GIS-BASED STARTING TOOLS OF DECISION MAKING FOR WASTEWATER TREATMENT PLANNING

NGUYỄN THỊ HỒNG¹, HORST WESSEL², JÖRG HARTLEIB³

¹Faculty of Geology, Hà Nội University of Sciences, Hà Nội, Việt Nam
²Moskito GIS GmbH, Mengeder Str. 623, 44359 Dortmund, Germany
³University of Greifswald, Jahn-Str. 16, Greifswald, Germany

Abstract: Since a past couple of years, the water resource quality in the medium-sized city of Nam Định Province located in the southeast of the Red River Delta in North Việt Nam is decreasing dramatically due to the strong industrial development, but still lacking sanitation infrastructure. On one hand waste-water from households, industrial zones, handicraft villages and other sources is currently drained untreatedly into the surface water, which is on the other hand, the main source of water supply to the city. In this study, the GIS software MOSKITO has been used as a tool for an Integrated Water Resources Management (IWRM) approach. It has the ability to process different types of input data and can be linked directly to EXCEL. IWRM includes a quite broad spectrum of issues. Here the issue of industrial waste-water treatment was chosen to demonstrate the functionality and the usefulness of such a tool.

I. INTRODUCTION

Water plays an important role in the socio-economic development of a territory as well as in its ecosystem. Although Việt Nam is relatively rich in water resources, the country is facing to a conflict between economic development and environmental pollution. Water shortage and water quality depression are critical problems which require more effort and specific actions to be taken [5, 6]. Nam Định, a province in the southeast coastal area of the Red River plain, is one example of this conflict. In recent years, the economy of Nam Định has grown strongly in both rural and urban areas. Traditional trade villages and seafood production in coastal areas are fast developed, but the waste-water is directly discharged into the environment without any treatment. The increasing amounts of inorganic fertilizers used in agriculture are another big potential threat to the surface and underground water resources. Beside that, the current situation of exploiting water without control and management has been destroying the natural structure of groundwater aquifers and degrading the quantity and quality of water resources [1].

The approach of an Integrated Water Resources Management (IWRM) was developed in order to give water related issues in an effective and sustainable way.

In Nam Định the conflict between different water users is quite strong and calls for good solutions. In the following, an IWRM approach is shown that is suitable for Nam Định province. The IWRM approach is supported by a Decision Support System (DSS) based on Geographic Information System (GIS), but also includes tools for the steps of planning and designing waste-water treatment plants. The tools work exemplarily for the trickling filter component for the treatment of industrial waste-water, especially water from the textile industry in Hòa Xá and An Xá industrial zones in Nam Định City.

II. METHODOLOGY

1. Decision Support System (DSS) and GIS

1.1. Decision support system: There are given several definitions for DSS but they all have in common that a DSS requires the use of computers and that it produces informations for decision makers.

According to Kjelds et al (1999), typical DSS interactive and integrated components are:

- Data and information management;

- Analysis and modelling;

- Scenario management and alternative formulation;

- Decision making.

Following the main idea of the DSS approach the following steps have to be fulfilled in order to be able to provide data and to support the decision makers in the field of sanitation and waste-water treatment:

1. Location of waste-water discharge points (industrial zones: list of companies, type of production, amount of wastewater, limit of discharge);

2. Classification of industrial waste-water according to type of production;

3. Identification of the type of pollution based on the type of production;

4. Waste-water amounts: estimation from production numbers;

5. Calculation of the total amount of waste-water to be treated;

6. Identification of treatment technologies required to treat identified types of waste-water;

7. Draft of technical concepts;

8. Cost estimation.

The above procedure does not include the selection of suitable locations for waste-water treatment facilities. Anyway this is an important step and during the decision process location and technology have to be reviewed several times in order to find the optimum solution (according to Förstner, 1993; Hosang & Bischof, 1998; Waste-water Ordinance (AbwV), 2004; German standard DIN 4261, 2006).

1.2. GIS and its applications: Developing a GIS application generally requires six typical steps (Fig. 1) Step No. 3 requires software development. Step No. 4 is highly recommended because it provides an opportunity to test the system design for a small pilot project area and fine-tune the design and computer programs, if necessary.

In case of Decision Support Systems (DSS) which are related to spatial data GIS are also applicable and are a very valuable tool in this context.

In this research, Moskito-GIS 5.0 system is used as the main tool to process and analyze spatial data in Nam Định City (Fig. 2).

