一、 方案依据及目标：

1、依据：

1.1 平均日处理污水量140吨，设计能力为日处理量为200吨。

1.2 要求连续处理、操作方便。

1.3 设备使用年限≥15年

2、目标：

要求采用本方案处理后的污水中

总铬含量＜1.5mg/L

六价铬含量＜0.5mg/L

PH值为6–9

磷酸盐（以P计）＜0.5mg/L

化学需氧量＜150mg/L

铜含量＜0.5mg/L

锌含量＜5mg/L

二、 方案设计：

2.1   总体设想：

该方案处理方法采用的是氧化还原法处理六价铬，使其转化为三价铬，然后再用化学沉淀法除去重金属离子，该工艺运行稳定、效率高、操作简便、运行成本低。东风汽车公司许多表面处理车间采用该方法应用多年，实践证明使用效果非常好。

该项目获得中国汽车工业科技进步奖三等奖。
2.2    基本原理：

基本原理：在反应池中控制废水PH＜6时加入还原剂，使六价铬转化为三价铬，然后调节PH值到8–8.5，将废水中的三价铬、铜离子、锌离子、锰离子、铁离子等转化为氢氧化物形成沉淀，再加入絮凝剂是小颗粒沉淀絮凝成大块沉淀物，同时在这个过程中将其他一些禁止排放的物质沉淀。然后在沉淀池中进行泥水分离，清水从沉淀池上面排出，污泥经管道到污泥浓缩池，最后经压滤机将污泥压滤成块，送转厂烧砖，彻底消除污泥的二次污染。

2.3 储水池设计：

储水池容积的大小由车间水的流量，反应池处理时间，同时要兼顾系统的意外停工时间等因素决定。根据项目委托书中的要求，车间平均日废水排量为120吨，将储水池容量设计为80吨，加上两个反应池容量就能达到120吨的储水量，也就是说在正常生产情况下污水处理系统可以有一天的维修时间。储水池的设计要有利于废水的充分混合，考虑到大块悬浮物的隔离，防止堵塞管道，因此我们设计了隔油板。除了储存车间来水，储水池同时也起调整作用，即使得废水浓度相对均衡，以保证进入反应池的废水浓度相对有一个小的波动范围。在储水池的布置上充分利用厂区的高度差，采用自流方式以节约能源，同时考虑厂区美化，将储水池布置于地面下，池上覆盖草坪。                 

2.4  反应池的设计：

反应池由两个池组成，每个反应池的有效容积均为15吨，交替使用。这样使得其中一个池在进行氧化还原处理时，另外一个池可以接受从储水池流过来的废水，从而保证废水处理的连续性。该反应池设计在地面以下，既能保证水能自然流到池中，减少电能消耗和水泵维修，同时也使加料操作方便安全。
为了使化学反应快速均匀，缩短处理时间，在反应池中安装了空气搅拌；加料和调节PH值采用人工控制。反应完毕通过污水泵将处理合格的污水送到沉淀池进行分离。

2.5 沉淀池的设计：

沉淀池的设计在整个环节中至关重要，因为反应生成的沉淀若不能及时分离，既影响达标排放，又制约法治水处理效率。根据日处理量，我们设计的沉淀池容积为160m3，为了提高沉淀效率，在沉淀池内安装了斜管沉降器， 以确保出水质量， 在沉淀池底部的泥浆则通过泥浆泵或自流形式将泥浆送到污泥浓缩池，同时为便于察看沉淀效果，在沉淀池的上面设计了走道。

沉淀池的底部设计为漏斗状，便于泥浆集中于斗底，有利于排出。沉淀池的溢流槽采用三角堰出水，以消除流水造成的纹流，防止沉淀在斜管上的泥被带出，造成水质不清。沉淀池的深度则根据沉淀的四个区域来决定，即清水区、斜管沉降区、过渡区、污泥区。一般情况下，清水区的高度要在合理的范围内，可防止排水口水的流动带起斜管沉淀上的污泥。斜管沉降区则依据选择的斜管长度，斜管沉降器选用非常重要，斜管沉降器是根据浅池沉淀原理；过渡区是进水分布区，该区设计时要尽量使进水分布均匀，防止水流短路，可在进水口加装导流板，尽量延长水运动路径，污泥区应根据污泥量的排泥间隙，同时在设计时，尽量让污泥朝排泥口移动，以便排泥。

2.6 污泥浓缩池的设计：

污泥浓缩有效溶积为16m3。

2.7 污泥压滤：

污泥压滤采用板筐式压滤机，它属于标准设备，购买后安装即可使用。压滤机的使用能使污泥的体积头少到原来的5%，而且经压滤空气吹干，储存和运输都很方便，原污水处理系统无法正常运行，很关键的一条就是没有采用污泥干化技术，造成大量泥浆无法处理，压干的泥块存放到一定数量后送砖厂烧砖，从而彻底消除二次污染。

