agriculture has a long tradition. While this practice has clear advantages (fertiliser, economic impacts etc.), it harbours potential risks for health and environment. The aim of the thesis was to understand the health and environmental risks related to wastewater and excreta reuse in an agricultural community in Northern Vietnam, with a focus on intestinal parasitic infections and diarrhoeal diseases and nutrients flow. This work is to optimizing the benefit of wastewater and excreta reuse in agriculture in from health and environmental perspective, which allows proposing potential interventions for health and environmental improvement. Methods In the study area - 2 communes of Hoang Tay and Nhat Tan in Hanam province, Northern Vietnam - wastewater (i.e. Nhue River and local pond), human and animal excreta are commonly used as water irrigation and fertilisers: (i) Cross-sectional, cohort and nested case-control studies were conducted to assess the relative importance of exposure to wastewater and excreta for parasitic infection and diarrhoeal episodes. Exposure data were obtained from household and individual interviews. Stool examinations were used to assess infection status. (ii) Quantitative microbial risk assessment (QMRA) of Escherichia coli, Giardia lamblia and Cryptosporidium parvum infection due to the exposure to wastewater and excreta was conducted using multi-trial Monte Carlo simulations to estimate diarrhoeal risks. (iii) Material flow analysis (MFA) was used to analyse nitrogen (N) and phosphorus (P) flows in the environmental sanitation and agricultural systems. Results Helminth infections were prevalent (e.g. Ascaris lumbricoides 24%, Trichuris trichiura 40%, and any helminth infections 47%). Risk of infection increased for people having direct contact with Nhue River water (OR = 2.1, 95% CI 1.4-3.2), and using human excreta as fertiliser (OR = 1.5, 95% CI 1.0-2.3). Tap water use in household was a protective factor against T. trichiura infection (OR = 0.6, 95% CI 0.4-0.9). Entamoeba histolytica infection was not associated with contact with Nhue River and pond water, and human and animal excreta, but with close contact with domestic animals (OR = 5.9, 95% CI 1.9-18.9), never or rarely washed hands with soap (OR = 3.4, 95% CI 1.1-10.0) and average socioeconomic ststus (OR = 4.3, 95% CI 1.3-14.0). Diarrhoeal incidence in adults was 0.28 episodes per person per year (pppy). The direct contact with water from the Nhue River (OR = 2.4, 95% CI 1.2-4.7) and local ponds (OR = 2.3, 95% CI 1.3-4.3), handling practices of human excreta (OR = 5.4, 95% CI 1.4-21.1), and animal excreta (OR = 3.3, 95% CI 1.8-6.0) as fertilisers were important risk factors for diarrhoeal diseases. Furthermore, inadequate use of protective measures (OR = 6.9, 95% CI 3.5-13.9), close contact with people having diarrhoea (OR = 3.7, 95% CI 1.4-10.3), never or rarely washed hands with soap (OR = 3.3, 95% CI 1.8-6.3), eating raw vegetables the day before (OR = 2.4, 95% CI 1.2-4-6), and rainwater use in household for drinking (OR = 5.4, 95% CI 2.4-12.1) were also associated with increased the risks of diarrhoeal diseases. QMRA revealed that the most hazardous exposures included direct contact with Nhue River, local pond and field water, household sewage, and composted excreta. The annual infection risks due to exposure to wastewater exceeded the WHO reference level (10-4, i.e. ? 1 infection per 10,000 individuals), e.g. in scenario of growing rice, G. lamblia caused an infection risk of 0.75, C. parvum (0.39), and E. coli (0.96). The annual diarrhoeal risks were much greater than the WHO threshold values of 10-3 (i.e. 0.001 pppy), e.g. due to G. lamblia (0.50), C. parvum (0.15) and DEC (0.24) in scenario of growing rice. MFA simulations highlighted that the sanitation system is an important source of nutrients entering the surface water. Every year, 109 tonnes of N and 35 tonnes of P (75% N and 65% P from on-site sanitation system effluents) are discharged into the drainage system; and 118 tonnes of N and 25 tonnes of P released into surface water. Furthermore, simulations revealed that if nutrient management is not improved, levels of nutrients due to wastewater, faecal sludge, and organic solid waste will double until 2020. Conclusions In the agricultural settings, where wastewater and excreta are commonly used, important health and environmental impacts were documented. For mitigation purposes, personal hygiene practices and safe water and food consumption must be further addressed. Adequate on-site sanitation system technologies are warranted to assure waste treament and reduce nutrients discharge to the environment. Further investments in this direction are warranted to improve benefit-risk ratio for the agricultural community and increase sustainability of this agricultural system

Optimal parameters of dynamic vibration absorber for linear damped rotary systems subjected to harmonic excitation

