An Integrated Approach to water Pollution Control in Macau
Zhishi Wang，H. A. V. Basílio，S. K. Chan
Zhishi Wang(Faculty of Science and Technology University of Macau)H. A. V. Basílio(Governo de Macau, Gabinete da Central de Incineração e da Estação de Tratamento de Águas Residuais)S. K. Chan(Faculty of Science and Technology University of Macau)
Most of the world's coastal cities face a common problem in urban water management -- how to control worsening water pollution in urban areas and to protect aquatic ecosystems in coastal areas, which is a challenge for traditional technologies and methodologies, and leads to a radical change: from compartmentalising and isolating treatment to an integrated and ecologically sound strategy.
In this research we have attempted to apply the new and integrated approach to the case of Macau's water pollution control. Macau is a typi-cal coastal city in East Asia facing the problem of rapidly increasing pol-lution loading in the coastal area due to a sustained input of untreated urban wastewater and out-of-date urban water infrastructure facilities. A comprehensive pollution control program has been initiated by the Macau government including a new wastewater treatment plant and the rehabilitation of the existing drainage pipe systems.
In this paper, a framework for an integrated strategy is given and the present status and future trends of urban water pollution and coastal en-vironmental quality are reviewed. Technological schemes for urban wastewater treatment and marine disposal are discussed. A water resources conservation strategy is also discussed, focusing on the application of water recycling and reuse technologies to Macau.
Introduction
As clearly indicated in the document on the Directory Guideline of Macau Environment Act (Autorização Legistlativa (Lei n. 3/91/M)) approved by the Le-gislative Council of Macau in March 1993,1 a comprehensive policy is urgently needed for environmental protection of this territory, and the relevant action strat-egies to carry out this policy should be drawn up as soon as possible. This reflects a common concern of Macau society (government, public, business, industry, sci-entific institutes, etc.) about worsening environment quality (in coastal waters, urban air, land, physical environment, etc.) in this territory and an increasing awareness of the importance of keeping a harmonious relationship between envi-ronment and economy in any future development.
Macau is a coastal metropolis with a very high population density, experiencing a rapid economic growth and a post-urbanization period. Estuaries and coasts are generally complex environments, with great social, ecological, and economic impor-tance. Because of their multiple and sometimes conflicting uses, estuaries and coasts are often stressed beyond acceptable limits. Worldwide, many of these regions ex-hibit excess nutrients, low dissolved oxygen and high levels of organic chemicals, metals and disease-causing organisms.2 It is believed that such an aquatic ecological crisis has already occurred in Macau to some extent and will cause very serious con-sequences, such as irreversible damage to coastal regions surrounding Macau, if no immediate action is taken. The deterioration of water quality in coastal areas is mainly caused by water, air, and land pollution in urban areas, worsened by out-of-date urban infrastructure facilities (sewer and storm drainage systems, roads and trans-port systems, water supply systems, electric and energy supply systems, etc.), which is a common problem facing many metropolitan cities.3 Therefore, urban water pol-lution control through improvement of urban sewer systems and improving the qual-ity of the coastal sea water to restore the surrounding aquatic ecosystems are two priorities in Macau's environmental protection, and are urgent problems in the eco-nomic and social development of Macau, too.
An integrated and ecologically sound approach to water pollution control has been widely studied and adopted by most of the world's coastal metropolitan cities. The new concept has such dimensions as the balance between economic develop-ment and environmental protection, emphasizing incorporation of urban water pol-lution control into the overall development plan ot urban water infrastructure and the harmony between the urban ecosystem and the coastal aquatic ecosystem, focus-ing on improvement of sea water quality in the coastal area through control of the urban pollution sources.4 In this paper, an integrated and ecologically sound approach to Macau water pollution control including controlling urban water pollution sources and improving coastal water quality is discussed, and the relevant technological strat-egies are recommended. The major topics dealt with include:
Framework for Integrated and Ecologically Sound Strategies;
Present Status and Future Trends of Macau Water Pollution;
Integrated Management of Urban Wastewater;
Integrated Water Resource Conservation in Macau;
Conclusions and Recommendations.
