Class one ,NO.13
Dongmei li

Keywords ：sludge disposal waste water； filter backwashing waste water； iron and manganese remova1 ；giardia, cryptospohdium

Abstract：This paper discussed the reuse of a Waterworks waste water in Guangzhou ，analyzed the waste water quality problems in different conditions of direct reuse and reuse after being treated, put forward treatment technology about different waste water quality and gave some advices about the design and operation of reuse system

Forwords: At present , the evenironment problem is serious ,and the water population is the most outstanding and pressing problem. To many cities in our country , there are not enough water resource. So people consider of the water reuse and recycle, and use it for agricultural irrigation ,industrial, domestic and municipal supplies.
Guangzhou is a big city , the water volume of demand in Guangzhou is a large quality. There are five waste water treatment factories LieDe,DaTansha,LiJiao ,XILang and KaiFaQu waste water treatment factory. But it is far from enough. The most important is to use water reasonable and save water in all kinds of ways.

TEXT:The Waterworks waste water mainly come from settling tank or the sludge disposal of the clarifier filter backwashing waste water which can occupy 3%~7% of the water day output in whole Waterworks. The reuse of this part of water ,not only can save water ,enhance the operation of Waterworks, but also can reduce the waste displacement ,especially to the Waterworks whose condition of waste water displacement isn’t good, Recently, the large-size Waterworks out or in abroad have considered the reuse of waste water. But because of the problem of water quality, quite a number of Waterworks haven’t or unfrequently reuse waste water. Not only assemble all of the inpumties in raw water, but also include all kinds of medicament added in the product peocess. This matters come back to the manufacture system and some organism factors .such as, grardia and cruptospohdium. So in some degree, it will be dangerous .

1,The pattern of waste water

a)Direct reuse

Direct reuse is a popular parttern in the country at present. It includes the direct reuse of filter backwashing waste water and the reuse the waste water of manufacture. The former should install reuse tank to collect the filter back washing waste water ,and reuse before the raw water flocculation, The sludge in the bottom come to the sludge treatment system or discharge into river course,The fashion is fairly cheap. We can combine the sludge treatment system and implement 　together. But we need to strength the measure of water quality monitoring,Once the quality of reuse water can’t satisfy the reuse standard, should cut down the load of recycle or not to reuse .

b)Reuse after being treated

The reuse after being treated is to deal with the waste water, and reuse when the water quality can meet the rule chemical target and biological target. There are intimate realation between the treatment pattern and the quality of waste water. If the treatment expenses exceed the cost of raw water and there are enought raw water. That isn’t necessary to reuse waste water.

Well, Fig1~3 show the three different Waterworks reuse flow chart.

2. The problems of the reuse of waste water and the theatment

When we reuse the waste water , we should pay attention to the conversation index of iron ,manganese and microorgamism. Such as ,grardia and cryptospohdium. The excess iron and manganese is a chromic posion to people . Waterworks concern the removeal of iron and manganese rather than the requestment on toxicology .

The taste of the iron and manganese are terrible, so it can’t be drank until it be removed. At present , the standard of iron and manganese for drinking water in our country is 0.3mg/L and 0.1mg/L .Usually ground water has high concenrrations of iron and manganese. But to some surface water, the consistenoy of iron and manganest of water quality also go beyond the standard. If we reuse the waste water without treatment , the assemble function will affect the water quality.

There are many ways to remove the iron in the water. In the engineering, mainly use nature oxidizing agent, chlorination and touch oxidizing agent. The different peocesses suit for different situation. The mainly pattern to eliminate managese are　 permangamute oxidize, exposed the chlorine to the filtering and Photochemistry oxidizes

In generally, the iron and manganese will exceed quota at the same time. So we usually adopt corporation .

Fig4 show the diagram in common use.

3. The design and operation of the water reuse system

when designing the reuse tank ,we think of the real regular pattern of waste water to do our best to well-distributed reuse and reduce the lash load. But it will enlarge the volume of reuse tank , and it causes the difficultly to arrange factory building. So it need consider completely. For example , to design a Waterworks ,due to the sludge dehydration system include the sludge disposal waste water and filter backwashing waste water. So the only thing we should do is to concern the collection and reuse of chilly water.

Anglyze the process work flow in the sludge disposal waste water concentration there are 24 continuous work ,the volume is 165m³/h; in the filter backwashing waste water, there are 9.4 h work a day the volume is 391m³/h. So the summit volume is 391+165=556 m³/h. the other time is 165 m³/h.(14.5h).Thinking over the well-distributed, the average volume is2242 m³.Dueing to the space restriction, the factory couldn’t satify such a capacity, we can install a reuse tank beside the concentration .The reuse volume equal the discharge of the concentration.

The water treatment pattern, according to the requestment of waste water quality, we should consider the economic and reliability treatment process and make experiment to testify it .

Before operate the system , we must make reuse water standard ,and according to water quality automtic meter of Waterworks . So we can control the reuse water system with the database.

Conclusion:

1. Weather to reuse waste water,depands on the quality of raw water and producet waste water and some the other factors.

When the raw water can meet the requestment and cost lowly ,and the waste water should be treated before reuse ,even cost expensive,we have better neglect reuse. On contrary ,we can think of reuse waste water.

2.Thinking over weather to treat and reuse the waste water ,the key is the effect of treatment and the economic.Expecialy the latter one ,it decides the process.

3. It is better to combine the choice and desigion of reuse system,which are ozone and sludge treatment .