DRY TOILETS FOR SUSTAINABLE SANITATION
IN RURAL AREAS OF NHUE-DAY RIVER BASIN

R. EMMERICH AND S. GROTHE

Institute of Geography, University of Greifswald, Makarenkostraße 22, 17487 Greifswald, Germany

Abstract: To provide the rural population with clean water and hygienic sanitation are central development goals of the Vietnamese government. This article presents outcomes from a household survey conducted in a typical craft village located in the Nhue-Day river basin. The focus of the presented study is put on toilet systems and their impact on the sanitary situation. Dry latrines and flushing toilets are subject to a profound comparison which is based on principles of sustainable water management and ecological sanitation. Flushing systems improve the hygienic sitation of households. Nevertheless, they cause trade-offs while putting a risk to the community and the environment, and jeopardise the achievement of the national clean water supply goal for rural areas. Consequently, flushing toilets are evaluated as unsustainable sanitary facilities. Dry toilets do not require water for their use and thus no sewer nor treatment system is required. Waterless solutions therefore are evaluated as sustainable sanitary facilities. Nevertheless, there is a discrepancy between positive effects on the environment and public community on one hand, and high preference of western style flushing toilets on the other hand. To overcome this contradiction the authors of this article suggest to internalise the negative externalities of flushing toilet systems based on the polluter-pays principle.

I. INTRODUCTION

Large investments are necessary to achieve the aims of the Millenium Development Goals. Main targets in the water supply and sanitation sector of Vietnam are to increase the number of rural population supplied with clean water and hygienic toilets [4,5]. The question is, how these goals are to be achieved in a sustainable way. For the Vietnamese government it is therefore critical to support solutions which are technically, socially, economically, and ecologically appropriate (see [8]). Unlike to western Europe the degree of canalisation also in densely populated rural areas is currently very low, and municipal wastewater treatment facilities are the exceptional case. Nevertheless, with economic transition flushing systems are on the rise as they promise clean and hygienic sanitation to the individual household (see [6]). The present study examines advantages and disadvantages of waterless latrines and flushing toilets in a sound comparison. Principles of a sustainable development of water management are therefore taken into account.

1. Sustainability

The term “sustainability” is subject to manifold and controversial discussions among scientists as well as politicians. According to the fundamental understanding of WCED [15] sustainability or sustainable development “implies meeting the needs of the present without compromising the ability of future generations to meet their own needs”. Sustainability can be described by criteria and indicators. Their application is of critical importance for the evaluation of existing water supply and sanitation systems. A sustainability evaluation of planned water management projects by such parameters should provide one basis for their subsequent realisation. Therefore criteria of sustainability have to recognise the interrelationship between ecological, economical, and social dimensions. Sustainability criteria which were developed for the macro-scale (see [1]) meet certain difficulties when they are applied to water supply and sanitation projects at local level. Thus, the presented study of domestic sanitary facilities is based on a set of principles developed by Kahlenborn and Kraemer [9] for the water management sector.

2. EcoSan

EcoSan (Ecological Sanitation) is a concept which aims for a sustainable development of domestic and municipal water supply and sanitation. The term ‘sanitation’ in this context means the hygienic disposal and recycling of (biogenic) waste and wastewater, and in a wider understanding hygienic health protection measures (see [18]). The prefix “ecological” stresses sanitation and wastewater management which is based on recycling systems. For Werner et al. [16] EcoSan is a practical approach to establish inter-sectoral resources management in the realisation of infrastructural tasks. The concept tends to close the loop of material flows following a holistic ecosystem approach. Connected with EcoSan thus is a paradigm shift in the waste and wastewater management from linear material flows (“end of pipe”) to material flow based recycling (“close the loop”). A central part of this consideration is the characterization of water, wastewater, and solid waste as nutrients, water, and energy. EcoSan is seen as an essential component of integrated water resource management (IWRM) [16]. The comparative evaluation of dry toilets and flushing toilets presented in this article therefore is based also on EcoSan principles as summarised by Winblad et al. [18].