Dynamic vibration absorber (DVA) is a simple and effective device for vibration absorption used in many practical applications. Determination of suitable parameters for DVA is of significant importance to achieve high vibration reduction effectiveness. This paper presents a method to find the optimal parameters of a DVA attached to a linear damped rotary system excited by harmonic torque. To this end, a closed-form formula for the optimum tuning parameter is derived using the fixed-point theory based on an assumption that the damped rotary systems are lightly or moderately damped. The optimal damping ratio of DVA is found by solving a set of non-linear equations established by the Chebyshev's min-max criterion. The performance of the proposed optimal DVA is compared with that obtained by existing optimal solution in literature. It is shown that the proposed optimal parameters allow to obtain superior vibration suppression compared to existing optimal formula. Extended simulations are carried out to examine the performance of the optimally designed DVA and the sensitivity of the optimum parameters. The simulation results show that the improvement of the vibration performance on damped rotary system can be as much as 90% by using DVA

How do we sell the hygiene message? With dollars, dong or excreta?

In North and Central Vietnam it is common among farmers to use excreta from the family double vault composting latrine (DVC) as fertilizer in the fields. The official Vietnamese health guidelines stipulate a six-month period of composting before applying excreta to two of their three annual crops. However, farmers in this region cannot afford to follow these guidelines and this paper presents the reasons why

Understanding food safety awareness and practices along smallholder pig value chains in Vietnam using participatory approaches

Pig production plays an important role in both food supply and economic development in Vietnam. We assessed the food safety awareness and practice of involved key actors along the smallholder pig value chains in Hung Yen, Vietnam using participatory approaches. Data collection included quantitative (checklists, questionnaires) and qualitative (in-depth interviews and focus group discussions-FGD) tools and was done in three districts of Hung Yen. All survey tools were developed and pre-tested. Checklists (n=22) and questionnaires (n=12) followed random sampling procedures. The respondents for in-depth interviews (n=24) were randomly selected, while the participants for FGDs (n=5) were recruited by convenience. Data collection was done between January and June, 2013. Descriptive statistic was used for quantitative data, while content analysis was used for qualitative data. The outline for data collection for included groups and stakeholders (slaughterhouse workers, pork sellers, veterinary and public health staff, people living around slaughterhouses, pork consumers) was structured around food safety, diseases and health risks. Differences in what some groups found important or unsafe, based on their occupational priorities or labour focus were identified by using ranking tables and analysed accordingly. Analyses show that for slaughterhouse workers and pork sellers the food safety risks were highest and linked to lack of training, or relying only on “learning by doing” an experience provided by other workers or sellers. People living around slaughterhouses expressed concerns about health effects but also pointed out the advantages of their proximity to slaughterhouses, such as job opportunities and easy access to fresh pork. Pork consumer groups were more concerned about sensorial criteria (e.g. freshly looking, bright red colour) and expressed also some awareness on pork quality. Veterinary and public health staff emphasised the gap between existing legislation and food safety practices. Findings provide information on food safety awareness and practices along various actors and stakeholders. There is a need for improved standards, targeted training and collaborative mechanisms between veterinary and public health authorities to better manage the food production chain

Health and environmental impact of agricultural intensification: Translating Ecohealth program-derived knowledge into practice

International Development Research Centr

Ecohealth research to regionally address agriculture intensification impacts on health and the environment in Southeast Asia and China

Ecohealth Field Building Leadership Initiative is a regional operational research network in Southeast Asia and China that focuses on solving human health problems associated with agricultural intensification. FBLI has 3 focus areas, namely research, capacity building and knowledge translation. FBLI gathers researchers, policy makers, community members and other stakeholders from 4 focused countries (China, Indonesia, Thailand and Vietnam). Here we describe the operational research component that focuses on aspects of agriculture intensification on health and the environment including animal waste from pig production (Vietnam), dairy production (Indonesia), pesticide use in vegetable production (China), and health risks in rubber plantation (Thailand). Integrated approaches to the research component including survey, participatory and cross-cutting methods are discussed. The research results from Vietnam and Indonesia showed health and environmental impacts of manure management options, in particular the biogas system and turning waste to value. In Hanam of Vietnam, the health risks from biogas effluent reuse include E. coli infection (19–22% of population exposed) and G. lamblia infection (45–55% of population exposed). In Pangalengan, Indonesia, the Ecohealth approach was used to promote the production of medicinal worm and casting biofertilizer from cow manure as an environmentallyfriendly fertilizer alternative. In Chachoengsao Province of Thailand, key findings include evidences for higher risk of vectorborne diseases (dengue and chikungunya) in rubber plantation areas as well as higher microbial and heavy metal contamination of water and soil. In six villages of three townships in a County of Yunnan Province, China, issues identified were lack of farmer knowledge of pesticides, pesticide abuse, and ineffective policy to reduce pesticide abuse. Pesticide contamination was recorded from 6.1% to 12.7% of vegetables depending on sampling location in the field or market. The findings from 4 countries illustrate how Ecohealth research has been applied in health and agriculture and serve as basis for interventions for reduce health and environmental risks