This paper is part of the research results of a 92/93 graduate project study in the Civil Engineering Program of the Faculty of Science and Technology, Univer-sity of Macau with the help of the Gabinete da Central de Incineração e da Estação de Tratamento de Águas Residuais of Macau Government. The main aim of this research is to provide a scientific basis for the comprehensive water pollution con-trol program initiated by the Macau government, which includes a new wastewater treatment plant and the rehabilitation of existing urban drainage pipe systems.
Framework for Integrated and Ecologically Sound Strategies
The Ultimate Goal should be to pursue an environmentally sound develop-ment of the economy and society of this territory, i.e., the sustainable develop-ment, and environmental protection strategies should therefore be incorporated into the general development plan for the economy and society of Macau.
Specific Objectives are:
1) to restore the urban ecosystems of Macau (water, air, land and physical environment) and to control urban pollution in water, air and noise in the urban area by rehabilitation and re-building of the existing infrastructure facilities, par-ticularly the sewer pipe network and sewerage treatment systems;
2) to restore the aquatic ecosystems of the surrounding coastal areas by con-trolling pollution loading and mitigating water quality deterioration of coastal sea water; and
3) to assess environmental impacts of the large-scale coastal construction projects (new airport and new port), and to incorporate pollution control meas-ures into the projects' design and construction.
Principal Concepts are to adopt an integrated water management and eco-logical control strategy: i) integrated urban wastewater management; and ii) inte-grated water resources conservation. "integrated" means that
1) the urban wastewater management should be implemented both by building urban wastewater engineering systems and carrying out relevant administrative measures (e.g., implementing the "polluter pays" policy);
2) in the design and construction of the urban wastewater engineering system, wastewater collection, treatment and marine disposal must be considered integrally; and
3) water pollution control should be considered together with water resource conser-vation; wastewater management should cover the water supply as a whole.
"Ecologically sound" means that the urban wastewater treatment processes and technologies should echo the relevant ecological principles -- the thermody-namic principle, the principle of integration of the ecosystems of water, air and land, etc. The practice of urban wastewater management often ignores the mate-rial and energy thermodynamic principle which relies on "end-of-pipe" treatment instead of pollution source control. It is a resource-wasting practice. Another ex-ample is the unwise methodology of isolated wastewater treatment and purifica-tion while ignoring the linkage between water pollution and air and land pollu-tion. In fact, the terrestrial and aquatic ecosystems as well as the atmosphere are interrelated with each other, and a lot of pollutants in water come from land andair pollution. One of the reasons for the compartmentalized and isolated strategy is the traditonal thinking process that observes natural phenomena separately with-out considering their interrelationship.
Major Action to Be Taken should include:
1) making a comprehensive and systematic environmental quality assessment in this territory to identify the major water pollution sources in urban areas, to assess the impacts of urban water pollution on water quality and aquatic ecosys-tems of the surrounding coastal areas, and to estimate the effects of urban air pol-lution and urban refuse on water quality so as to set up water quality standards for urban pollution control and coastal aquatic environmental protection;
2) working out water pollution control technological strategies that must ad-equately echo natural laws, e.g., secondary thermodynamics and the intrinsic prop-erty of cycling material and energy in any ecosystem; they must therefore follow such principles as prevention of so-called "secondary pollution," making profits from pollution control by emphasizing material and energy cycling, "cleaner pro-duction," utilizing the natural purification capacity of the environment (e.g., the marine assimilative capacity for the discharged urban wastewater);
3) formulating and implementing economic and management measures as an important complement to engineering and technological measures which may in-volve the "polluter pays" policy and the "discharge permit" system as well as environmental economy and environmental resources management, initiating and coordinating public environmental education to upgrade citizens' environmental awareness and consciousness of obligation under the environmental regulations issued by the Macau government and the Macau legislative council.
Technological Alternatives For Urban Water Pollution Control should include:
1). integrated engineering design of wastewater collection, treatment and marine disposal systems and facilities, and specifically rehabilitation and re-build-ing of the existing urban sewer pipe system to upgrade its collection capacity for the centralized wastewater treatment plant to be built in Macau, determination of treatment processes suitable for urban wastewater quality standards, e.g., bio-chemical treatment technologies or physiochemical treatment methods, and de-sign of the treated wastewater marine disposal manner and facilities to be used to adequately utilize the self-purification capacity of the coastal sea waters;
2). application of water-saving technologies to save fresh water, which is criti-cally short in Macau, and in the meantime, application of wastewater reuse tech-nologies to the whole society and implementation of urban wastewater recycling and reuse strategies to reduce the pollution loading for the wastewater treatment plant and the coastal sea waters; and
3). control of air and land pollution sources related to water pollution, e.g., control of air dust pollution due to urban traffic and out-of-date road systems and surface run-off pollution mainly resulting from unwise refuse disposal.