3. Dry toilets

Dry toilets are waterless operated toilets with which excreta (faeces, urine) are collected. The national hygiene standard established by the Ministry of Health [10] distinguishes between double vault composting latrines and pit latrines with vent pipe. An additional type, which is not mentioned in this standard, is the ordinary pit latrine. From the process based point of view dry toilets can also be understood as composting toilets. However, the term ‘composting toilet’ means an aerobic collection and treatment system (see: [14]). Dry toilets are distinguished between excreta (faeces and urine) collecting systems and separation dry toilets which allow a detached treatment and re-use of faeces and urine [3].

4. Flushing toilets

Toilets designed for water-borne disposal and transport of human excreta are so-called pour flush or flushing toilets. The Vietnamese hygiene standard [10] distinguishes between pour flush latrines with compartment for excreta collection and septic tank latrines. Not mentioned in this standard are water flush toilets without compartment or septic tank, discharging human excreta directly into the environment. Generally, flushing toilets require a piped water supply to the flushing tank and produce wastewater (black water: mixture of excreta and toilet water) which requires sewer and treatment systems. From the material flow based point of view flushing toilets which dispose black water, and separating systems which dispose brown water (faeces and flushing water) and yellow water (urine and flushing water) can be distinguished [3]. Further versions are water saving toilets with decreased amounts of flushing water and vacuum toilets from which wastewater is transported in low-pressure pipes. The squat toilet is a widespread regional flushing toilet design in Asia.

II. METHODS AND MATERIALS

1. Household survey

In a typical craft village 320 households were interviewed during April and May 2007. The survey aimed to describe the socioeconomic situation and specify the state of domestic water supply and sanitation. The interviews put particular emphasis on information about the equipment of water supply infrastructure and sanitary facilities. The interview data was processed with SPSS statistical software. The investigation was carried out in Tống Xá village which is part of Yen Xa commune and located in Nam Dinh province. In 2006 Tống Xá had about 2,400 residents living in 550 households [12]. The main income source is agriculture (rice, peanuts, pig breeding etc.) as well as small and medium-sized casting production. In a close-by industrial zone about 50 companies are located. They engage approximately 500 people [12]. Further information was gained from the water supply company located in Lam town, which is the administrative centre of Y Yen district. For a detailed review of the socioeconomic conditions of Yen Xa commune and Tống Xá village in particular see Nguyen Thanh Lan et al. [12].

III. Results and Discussion

1. Domestic water supply and sanitation in Tống Xá vilage

In Tống Xá 62.2% of households (n = 320)¹ have a municipal tap water connection available. Other utilised water sources are near-surface groundwater (3-7 m below ground surface) and deep groundwater which is extracted from an aquifer at 40-60 m below ground surface. Another water source is rainwater which is collected and stored in cisterns. According to World Bank [19] municipal tap water, drilled well water, and rainwater can be considered as clean water sources in the Nhue-Day river basin.

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

¹ Number of cases alternates as not all parameter could be obtained from each household.

² Pearson χ²: 43.380, Phi: 0.369, n=318

³ Outlier adjusted

⁴ F: 8.276, t: 4.525

⁵ Pearson χ²: 16.400, Phi: -0.247, n=268

⁶ Poverty line for rural areas is 200,000 VND/capita/day according to Decision 170/2005/QD-TTg, General Statistics Office

55.7% of households are equipped with a flushing toilet, 43.4% use a dry toilet, and 2.5% of households have no own toilet available (n = 318). It was figured out a significant dependence between the availability of a municipal tap water connection and the use of flushing toilets.² Among households which use a pour flush toilet, 78.5% have a municipal tap water connection available (n = 177). The mean tap water consumption³ of households which are equipped with a flushing toilet is 70.1 litres/person/day (n = 114). It is significantly lower for households which are equipped with a dry toilet or have no toilet available (39.8 litres/person/day) (n = 46).⁴

In households which use a flushing toilet, 73.6% of latrines are connected to a septic tank (n = 87) and 13% to a biogas digester (n = 177). Households which run a biogas digester in all cases use a flushing toilet which is connected to the digester (n = 23). A significant relation was revealed between household income and sanitary facilities.⁵ Among non-poor households 65% are equipped with a flushing toilet, whereas only 40% of poor households⁶ have such a toilet available.

