Water Resources Planning Branch, WRA, MOEAWater Resources Planning Branch, WRA, MOEA

Project background and reason

Urban renewed water is an international trend. Advanced water recycle technology can be used to purify the discharge from the sewage treatment plant. The renewed water can be used as a regional water source. We conducted the renewed water trial project in 2007 and set up a discharge water renewed module (including sand filtration, ultraviolet sterilization, ultrafiltration membrane and reverse osmosis membrane unit) at the Futian Water Resources Recycling Center in Taichung to verify the feasibility of discharge renewed water from urban sewage treatment plants.

During 2009 to 2011, we took the Membrane Bioreactor (MBR) and the reverse electrodialysis procedure test. The biotoxicity test is performed on the fish and the murine chronic toxicity test to understand the impact of renewed water on aquatic organisms. To promote our research results, we published educational brochures and held workshops and courses to raise people’s confidence about renewed water.

The Major Events of The Renewed Water Trial Project of Futian Water Resources Recycling Center

Test results

1. The continuous operation test of the discharge water renewed module

   The module set up two sets of procedures: “Sand Filter(SF)-Ultraviolet light(UV)” and “Sand Filter(SF)-Ultrafiltration(UF)-Reverse Osmosis (RO)”, as shown in Figure 1 and 2. For more than three years of continuous operation test, the results showed that its operational efficiency and water quality were stable, and the water production could meet the tap water quality standards. After three years of long-term operation and regular on-line drug washing, the UF and RO systems were still stable.

   

   Figure.1 The process chart of “SF-UV ” and “SF-UF-RO”

   

   Figure.2 The discharge water renewed module

2. The Membrane Bioreactor treatment process test

   Membrane Bioreactor (MBR) combines all functions of the activated sludge tank, secondary sedimentation tank, sand filtration, ultrafiltration, and other units. It is a discharge water regeneration program that can be used in sewage treatment plants. The project has added a membrane bioreactor and tested for a sludge age of 60 days. The MBR procedure was used to reduce the sludge volume by at least 20 to 35%.

3. Electrodialysis Reversal treatment process test

   Adding Electrodialysis Reversal (EDR) test results show that the most efficient operating voltage is 84 volts, and the optimal circulating flow rate is 18 L/min. The higher the water yield, the higher the recycling rate, but the lower the salt removal rate (which is controlled at least 60% is a more acceptable value).

4. Water quality inspection and verification

   The "SF-UF-RO" program produces water that meets water quality standards. In addition to high salt removal and removal of dissolved organic matter, pathogenic bacteria (including fecal E. coli, Cryptosporidium, Giardia Lamblia, and Nematoda) were not detected, and the results of environmental hormones (Nonyl Phenol and Phthalates) were lower than the minimum detectable value. Further, the water quality test results were calculated for human health risks. The results showed that under normal operation, there was no carcinogenic risk and non-carcinogenic risk in RO water production, and there was no risk of microbial infection in UV and RO water production.

5. The fish chronic toxicity test

   The fish chronic toxicity test was conducted for 50 weeks. According to the statistical comparison, each serial dilution test group (100% renewed water, 2/3 renewed water + 1/3 tap water, 1/3 renewed water + 2/3 tap water, 100% tap water). The life span shows no significant difference among the groups. The liver, gill and germ glands were sectioned. The results showed that the tissue type of the group with higher proportions of renewed water was different from the lower group. It is presumed that it is related to the active release of ammonia nitrogen by the fish's body, but there are no significant differences in the life span.

6. The murine chronic toxicity test

   The murine chronic toxicity test was conducted for 90 days. The test groups, including 100% renewed water, 1/2 renewed water and 1/2 tap water mixed group, and 100% tap water group. After the mice were fed with different proportions of renewed water, there were no obvious lesions among the eyes, skin, organs, and appearance of the male and female surviving rats. In the tissue section, the small intestine, stomach, liver, kidney, heart, lung and reproductive organs were not found to have lesions or atrophy caused by drinking renewed water.

7. Long-term trial of renewed water

   The project cooperated with the Taichung Futian Water Resources Recycling Center and other organizations to provide renewed water to the manufacturers of the Central Taiwan Science Park(process water); the Taichung High Speed Rail (train cleaning water); the Dali Industrial Park sewage treatment plant (cooling system supplementary water); the Water Resources Planning Institute of Wufeng District (gardening water); and the Taichung Futian Water Resources Recycling Center (shaft seal and medicated water). Being tested for a long time, the pipelines were not corroded or scaled. It was accepted for use as cooling, car wash, watering, and medicinal water.

8. Educational promotion

   In the past three years, we have held up many education seminars and training tour guides of the module to explain the technical details of renewed water, and the number of visitors has exceeded 500. Interacted with the teachers of Shuyi elementary school and carried out several outdoor teaching activities to combine the concept of renewed water with natural science teaching. At the same time, we also cooperated with the National Museum of Natural Science to complete a film, and it was released at the theater of the museum.