Related Scientific and Technological Research Projects should be initiated and organized by the relevant departments of the Macau government, for which the government's function for coordination and supervision of the related scien-tific and technological research activities should be further emphasized.
The Related Research Topics may include:
a) laboratory and pilot studies in nutrient removal treatment processes (bio-logical and chemical) suitable for the Macau wastewater;
b) laboratory and pilot studies in wastewater treatment processes and fa-cilities for reuse, for which the related water quality standards for specific reuse objec-tives should be first defined;
c) environmental management planning for the urban development of Taipa and Coloane should be conducted and incorporated into the overall development plan for these islands.
Present Status and Future Trends of Macau Water Pollution
Water Quality Deterioration in the Coastal Areas
Macau is a coastal city with the highest population density in East Asia, experi-encing a rapid economic and trade development in recent years, which has exerted great pressure on the coastal sea waters so that their quality has critically deterio-rated. Data on sea water quality obtained in 1988 by a research team from the Zhuhai Environmental Protection Institute (in a collaborative research project between the University of Macau and the Institute)5 show that at present the major form of pollu-tion in the coastal areas is organic matter mainly from domestic wastewater pro-duced in the urban areas. Although most of the organic quality indices exceeded the relevant standards issued by China's National Environmental Agency, the organic pollution is still not as critical as expected at the present stage because the data for dissolved oxygen (DO) levels in most of the monitoring sites in that research showed that the DO level was still normal, ranging between 6 and 8 mg/1.
In addition to the obvious evidence of organic pollution in the coastal sea areas, there are two potential and long-term environmental risks that must be faced now: eutrophication of the coastal sea waters due to nutrient pollution input, and accumulation of heavy metals and other toxic species in the sediment which mainly come from industrial pollution and unwise urban refuse disposal. In this terri-tory, such potential environmental threats have not received full attention.6 These pollutants can irreversibly damage the coastal aquatic ecosystems so that control action must be taken immediately before it is too late.
According to the sea water quality standards (GB 3097-82) issued by National Marine Bureau of the PRC in 1982, sea water can be categorized into three types: Type I with COD7 of 3 mg/1 and DO8 of 5 mg/1; Type II with COD of 4 mg/1 and DO of 4 mg/1; and Type III with COD of 5 mg/1 and DO of 3 mg/1, among which Type I is the best. The monitoring data for the sea water quality in the area of the Macau peninsula can be collected as:
COD: 2.4 mg/1; DO: 6 mg/1,
which indicates that at least until 1988 the sea water quality of the coastal areas surrounding Macau was still good. However, even at that time the water quality index of oil, suspended solids, ammonia nitrogen and phenol had been measured as exceeding the quality standards.
The Laboratorio de Saúde de Pública, S. S. M. has been monitoring the water quality change of the coastal areas due to wastewater discharge. Based on recent measurement results obtained by the Laboratorio, the same conclusion as men-tioned above can be drawn.9
Urban Water Pollution Sources
Urban Sewage is the major pollution source in Macau. Particularly, domestic wastewater in the peninsula predominates in the public sewer systems, character-ized by a high concentration of organic matter rich in nutrient substances (e.g., ammonia nitrogen, used detergents) together with oil, a volatile suspended solid. Both the quantity and quality of the domestic wastewater are related to the popu-lation density of the residential areas. In the high-density region, the wastewater produced contains high concentrations of organic and nutrient matter and the wastewater flow rate is also high.
The monitoring data for the urban sewage water quality in the peninsula can be collected as:
COD: 203 mg/1; SS10: 75 mg/1; NH4-N11: 66 mg/1; NO3-N12: 0.2 mg/1; NO2-N13: 0.03 mg/1; TP14: 2 mg/1; Oil: 6.2 mg/1,which shows that it contains high concentrations of organic matter, which is typi-cal of a metropolitan city with a high population density.