Figure 1. Dry toilets in Tống Xá: Simple pit latrine (left), double vault composting latrine (middle), opening for removal of latrine waste and urine separation (right).

2. Dry toilets and sanitation

Among interviewed households (n = 318) 43.4 % were equipped with a dry toilet. Only a few latrines met the national hygiene standard for sanitation [10]. Faecal compartments are not sealed, ventilation pipes are not installed. Nevertheless, most of dry toilets were completely enclosed and protected against storm water. Therefore water-borne emissions are considered irrelevant. Occasionally, double vault latrines were observed, sometimes equipped with sealing plugs. Typical dry toilets in Tống Xá have lateral openings for the removal of latrine waste (see Fig. 1). Sanitised faecal material is removed after a mean retention time of 2.7 months (n = 92) and used as fertiliser in agriculture. Also the recommended retention time is 6 months [17], Jensen et al. [8] notice that the addition of aggregates reduces the composting time. In Tống Xá ash, rice husks and straw are used as aggregates to enhance the composting process in dry toilets. Urine separation is practised also, it is used as fertiliser in the garden or on the field. Traditional, unsealed pit latrines are characterised by a low hygienic standard, faeces are exposed to insects and animals. Hand washing is not possible near the toilet.

Hygienic shortcomings of observed dry toilets can be corrected by technical upgrades pursuant to the national hygiene standard for toilets [10], improved handling of human excreta, and correct hand washing.

The installation, operation, and maintenance of waterless toilet systems are more cost effective than for flushing toilets. Both, piped water supply and pre-treatment system for black water are not required for the operation of dry latrines. Also water costs are lower for households which use municipal tap water.

Nevertheless, also wastewater without excreta (grey water) requires collection, controlled discharge, and treatment. But without black water production the municipal sewer and treatment systems can be designed much smaller and more cost effective (see [6]). Thus, costs for water management paid by the community decrease with an increasing number of households using waterless sanitary facilities. Though the operation and maintenance of dry toilets is based on expenditures and self-management of the individual user, the substitution of mineral and synthetic fertiliser by compost is highly beneficial especially for farmers.

3. Flushing toilets and sanitation

Taking into account that dry toilets traditionally are widespread in Vietnam (see [8]), the fact that 55.7% of interviewed households in Tống Xá use a flushing toilet reflects a remarkable change. This development is linked to the improvement of the income situation of households. Summarizing septic tank latrines and flushing toilets with biogas reactor as hygienic toilets in the understanding of the Vietnamese hygiene standard [10], approximately 41% of households in Tống Xá have a hygienic toilet available (Fig. 2). The sanitation goal of the National Target Program II (NTP II) for 2010 was not achieved yet in spring 2007. Accordingly 70% of households shall be supplied with hygienic toilets [4, 5].

One technical precondition for the operation of flushing systems is the piped supply of water. For most of cases (78.5%) municipal tap water is used for this purpose. Other households use groundwater. For this purpose it is pumped into a storage tank which is installed on the roof. From this cistern water is piped to the flushing tank. The use of flushing systems therefore is linked to the utilisation of piped water supply. It is one goal of the NTP II to supply 85% of rural population with clean water until 2010 [4, 5]. However, deep groundwater exploitation is connected with high investment costs for households. A sustainable utilisation of this resource, with other words, an extraction which does not exceed the groundwater recharge is not guaranteed [2]. Rainwater is not available all during the year and subject to industrial immissions [6]. About two third of households in Tống Xá were provided with municipal tap water in spring 2007. This water is extracted from the Day river and treated in a water work in Lam town. It is the most important clean water source for Tống Xá, but the capacity of the water work (2,000 m³/d) is limited.