Figure 1. Six typical steps for developing GIS application [3]

Figure 2. Planning process of GIS database (Source: Nguyễn T. H., 2009)

2. Estimation of costs for waste-water treatment facilities

Engineers and planners for waste-water treatment facilities are using cost models based on personal equivalents (PE) to estimate the expected investment. iaks GmbH has developed its tool based on projects between 500 and 500,000 PE. The tool estimates the costs for standard treatment technologies like activated sludge (AS) treatment and includes the investment costs for the sewer system and for the sludge treatment. For example a planned 400,000 PE unit has the following estimated costs in Europe:

Estimated costs for sewer system: ~ 76.7 million €

Estimated costs for sewage treatment: ~ 66.7 million €

Estimated costs for sludge treatment: ~ 8.4 million €.

Based on the project database of iaks GmbH the following equations can be found (iaks GmbH, 2009):

Estimated costs for sewer system: y = 4660 x ^-0.256

Estimated costs for sewage treatment: y = 3756 x ^-0.247

Estimated costs for sludge treatment: y = 434.18 x ^-0.237

The selected example is based on the German DWA regulations which requires the basins of about 100,000 m³ to be constructed by water-impermeable concrete (Imhoff, 2006). Therefore, the costs for basin construction already sum up to 2/3 of the estimated total costs.

Iaks GmbH has also developed a model to estimate the area demand of waste-water treatment (WWT) facilities using activated sludge technology:

Estimated area for AS-facilities: y = 12,353 ln(x) - 92,105

The data basis for the cost model of trickling filter (TF) facilities is much smaller. The following equation for the estimation of costs has been found:

Estimated costs for sewage treatment: y = 7931.1 x ^-0.396

III. RESULTS OF SELECTED WORKING STEPS

1. Geographic mapping and analysis

Until now GIS has not been applied in water management planning in Nam Định City by the local decision makers. Improvement of GIS, available GIS-maps as water management planning maps is considered quite helpful for planning and designing a WWT plant.

One of the first tasks during a GIS analysis is the transfer of all available data from the different software formats into one software version. The data are organized by differentiating them into layers with specific features: administration, hydrology, transportation, sewer system.

In the first step a decision maker should know details about the sources of waste-water in the project area, i.e. the quality and quantity of waste-water. Figure 3 shows a map of the textile industry currently operating in the industrial zones of Nam Định City.

Measurements of the waste-water quality in the two industrial zones show exceeded standard TCVN values for total P (up to 232 mg/l), COD (up to 2457 mg/l), SS (up to 80 mg/l), BOD5 and Total N. The maps (Figs. 4 and 5) show selected pollution parameter concentrations and amounts of waste-water in the two above industrial zones.

Figure 3. Textile industry in the industrial zones of Nam Định City
(Source: Nguyễn T. H., 2009).

Figure 4. Map of measured BOD concentrations in textile industrial waste-water in the industrial zones Hòa Xá and An Xá (Source: Nguyễn T. H., 2009).

Figure 5. Map of waste-water amount (textile) in Hòa Xá and An Xá industrials zone
(Source: Nguyễn T. H., 2009).

2. Cost estimations

According to this equation the WWT-facility of 400.000 PE using the trickling filter technology would require an investment of 19 million € which means only 1/3 of the costs for a comparable activated sludge plant. The costs for sewer system and sludge treatment are more or less the same for both technologies.

The area demand for trickling filters depends on the sizes of filter towers and machine hall. A rising PE-value increases the diameter and the heights of towers. Generally, the full facility requires less than 1 ha.

Based on the cost estimation database different scenarios are introduced and discussed.

Scenario A	Centralized Treatment Facilities at the two pumping stations Kênh Giá and Quán Chuột (This scenario represents the original idea of ND-authorities)
Water treatment	2 x 200,000 PE
Sludge treatment	Scenario A1: 2 x 200,000 PE
	Scenario A2: 1 x 400,000 PE
	incl. 10 km sludge pipes (100 USD/m = 1 million USD)

Table 1. Raw estimation of costs for scenario A for AS-T- and TF-technology

Activated Sludge Basin - technology for waste-water treatment (IAKS)
2 x 200,000 PE + 2x sludge	Cost for sewer system	Cost for water treatment system	Cost for sludge treatment system	Total costs
	96 million €	84 million €	10 million €	190 million €
2 x 200,000 PE + 1x sludge	97 million € (incl. pipes)	84 million €	8 million €	189 million €
Trickling Filter technology for waste-water treatment (GeoENcon)
2 x 200,000 PE + 2x sludge	Cost for channel system	Cost for water treatment system	Cost for sludge treatment system	Total costs
	96 million €	26 million €	10 million €	132 million €
2 x 200,000 PE + 1x sludge	97 million € (incl. pipes)	26 million €	8 million €	131 million €