Industrial and Commercial Pollution is also reflected in the urban sewage water quality monitoring. The relevant measured data for the domestic wastewater quality in Macau peninsula can be collected as:
Volatile Phenol: 0.17 mg/1; CN: 0.05 mg/l; Cr(VI): 0.013 mg/1; Pb: 0.01 mg/1;Cu: 0.01 mg/l; Mn: 0.01 mg/1; Zn: 0.02 mg/1.
According to the industrial wastewater quality standards issued by China's National Environmental Agency in 1985, some of the quality indices listed above more or less exceed the standards such as volatile phenol and lead and copper, which reflects the fact that the urban sewage contains a certain amount of indus-trial effluent and commercial wastewater.
It is estimated that the urban wastewater produced in Macau is 0.25 m3 each day per capita with pollutant loading of 90 g/capita.d. So the estimated pollution loading in the coastal areas surrounding Macau can be given as:
COD: 21 ton/d; SS: 8 ton/d; NH4-N: 7 ton/d; Phenol: 0.02 ton/d;CN: 0.005 ton/d; Oil: 0.62 ton/d; TP: 0.2 ton/d;
Pb: 0.001 ton/d; Cu: 0.001 ton/d; Mn: 0.001 ton/d; Zn: 0.002 ton/d.
So the total organic loading is about 36 tons per day and total heavy metals about 0.006 ton per day.
The daily average metal input into the coastal sea waters should receive criti-cal attention. According to the classical principles of aquatic surface chemistry, most metals put into the waters will attach to suspended particles in water and be transported together with these particles, ultimately to accumulate in the sedi-ment, which potentially threatens the aquatic ecosystems, particularly if once these accumulated or 'fixed' metals are re-mobilized under certain circumstances, greatamount of metals and toxic species go back to the sea water from the sediment with catastrophic consequences.
Urban Air Pollution and Surface Runoff15 are important sources of water pollution in Macau, which reflects the intrinsic nature of ecosystems in that water, air and land ecosystems are closely interrelated and pollution occurring in one will directly affect the others. It is believed that lead (Pb) pollution found in the coastal sea waters of Macau results from the urban air pollution due to exhaust emission gases from cars and trucks. The lead element with dust particles are emitted into the air and suspended there, and when rainfall occurs it is deposited onto the ground as rain droplets, and then with the surface runoff it comes to the sea, accumulated into the sediment. Other pollutions, such as suspended solids and metals can be caused by such a routine, too.
Environmental Carrying Capacities of the Coastal Areas
Because Macau is composed of one peninsula with an area of 6.7 km2 and two small islands (Taipa and Coloane), the territory's environmental carrying capac-ity is almost zero and the wastewater produced in the urban area cannot be as-similated to any extent in the land ecosystem; it can only be assimilated into the aquatic ecosystem. But the environmental carrying capacities, i.e., the capacities to assimilate the urban wastewater of the coastal areas, are quite different in dif-ferent places, depending upon the natural self-purification process of the sea wa-ters.
The so-called environmental carrying capacity of sea water can be defined as its capacity to assimilate the pollution loading produced in urban areas, particu-larly the capacity to assimilate organic pollution loading. So usually it can be esti-mated by the DO level in water. The higher the DO level, the higher the carrying capacity. In Macau the sea water DO level in most of the coastal areas is still nor-mal, which means that they still have some carrying capacities for urban wastewater input, particularly organic input. This advantage should be used for the marine wastewater disposal so as to reduce the cost of construction and op-eration of the wastewater treatment plant. The coastal area's carrying capacity also depends upon the area's dilution and diffusion conditions which are deter-mined by the flow pattern and velocity as well as tide patterns. It has been esti-mated, based on these hydraulic conditions in the coastal areas surrounding the peninsula, that the north-eastern area facing the main navigation channel of the Pearl River has a high carrying capacity and so it can be selected to be the receiv-ing region for urban wastewater disposal.