The enhancement of the domestic sanitary situation in Tống Xá until recently has been driven mainly by a shift towards flushing toilets. Thus, the achievement of the NTP II goal for hygienic sanitation in Tống Xá is linked to increased tap water consumption. But, because clean water is a scarce resource in Tống Xá, it seems not reasonable that households use about 30-50% of supplied municipal tap water for toilet flushing while not all residents have this resource available.

Figure 2. Flushing toilets in Tống Xá: Typical western style toilet in bathroom (left), squat toilet in a piggery connected to a biogas digester (right).

Worth discussing is also the characterisation of pour flush toilets as ‘hygienic latrines’. It is not denied that flushing toilets improve the hygienic situation for the individual user. All the more if the piped water supply allows also hand washing immediately after using the toilet. However, the use of flushing toilets produces wastewater which is contaminated with human excreta. Whereas traditional dry toilets generate latrine waste which can be used for agriculture, the water-borne transport of human excreta creates a new material flow. The resulting black water contains a hygienic risk and may contaminate receiving water bodies. Therefore it requires a treatment in order to reduce human pathogenic faecal germs, oxygen reducing organics, and nutrient pollution. Generally such wastewater has to be transported out of the residential area and thus requires a sewer system. The sludge removal from septic tanks and biogas digesters is completely unregulated. Examined septic tanks did not have available an opening for sludge clearance. According to information from interviewed householders, they have to break the tiled ground of the bathroom to get access to the septic tank.

Untreated black water is discharged from 13.4% of flushing toilets in Tống Xá. The treatment effect of septic tanks is constituted mainly by the retention of solids for a couple of days, whereas biogas reactors provide a limited biological treatment. The effluents from septic tanks, biogas digesters, and black water discharged directly from flushing toilets are disposed uncontrolled. The toilet wastewater which is contaminated with human pathogenes runs off by a storm water drainage system flowing into the agricultural irrigation system. Proved faecal contamination in near-surface groundwater (E. coli exceeds limitation⁷ in 4 of 6 samples) and channel water (NH₄ + exceeds limitation⁸ in 11 of 13 samples) account for water-borne emissions of faecal material from flushing toilets in Tống Xá [13].

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

⁷ Clean water standard (MoH, 2005b)

⁸Surface water standard TCVN 5942:1995, level B

Near-surface groundwater, which is subject to faecal contamination by wastewater infiltration, is used by 54.1% of households (n = 290). Both, the exposure of black water in channels which run parallel to ways and streets, and the use of untreated wastewater for irrigation carry a certain risk.

4. Comparison of dry latrines and flushing toilets regarding their sustainability

In order to consider the requirements of a sustainable improvement of the sanitary situation, suitable technologies and management concepts have to be identified. Therefore dry latrines are contrasted with pour flush toilets in a profound comparison (see Tables 1 and 2).

For the purpose of comparison dry toilets are understood as waterless latrines pursuant to the national hygiene standard for sanitation [10]. Included are also waterless operated urine-separation toilets. Pour flush toilets and septic tank latrines according to the hygiene standard [10] are taken as the basis for the examination of flushing systems.

In the result dry toilets are the preferred sanitary system taking into account criterias of sustainable water management (see Table 1) and EcoSan principles (see Table 2). The advantage of dry toilets is the waterless operation, and the avoidance of complex technical solutions for water supply, black water discharge and treatment. Nutrients are recycled and do not get lost. The use of scarce clean water for the transport of human excreta is excluded. Nevertheless, in terms of acceptance flushing toilets have an advantage over waterless sanitary systems.

