The Characteristics Of Eutrophication In The Water Body Of Landscape Application By Reclaimed Water And Control Methods

As the development of the society, people need more and more landscape for entertainment. Presently one of the most important problems of landscape in north cities is lack of water resource. Using reclaimed water is a good method because of the steady water quality, economizing water resource and less pollution to environment. While reclaimed water belongs to eutrophication water, it has excessive nitrogen and phosphorous which lead to water bloom. So according to the characteristic of the eutrophication water, we should investigate an economic and simple technique to use reclaimed water in landscape.This study aims at the maintenance of landscape in Beijing during Olympic Games, and uses reclaimed water from the Gaobeidian wastewater plant as the water resource. According to the researches of the influencing factors of the eutrophication water, and the technique comparisons of ozone, coagulation and ultrafiltration, we can insure the best method is combination of ozone and ecosystem. The best maintenance object is the eutrophication water without water bloom. This method can control the algae growth and enhance self-purification. Using ozone and ecological combining technique can control algae growth, enhance self-purification and security of ecosystem. This maintenance technique will have more extensive application in reclaimed water landscape.Algae grow fast in reclaimed water landscape which contains massive algae, mainly in green algae. It can produce water bloom within five days. If the tap water has enough nutrition, it also can lead to water bloom, mainly in cyanobacteria. Algae can not grow in distilled water because of the lack of microelement although enough of nitrogen and phosphorous are present. The algae can normally grow in most cases except for the water pH is below 2 or above 11. When water bloom happens, the water pH rises to 9.5, and the self-regulation of algae can relieve the influent water pH. Algae can utilize alkalinity as carbon source, so high alkalinity is helpful to algae growth, and it can produce hydroxide ion which leads to high pH, so more carbon dioxide enter in water and it's better for photosynthesis. Phosphorous concentration is a limiting factor to algae growth, and the optimum range is 0.5~5 mg/L. The nitrate is more benefitial to algae growth than ammonia with high water pH.In the maintenance of reclaimed water landscape, ozone can inactivate 95% algae, but can't oxidize the algae cells completely. Ozone can improve the biodegradability, but can't remove the nitrogen and phosphorus directly. In the research, the contact reactor affects the efficiency of ozone, which is only 55% in bench scale experiment. Enhanced coagulation has good removal efficiency to algae and phosphorus, with the addition of 50 mg/L poly aluminium chloride and 1 mg/L permanganate composite chemicals. The algae removal efficiency is significant using coagulation technique for water bloom landscape and the water pH decrease rapidly, but a great deal of suspending flocculate appears and makes fishes dying. The ozone technique doesn't have fast effect to water bloom, but it can enhance the ecosystem and self-purification, and make the nitrogen and phosphorus decrease gradually. The landscape water treatment by ozone alone has not obvious effect expect of establishing aquatic ecosystem. In ecosystem, fishes can promote algae growth and more easily bringing water bloom. The content of chlorophyll can reach 1000mg/m3.Using ozone combined with ecological technique to eutrophication water without water bloom, the landscape has high transparence and algae growth nearly stops, even if the maintenance technique stopped. The water contains high nitrogen and phosphorus and little bacteria. The ecosystem is steady and the still water has high security. Alone ozone technique also has good effect but when the maintenance stops, algae appear fast and produce water bloom. Ultrafiltration has low effect and membrane flux is low after experiment, so ultrafiltration is not suitable for maintenance of landscape. Massive algae growth can absorb nutrition in water and transform nitrogen and phosphorus from inorganic conformation to organic conformation. With the ozone maintenance the organic matters in water is mainly hydrophilic intracellular amino acid and the molecular weight is 600~5000. The landscape of the blank sample contains more soluble organic which is mainly hydrophobic and its molecular weight is below 500. They are the main factors to membrane fouling. The coagulation technique has great effect to water quality and the ultrafiltration technique has the problem of membrane fouling, so they are not fit for maintenance technique of reclaimed water landscape. We use ozone combined with ecological technique for engineering test because of the good effect, low cost and high security.Engineering test for the landscape of reclaimed water takes ozone combined with ecological technique to maintain the water system and study the ultrafiltration treatment effect for high algae water. Ozone lateral circulation period is 5~7 days, and the dosage is 5 mg/L. After test because of water self-purification the TN decrease from 30 mg/L to 2~3 mg/L, TP decrease from 2 mg/L to 0.05 mg/L, the transparence of the water is above 0.4m, and the density of algae is below 108/L. The ecosystem is steady and with no water bloom appearance. When we supplement reclaimed water, water bloom appears because of the external pollution sources. The chroma of landscape is mainly due to the algae. The ions in water don't accumulate, and heavy metal content is lower than the detection limit. The main organic materials in reclaimed water are hydrocarbon and hydroxybenzene, and in lake water also include heterocyclic compounds and aromatic compounds. After ozone technique treatment the organic matters have more species but less quantity. Ozone can transform macromolecule to small molecular. After ultrafiltration technique the organic matters have less species but it has poor effect for lipid.The DO in Landscape Lake is above 8mg/L in 24h. The water ecosystem is steady, the change of pH is little, and without water bloom appearance. The self-purification of the landscape lake without ozone technique is weak. In reclaimed water TP is 0.31 mg/L, while algae content is slightly high. The ozone lateral system can enhance the ecosystem and self-purification of water. The dominate species in lake are green algae, and the dominance is not obvious in summer. As the seasons change, the algae in lake are diatom, chlorella, microcystis, and chlorococcumsp. During the operation, the electricity charge is 1.075$/h, and the maintenance cost is 0.18$/m3.h. We use pump to improve hydraulic condition, and the circle flux is 80m3/h, with five circle points. We also pot plants in lake, such as water lily, candock, bulrush, calamus, fleur-de-lis etc. and red carp in the lake rise from 5cm to 15cm at one year.