Integrated Management of Urban Wastewater16
Water, air and noise pollution control in the urban area of Macau is the key to environmental protection of the territory, which needs sooner or latersome urban infrastructure engineering projects to be carried out, such as the urban refuse incineration facility that has been built in Taipa and the wastewater treatment plant to be built in Macau. The following principles should be followed in engineering planning, financing, design and operation of this sort of projects. The first principle is so-called "comprehensive control strategy" design, i.e., designing to integrate instead of scattering control tech-nological schemes, based on the intrinsic interrelation of ecological and envi-ronmental aspects. Water pollution control should be considered together with air and land pollution. The second principle is the so-called "multiple techno-logical alternatives optimization" procedure, i.e., formulating several techni-cal alternatives for a certain control project and making a cost-benefit analy-sis for each of them to determine the optimal one to be carried out. Particu-larly, nature's self-purification capacity which the environment originally has should be fully considered in effort to save money.
Specifically for urban wastewater management in Macau, application of these principles can be understood as follows: to build the wastewater treatment plant is considered without doubt to be the key for water pollution control, and plan-ning and design of the treatment processes and facilities to be used in the plant are the main task. But equally important is to consider the drainage capacity of the existing sewer systems to collect and transport urban sewage and storm rain-water to the plant, as well as the water quality protection of the coastal area that is to be the body of water receiving the treated wastewater. Therefore, rehabilitation and rebuilding of the old sewer systems to upgrade their drainage capacities should be incorporated into the whole project design process, the sewerage marine dis-posal manner and place should also be determined at the same time, and the rel-evant engineering facilities should be carefully designed. Fully utilizing the sea's carrying capacity for assimilating organic matter from urban sewerage can sim-plify the wastewater treatment process to save money. But in order to avoid eutrophication occurring in the receiving coastal waters, nutrient control technolo-gies should be used in the treatment plant.
Pollution Control Technologies for Urban Wastewater Treatment
The traditional urban wastewater treatment is the "aerobic activated biologi-cal sludge treatment," which is designed for the removal of organic pollutants in wastewater. Because it is effective for purification of urban wastewater so as to be able to keep the dissolved oxygen level stable in receiving waters and also cheap and simple to operate, it is widely used in most coastal cities. But it has been found that this technology is not effective to remove nutrient pollution and heavy met-als in wastewater, which are two potential risks for the Macau coastal sea waters as mentioned above.
One problem that should be addressed in the design of the treatment proc-ess for wastewater purification is to prevent the coastal sea waters from eutrophication, which is usually a big problem for coastal cities. The organic materials introduced into the receiving waters by domestic sewerage usually containing twenty to one hundred milligrams of organic matter per litre, aresmall in comparison to the organic matter that can be bio-synthesized from introduced nutrient constituents (phosphorus and nitrogen). Generally, do-mestic wastes contain three to eight milligrams of phosphorus per litre, which can yield three hundred to eight hundred milligrams of organic matter per litre (i.e., algae). The aerobic activated sludge treatment with a heterotropic enrichment culture mineralizes a substantial fraction of bacterially oxidizable organic substances but is not capable of eliminating more than twenty to fifty per cent of nitrogen and phosphorus constituents. Therefore, the problem of eutrophication of the receiving waters cannot be effectively solved only by depending on the aerobic activated sludge method. Now a new generation of biological treatment technologies is emerging, which involves changing the aeration method in the existing biological treatment process to improve the capability of the process for removal of nitrogen and phosphorus, such as the AO method, which includes two stages of aeration: anaerobic and aerobic.
Another problem that we should be concerned with is how to control heavy metal pollution in domestic wastewater so as to prevent metals from accumulat-ing in the sediment. Again, the traditional biologically activated sludge treatment method is ineffective. The present practice is usually to carry out a "pollution source control" strategy and to remove these metal pollutants at the insource, particu-larly by applying material and energy conservation technologies.
Technological Alternatives for Wastewater Treatment Systems in the Macau Peninsula
Based on the pollution sources distribution in the urban area of the pe-ninsula and the environmental carrying capacities over the surrounding coastal water areas, three options for wastewater treatment schemes have been worked out:
-- the separate treatment scheme, in which the two treatment plants are built in the southeastern and northwestern urban regions, so that the plants are close to the pollution sources. The disadvantage of the scheme is that the treated wastewater from the northwestern plant must be transported a long distance for discharge into the northeastern coastal water area, which has the maximum environmental carrying capacity;
-- the centralized treatment scheme with the "secondary treatment" process to be utilized, in which the plant is built in the northeastern region of the penin-sula, and the wastewater produced from the northwestern region must be transported to the plant by a long main pipe; and
-- the centralized treatment scheme with the primary physical treatment proc-ess plus a designated marine sewage disposal outfall, which is a similar option to scheme 2. The only difference is that this scheme emphasizes utilization of the envi-ronmental carrying capacity of the receiving waters so as to save money.