Table 1. Comparison of dry and flushing toilet systems according to principles of sustainable water management (see [9])

Principles of sustainable water management	Dry toilet	Evaluation	Evaluation	Flushing toilet ^1)without sewer and treatment system ^2)with sewer and treatment system
Regionality principle Water is a regional resource Avoidance of regional externalities Catchment area a reference frame for water management	- no water use - avoidance of water pollution	++	− − −	- water use and wastewater disposal - contamination of environment ^1) - wastewater contamination affects receiving water bodies and riparians^1), 2)
Polluter-pays principle Allocation of costs for water use and pollution to the polluter	- no water use (costs for toilet maintenance are allocated to the user)	+	+ −	- municipal tap water is charged with environmental fee - return of fee does not cover investment costs for sewer and treatment system
Avoidance of temporal and regional externalities	- no water use (water bodies are not utilised) - substitution of mineral/synthetic fertiliser	++	− −	- contamination of environment^1) - wastewater contamination affects receiving water bodies and riparians^1, 2)
Integration principle Holistic consideration of water cycle, interaction ecological and socioeconomic demands	- no water use - nutrient recycling, closed loop, substitution of mineral/synthetic fertiliser, improvement of agriculture soils	++	− −	- water use (clean water, wastewater) - trade-off: ‚clean water supply goal’ – ‚hygienic sanitation goal’
Overcoming the fragmentation of interests and accountability of users, service provider and administration	- management and maintenance is based on personal responsibility	+	−	- contradicting interests of users, service providers and administration
Cooperation and participation principle Consideration of all interests and public participation in water management decision-making	- decisions made on users own responsibility	+	−	- user dependence to water supplier (municipal tap water connection / supply) and administration (wastwater sewage and treatment)
Participation of user groups in water management activities	- participation of user groups (households) by own responsibilities in water management activities	+	−	- central water supply and disposal: detachment of user (household) from water supply and treatment and wastewater treatment
Cooperation and participation principle Consideration of all interests and public participation in water management decision-making	- decisions made on users own responsibility	+	−	- user dependence to water supplier (municipal tap water connection / supply) and administration (wastwater sewage and treatment)
Participation of user groups in water management activities	- participation of user groups (households) by own responsibilities in water management activities	+	−	- central water supply and disposal: division of user (household) from water supply and treatment and wastewater treatment
Minimisation of resource use principle Reduction of resource use and increased use of regenerative resources	- no water use - no energy consumption for operation and maintenance - nutrient recycling, substitution of mineral fertiliser (e.g. phosphorous)	+	− (−)	- water use (increased consumption of scarce clean water) - energy consumption for flush water supply (water transport) and for operation and maintenance of water treatment and pipe systems - energy consumption for wastewater disposal and treatment, and for operation and maintenance of sewer and wastewater treatment system
Precautionary principle Avoidance of measures with high potential of damage or risk	- contamination of agriculture soil and farming products, and water bodies with drug residuals - photolytic dissolution when compost is applied on top surface	(−)	−	- contamination of water bodies with drug residuals
Point of pollution principle Prevention of immissions at the place they emerge	- no wastewater generation	+	−	- generation of wastewater (blackwater)
Reversibility principle Consequences of measures in water management should be reversable as far as possible	- short to medium term achievement	+	− −	- after investment in tap water supply (water work, pipe system) and wastewater treatment (sewer network, treatment plant) medium to long-term system linkage - traditional habits and knowledge concerning the handling of human excreta and dry composting toilets get lost
Intergenerational principle Decision-making has to consider interests of future generations	- achieved	+	−	- present day decisions and investments for flushing / water-borne sewage systems affects future generation (approx. 25-50 years)

Table 2. Comparison of dry and flushing toilet systems according to principles
of ecological sanitary systems (see [18])

