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The Water Resources Agency (WRA), Ministry of Economic Affairs (MOEA) has predicted that the annual water demand in Taiwan will reach approximately 20 billion m³ by 2021. However, the present water supply is only 18 billion m³ per year. This means that an additional 2 billion m³ have to be developed in the next 17 years. The reuse of treated wastewater effluent from municipal wastewater treatment plants could be one target for the development of new water resources. The responsible government departments already have plans to construct public sewerage systems in order to improve the quality of life of the populace and protect the environment. The treated wastewater effluent from such municipal wastewater treatment plants could be a very stable and readily available secondary type of water resource, different from the traditional types of water resources. The major areas where reclaimed municipal wastewater can be used to replace traditional fresh water resources include agricultural and landscape irrigation, street cleaning, toilet flushing, secondary industrial reuse and environmental uses. However, necessary wastewater reclamation and reuse systems have not yet been established. The requirements for their establishment include water reuse guidelines and criteria, the elimination of health risks ensuring safe use, the determination of the wastewater treatment level appropriate for the reuse category, as well as the development and application of management systems reuse. An integrated system for water reuse would be of great benefit to us all by providing more efficient ways to utilise the water resources. [ABSTRACT FROM AUTHOR]

Previous research has shown that nitrogen from municipal wastewater could be eliminated by a biofilter system. In this study a system of combined pre-denitrification/nitrification biofilters was set up. It is to investigate the effect of the hydraulic loading and recycled ratio on nitrogen removal. The characteristics of bacterial activity atdifferent heights is discussed. The experiment shows that longer hydraulic loading would result in better total nitrogen removal. Total nitrogen removal might be not dependent on denitrification but nitrification. Hydraulic loading that affects nitrification might be due to the diffusion of NH3-N from the bulk solution to the inner biofilm. The recycling NO3-N could be completely eliminated in the anoxic biofilter. The operation with longer retention time (HRT of 12 hours) would result in inner denitrification in the aerobic biofilter. Biological activity could be determined by the distribution of bacteria. The specific rates of pollutant decomposition depend on biological activity and effective biological VSS. The effect of the recycled ratio on the nitrogen removal is significant. Total nitrogen removal rate and nitrogen type of effluent would be determined by recycle ratio. The operation at low recycled ratio would result in worse total nitrogen removal, but the NH3-N of effluent would be lower. The operation in higher recycle ratio would be opposite to low recycle ratio. [ABSTRACT FROM AUTHOR]