Scheme 1 is the worst, so it is dropped. Which scheme 2 or 3 is better depends upon conditions such as the specific environmental requirements for water quality of the coastal waters and the financial conditions of the govern-ment.
The Macau Wastewater Treatment Plant17
The Macau Wastewater Treatment Plant, including a sludge treatment plant, is being constructed in the northeastern coastal region of the peninsula with a total investment of 33 million ptcs and a construction period of 24 months; in the meantime a comprehensive rebuilding of the peninsula urban drainage pipe system is proceeding with the construction of a peninsula-sur-rounding sewage-interception main pipe system as the central target. This construction project initiated by the Macau government is a combination of schemes 2 and 3 in which the secondary biological treatment and the marine outfall disposal measures will be adopted.
In the treatment plant that is being built in Macau, the second treatment system of the traditional activated sludge aeration is adopted in which removal of organic matter is the main task. The pollution control standards have been de-fined and issued by the Macau government, and include:
Biological Oxygen Demand (BOD): ................. 40 mg/l
Chemical Oxygen Demand (COD): .................. 150 mg/l
Suspended Solids (SS): .......................... 60 mg/l
Acidity (pH): .................................. 6-9
Oil and Grease: ................................. 15 mg/l
Detergent:........................................ 2 mg/l
It is planned to build three parallel treatment processes with the same tech-nology, with a total treatment capacity of 144,000 m3/d wastewater, which is the total discharge of the peninsula in 2010. Because the plant to be built near the residential area, it will be a closed system isolated from the surrounding environ-ment so as to prevent secondary pollution occurring; particularly noise and odor-ous gases, which will be controlled adequately. The attached sludge treatment plant includes two parts: sludge dewatering using pressure filtration and sludge incin-eration with a fluidized combustion bed. The maximum allowed gas emission for the sludge treatment has been defined as:
Dust: 100 mg/m3, HCl: 100 mg/m3, HF: 5 mg/m3, SO2:200 mg/m3, Heavy metal: 5 mg/m3.
The treated wastewater discharges into the northeastern area of the coastal sea with a 500 meter outfall pipe with diffusers at the pipe end.
Integrated Water Resources Conservation in Macau18
Macau society is facing two problems in water resource management:
1) Fresh water resources are permanently short so that Macau has to import raw water from Zhuhai, which leads to two potential problems: a) continuous increase in thecost with increased demand resulting from economic and population growth in Macau, as well as increases caused by inflation pressure in Zhuhai; and b) potential pollution of water so urces in Modaomen because of sustained industrial development and urbaniza-tion in the surrounding areas.
2) The quality of the coastal sea waters surrounding Macau is constantly deteriorat-ing due to permanent overloading of urban wastes (organic matter, nutrients and heavy metals) which mainly come from municipal wastewater produced every day. Because Macau is a small territory without any river or lake, its ecosystem has little carrying capacity to assimilate these wastes, which is further worsening the situation and overloading the aquatic ecosystem of the coastal areas.
Solving these problems requires a new strategy in the management of urban water resources. Up to now the water supply and sewerage treatment and disposal are still operated separately. More and more fresh raw water is purchased from Zhuhai to fulfil the increasing demand, while on the other hand more and more wastewater is produced by the increase in raw water supply and discharged into the sea, causing pollution. In order to protect the marine environment, wastewater treatment stand-ards must be sufficiently high to assimilate as much pollutant in wastewater as pos-sible within the treatment plant, which leads to high operating costs. Therefore, ap-plication of an urban water resource conservation strategy to Macau is urgently needed and will not only benefit the environment but the economy as well.