EcoSan principles	Dry toilet	Evaluation	Evaluation	Flushing toilet ^1)without sewer and treatment system ^2)with sewer and treatment system
Health protection	- sealed toilets do not allow contact between human excreta and insects, animals, storm water - minimum retention time for composting - no use of compost on vegetables and fruits for raw consumption	+ +	+ (+) − − − −	- no contact between human excreta and insects, animals, storm water - Limited sanitation by pre-treatment/digestion in septic tank or biogas reactor^2) - discharge of untreated or insufficiently treated wastewater (black water) to the environment and into water bodies - faecal contamination of water resources (near-surface groundwater, channel water, etc.) - possible contact to insects, animals, and humans - clean tap water used to transport and dilute human excreta; intensification of clean water scarcity
Environmental protection	- substitution of mineral/synthetic fertiliser, improvement of agriculture soils	+	− − −	- eutrophization of water bodies - energy consumption for flush water supply (water transport) and for operation and maintenance of water treatment and pipe systems - energy consumption for wastewater disposal and treatment, and for operation and maintenance of sewer and wastewater treatment system
Nutrient recycling	- nutrient recycling in closed loops	+	−	- nutrient loss due to linear material flows (nutrient discharge across catchment border)
Affordability	- low investment costs (no treatment system) - low operation and maintenance costs (no tap water demand, no treatment system operation) - self-management required/possible	+ +	− −	- costs for flush water supply (tap water connection, pipe system, tap water consumption, pumping) - costs for wastewater discharge and treatment (construction and O&M of sewer system and treatment facility)
Acceptance	- traditional toilet - simple pit latrines which do not meet hygiene standard (MoH 2005a) are widespread - modern dry toilets, which meet the hygiene standard (MoH 2005a) are rarely used	(+) (−)	+ (+)	- flushing toilets are preferred and mostly comply with hygiene standard [10] - flushing toilets have high popularity (clean, hygienic, modern, western life-style)
Convenience	- self-construction and installation possible - no blackwater discharge - piped water and connection to municipal sewage and treatment system are not required	+	−	- tap water connection or other piped water supply to flushing tank required - septic tank required - sewer required (household based and public) - wastewater treatment required (wastewater treatment facility, construction and O&M costs)

IV. Conclusions

The sanitary situation in Tống Xá has been subject to changes. Traditional dry toilets which do not meet the national hygiene standard have been substituted by flushing toilets. Due to the linkage between household income and flushing toilet use the regional economic growth is expected to cause increased use of such systems in future.

According to the comparison with dry toilets, flushing systems are figured out less or not sustainable, especially due to the required complex water supply, black water disposal and treatment. Nevertheless, flushing toilets are popular among residents, especially for households which have a higher income. At the first glance the use of pour flush toilets furthers the achievement of the national hygienic sanitation goal. However, it mainly improves the hygienic situation of the user whereas it compromises the hygienic situation of the community. The use of pour flush toilets is significantly linked with the supply of tap water which is required for flushing. Due to limited capacities of public water supply, an increased number of flushing toilets would limit the availability of clean tap water for all residents. Consequently, the achievement of the sanitary goal contradicts the clean water supply goal of NTP II.

Traditional simple dry pit latrines are no hygienic sanitary facilities. Nevertheless, dry toilets which meet the national hygiene standards may advance the achievement of NTP II hygienic sanitation goal. There is no trade-off between the national clean water supply and hygienic sanitation development goals.

Compared to flushing toilets waterless sanitary systems offer sustainable household sanitation. However, such toilets are not popular among residents. There are 2 options to resolve the contradiction between obvious advantages and the disaffection with dry toilets.

First of all the acceptance of dry toilets has to be increased by awareness rising, product marketing, and the provision of modern, western style desgins of waterless toilets.

Furthermore, the external effects of flushing systems have to be internalised based on the polluter-pays principle. Consequently, users of flushing toilets should be charged for the operation of such systems. Under the assumption of equal benefits in terms of the personal hygienic situation the advantages of dry toilets would prevail after allocating environmental costs. Such incentive is expected to increase the number of residents which choose a sustainable sanitary system.

Acknowledgement: The study was conducted in the frame of an IWRM project in Vietnam financed by the German Federal Ministry of Education and Research (BMBF: 02WM0765). All work in Tống Xá village was kindly supported by the Peoples Committee of Yen Xa commune and Nam Dinh Provincial Department of Science and Technology (DoST).