Scenario B	Decentralized water treatment facilities & Centralized Sludge treatment (main idea of IWRM-group)
Water treatment	4 x 100,000 PE
Sludge treatment	1 x 400,000 PE
	& 40 km sludge pipes (100 USD/m = 4 million USD)

The above tables show that the investment costs for two waste-water treatment facilities are rather different for AS-technology with ~84 million € and TF-technology with ~26 million € (see Tab. 1). The reason for the strong difference are the additional costs for water-impermeable concrete (~34 million €) and aeration equipment in the AS solution. The difference between the two scenarios A1 and A2 are insignificant.

Table 2. Raw estimation of costs for scenario B for AS-T- and TF-technology

Activated Sludge Basin - technology for waste-water treatment (IAKS)
4 x 100,000 PE + 1x sludge	Cost for sewer system	Cost for water treatment system	Cost for sludge treatment system	Total costs
	112 million € (incl. pipes)	92 million €	8 million €	212 million €
Trickling Filter Technology for Waste-water Treatment (GeoENcon)
4 x 100,000 PE + 1x sludge	Cost for sewer system	Cost for water treatment system	Cost for sludge treatment system	Total costs
	112 million € (incl. pipes)	33 million €	8 million €	153 million €

Because of smaller units the total sum for each solution has increased by about 20 million €. The difference due to construction and equipment remains similar (Tab. 2).

The local stakeholders have to decide between the two technologies activated sludge (AS) and trickling filter (TF) as well as between the following alternatives: one central WWT facility (400,000 PE , 150 million €), two decentral WWT facilities (each 200,000 PE, 190 million €) or four decentral WWT facilities (each 100,000 PE, 210 million €). The costs for TF-technology would be ~60 million € lower. As the budget of the city is limited the construction of WWT facilities cannot be done in one project but has to be developed step by step.

Furthermore, the estimated costs for the sewer system need to be verified again as there is already some existing drainage system infrastructure.

Scenario C	Decentralized Water treatment facilities & Centralized Sludge treatment (demonstration of a small-sized unit for water treatment)
Water treatment	1 x 20,000 PE
Sludge treatment	No sludge treatment

In the case of new and fast growing residential quarters in Nam Định City the Scenario C provides a cost estimation. A waste-water treatment facility for 20,000 PE using AS technology would require 3 ha and 6.5 million € investment. In case of TF technology the are demand would be less than 1 ha and the investment is estimated at 3 million €.

IV. CONCLUSIONS

For a future GIS-based decision support system a typical dataset on industrial zones was prepared where data can be handled and processed by a combined GIS and EXCEL-tool. MOSKITO-GIS software is adopted as surface for this combined GIS & EXCEL-handling. The trickling filter technology is very suitable for Việt Nam due to its advantages regarding investment costs, area demand, operating costs and process controlling. The trickling filter technology for the first time creates an opportunity to develop mixed systems of decentralized and centralized concepts in urban areas like Nam Định City.

REFERENCES

1. Le Thi Lai, J. Kasbohm (Eds), 2007. Report of the Project "Integrated Water Resources Management (IWRM) and building model of waste-water treatment in Nam Định". Archives of Inst. of Geol. Sci., Hà Nội.

2. Mobius C.H., 2006. Waste-water of the paper and pulp industry - Load, lawful conditions, treatment. Wochenblatt Fur Papierfabrikation, 134/16 : 926-927.

3. Shamsi U.M., 2005. GIS tools for water, waste-water, and storm-water systems. ASCE Press, Reston, Virginia.

4. Sharifi M.A., W. van den Toorn et al., 2002. Application of GIS and multicriteria evaluation in locating sustainable boundary between the Tunari National Park and Cochabamba City (Bolivia). J. of Multi-Criteria Decision Analysis, 11 : 151-164.

5. Vietnamese Environment Protection Agency, 2006. Review of integrated water resources management (IWRM) in Việt Nam. Consultant report, V : 3. Hà Nội.

6. Vietnamese Environment Protection Agency, 2006. Wetland policies review in Vietnam. The Mekong Wetlands Biodiversity Conservation and Sustainable Use Program (MWBP). Consultant report, V : 9-14. Hà Nội.