The central points of the water resource conservation strategy are to carry out a long term and comprehensive plan of wastewater reclamation and reuse as well as water recycling and saving, for which the related technologies, such as wastewater treatment for reuse or water saving technologies should first be studied, and the reuse objectives and standards should be defined. As for the wastewater reclamation system design, there are at least two alternatives: a large scale reclamation system to be built in the whole city including an advanced wastewater treatment plant and pipe systems for reused water; and small individual reclamation systems for differ-ent sectors and industries as well as residential areas with special reused water treat-ment facilities and distribution technologies suitable for each of the cases. These sys-tems can be used to reduce potable water supply and consumption and wastewater efflux into the sea, so that the amount of raw water purchased and wastewater load-ing on the treatment plant are both reduced.
Conclusion and Recommendation
1. Urban water pollution control is the key point of water resource manage-ment in Macau, aiming at meeting both human-designated needs and nature's re-quirement for water.
2. A water pollution control strategy should be integrated, which means that the technological measures must be complemented by administrative or manage-ment measures (e.g., wastewater discharge quality standard control, polluter-payspolicy, etc.); and that the technological strategy must be comprehensive, i.e., over-all control of wastewater production, collection, treatment, and marine disposal must be considered together.
3. A water pollution control strategy should be ecologically sound, which means that biological denitrification technology must be applied to the treatment of ur-ban wastewater to prevent eutrophication of the surrounding coastal waters, and the toxic species pollution sources must be controlled individually to prevent ac-cumulation in the sediment of the coastal waters; treated wastewater marine disposal facilities must also be designed carefully to fully utilize the environmental carrying capacity of the coastal waters to save money for construction and opera-tion of the wastewater treatment plants to be built.
4. Environmental planning for the development of Taipa and Coloane should be incorporated into the overall planning of the urbanization program for these islands.
Notes
1 Legislative Council of Macau, Directory Guideline of Macau Environment Act, Autorização Legislativa (Lei n. 3/91/M).
2 Zhishi Wang, "Tentative Action Strategy for Macau Environmental Protec-tion," Macau Daily News, March 28 -- April 5,1993.
3 World Resource Institute, World Resource 90/91, Oxford University Press, 1991.
4 Zhishi Wang, "Integrated Water Management -- An Ecologically Sound Ap-proach," International Conference on the Pearl River Estuary in the Surrounding Area of Macau, October, 1992.
5 S. K. Chan and Tan Weiguang, "Urban Development and Pollution in Macau," in D. Y. Yuan, Wong Hon Keong, and Libanio Martins (eds.), Population and City Growth in Macau (Macau: University of East Asia and Macau Census and Statistics Department, 1990) p. 231.
6 Lei Ka Hou and Zhishi Wang, "Guidelines of Water Environment Assess-ment of Macau," 92/93 Graduate Project Study in Faculty of Science and Technology, University of Macau, July 1993.
7 The water quality index -- COD (Chemical Oxygen Demand), an important index to measure the total organic matter in water including sea water; the higher the measured COD value, the more serious the contamination.
8 The water quality index -- DO (Dissolved Oxygen Level), which measures the oxygen content in waters including sea water; the higher the DO value the better the quality.
9 M. F. Ferreira, P. V. Ku, and W. Sun, "Influence of City Development on Wa-ter Source," Seminário Sobre Obras Públicas, Planeamento Urbano e Cooperação, Macau, 29 de Novembro a 2 de Dezembro de 1993.
10 Suspended solids in water which represents the particulate matter content in water or wastewater.
11 Ammonia Nitrogen in water indicating organic pollution level in waters.
12 Nitrate Nitrogen in water.
13 Nitrite nitrogen in water together with ammonia nitrogen and nitrate nitro-gen represent the total nitrogenous pollution in waters, which is a major nutrient pollution.
14 Total phosphate in water and other nutrient pollution in waters.
15 Chi-Leong Lam and Zhishi Wang, "An Integrated and Environmentally Sound Approach to Wastewater Management of Macau Peninsula," 92/93 gradu-ate project study in Faculty of Science and Technology, University of Macau, July 1993.
16 Ibid.
17 H. A. V. Basílio, "Preservação do Meio Ambiente em Macau," personal com-munication, October 1993.
18 Lai Weng Leong and Zhishi Wang, "An Integrated Approach to Water Resource Conservation in Macau," 92/93 graduate project study in Faculty of Science and Technology, University of Macau, July 1993. Also see Zhishi Wang, "Integrated and Ecologically Sound Water Management in Macau," Jornadas de Engenharia: Seminario de Macau -- 29/11 a 2/12 de 1993, November 1993.