References

1. Blazejczak J. and Edler D., 2004. Nachhaltigkeitskriterien aus ökologischer, ökonomischer und sozialer Perspektive - Ein interdisziplinärer Ansatz. Vierteljahrshefte zur Wirtschaftsforschung, 73/1 : 10-30.

2. Doan Van Canh, Le Thi Lai, Hoang Van Hung, Nguyen Duc Roi, Nguyen Van Nghia, 2005. Groundwater resource of Nam Dinh Province. J. of Geology, B/25 : 31-42. Ha Noi.

3. DWA (German Water Association) (Ed.), 2008. Neuartige Sanitärsysteme. DWA-Themen, Hennef.

4. GoV (Government of Vietnam), 2006a. Sector Programme Support to Water, Sanitation and Hygiene Promotion. DANIDA, retrieved from www.danidadevforum.um.dk/NR/rdonlyres/0788AFEF-2A45-48F2-A538-1F16520D2B27/0/WSPS_II.pdf, 10 August 2009.

5. GoV (Government of Vietnam), 2006b. Decision No. 277/2006/QD-TTg approving the National Target Program on rural clean water and environmental sanitation in the 2006-2010 period. Signed by Prime Minister, Hà Nội.

6. Grothe S., R. Emmerich and J. Kasbohm, 2009. Sustainable municipal wastewater management for a craft village in Nhue-Day river basin. J. of Geology, B/34 (in print). Hà Nội.

7. GSO (General Statistics Office), 2005. Express News. GSO Website, http://www.gso.gov.vn/default_en.aspx?tabid=462&idmid=2&ItemID=2948 (accessed 26 September 2008).

8. Jensen P.K., Pham Duc Phuc, Dalsgaard A., Konradsen F., 2005. Successful sanitation promotion must recognise the use of latrine wastes in agriculture – the example of Vietnam. Perspectives, Bull. of the WHO, 83/11 : 873-874.

9. Kahlenborn W. and Kraemer R. A., 1999. Nachhaltige Wasserwirtschaft in Deutschland. Beiträge zur internationalen und Europäischen Umweltpolitik, 244 p., Springer, Berlin.

10. MoH (Ministry of Health), 2005a. Hygiene standard for various types of latrines. Decision of Minister of Health No. 08/205/QD-BYT 11/3/2005. Hà Nội.

11. MoH, 2005b. Hygiene standard for clean water. Decision of Minister of Health No. 09/2005/QD-BYT. Hà Nội.

12. Nguyen Thanh Lan, Nguyen Thi Thu Thuy, W. Steingrube, 2007. Review of socio-economic situation and spatial development planning by local authorities in Yên Xá commune, Ý Yên district, Nam Định province, Việt Nam. J. of Geology, B/29 : 76-84. Hà Nội.

13. Pavlik N., 2007. Untersuchungen zur Gewässereinschätzung in Siedlungsräumen der Provinz Nam Dinh/Vietnam. Mapping for Diploma thesis, unpublished.

14. US EPA (United States Environmental Protection Agency), 1999. Water efficiency technology fact sheet composting toilets. EPA 832-F-99-066, September 1999.

15. WCED (World Commission for Environment and Developement), 1987. Our Common Future. Oxford.

16. Werner C., Klingel F., Mang H.-P., Panesar A., Bracken P., 2003. Ecological Sanitation: Seine konzeptionelle Bedeutung für IWRM und seine Umsetzung in der Praxis. In: Werner et al. (Hrsg.): Closing the loop. Proc. of the 2nd Intern. Symp., 2.

17. WHO (World Health Organization), 2006. Excreta and greywater use in agriculture. WHO Guidelines for the safe use of wastewater, excreta and greywater, Vol. IV.

18. Winblad U., Simpson-Hébert M. (Eds.), 2004. Ecological sanitation – revised and enlarged edition. SEI, Stockholm, Sweden.

19. World Bank (Ed.), 2005. Regional Poverty Assessment Red River Delta Region. 2005.