2.8 管道系统：

车间来水通过原水的排水沟直接流到储水池，储水池的水经过地下管道￠300陶管（或水泥管），通过两个阴井到反应池，第一个阴井在管道转向时防止堵塞，第二个阴井到两个反应池有两路管道，分别引向两个反应池，采用￠200钢管并加装阀门控制，以便轮流将废水排入反应池，从反应池到沉淀池通过￠80-100管道连接，并用污水泵提升，污水泵流量为25m3/小时，扬程20m。沉淀池到污泥浓缩池的污泥管道采用￠100-120管道连接，并通过污泥泵抽吸，污泥泵采用15m3/小时，扬程15m。从污泥浓缩到压滤机所用的泵及管道规格和板筐式压滤机相配套。

压缩空气来源于小功率的空压机，其规格为1–1.2m3/min，管道采用￠30的钢管，使用压缩空气的点有压滤机、反应池、及污泥浓缩池。

2.9 控制电路：

电源控制柜置于站房内，总功率为50kw，给三台水泵电机，一台油压电机，一台空压机电机及照明供电。

一、  Basis and Target of the Plan

Basis:

The average daily treatment capacity shall be 140 Mt and the design capacity 200 Mt per day.
It is required to treat the waste water constantly, and the operation must be convenient.

Equipment life time ≥ 15 years

Target:

It is required that in the treated waste water

Overall chrome content < 1.5mg/L

Hexavalent chrome content < 0.5mg/L

PH value: 6-9

Phosphate (P) < 0.5mg/L

Chemical oxygen demand < 150 mg/L

Copper content < 0.5mg/L

Zinc content < 5mg/L
二、 Plan Design

General:

We adopted the method of oxidation reduction to treat the hexavalent chrome, transform it to trivalent chrome, and remove the heavy metal ions by means of chemical precipitation method. This process features in its stable performance, high efficiency, simple operation and low operative costs. In the DongFeng Auto Corporation there are quite a few surface treatment workshops where this method has been put into production for years and its practical effect has been proven to be good.
This project has also been awarded as a Class-3 Advanced Industrial Technology of China Auto.
Principle: Add reducer when the waste water in the reaction tank is controlled as PH < 6, transform the hexavalent chrome into trivalent chrome。 Regulate the PH value to 8-8.5; transform the trivalent chrome, copper, zinc, manganese and iron ions into hydroxid to let them settle. After that add flocculating agent to make the small grain flocculation become large grain flocculation,Meanwhile ,settle other substances which are forbidden to discharge.Separate the mud and water in the settling basin, the mud is transferred to the mud condensing pool through the pipes, and then pressed into blocks by the pressing and filtering machine. Finally the secondary pollution of the mud is removed after burning it into brick.

Design of Water-storing Tank
    The size of tank is determined according to the water runoff in the workshops, the treatment time in the reaction tank, and any possible interruption and disturbance. As required by the Project Entrusting Documents, the average daily waste water output is 120 Mt. In our design the tank capacity is 80Mt, in addition to the two reaction tanks; the overall water storage capacity reaches 120Mt. That means under normal production conditions the waste water system may have a One-day maintenance time.The tank design must be suitable for the fully mixing of waste water. Taking account of the separation of large suspended matter blocking the pipes, we have designed an oil-separation plate. Except the function of storing the water from the workshops, the tank may also play a regulating role to enable the waste water thickness keep a relatively balanced level that will avoid large thickness difference of the waste water in the reaction tank.  For the location of tank, we have taken advantage of the altitude difference in the plant area to form automatic flow and therefore save power. Also for the purpose of the landscaping, we have designed the tank below the ground and covered by lawn. The tank structure is as follows:

Design of Reaction Tank
    The reaction tank is formed of two tanks, each has a 15 Mt storing capacity and they are utilized alternatively. When one is performing oxidation reduction treatment, the other may receive the waste water from the water-storing tank so as to keep a constant waste water treatment. The tank is designed below the ground and enables the water automatically flows to the tank, saving either power consumption or pump maintenance costs, and material feeding becomes simpler also.
In order to enable quick and balanced chemical reaction and shorten the treatment time, there is air mixer installed in the tank. Material feeding and PH regulating are controlled manually.Once the reaction is finished, the waste water pump transfers the treated and qualified waster water to the settling resin to separate it.  

Design of Settling Besin
    This is a key point, because if the settling substances resulted from the reaction is not separated immediately, then the discharge will not meet the standard and the treatment efficiency will be restricted also. Based on the daily treatment volume, we have designed a 160m3 settling resin. In order to increase the settling efficiency we have installed an oblique pipe settling device in the tank to ensure the outlet water quality. In the tank bottom the mud is transferred to the mud condensing pool by the mud pump or automatic flow. Meanwhile, for the purpose of watching the effect we have designed walkway above the settling resin.

The resin bottom is a funnel shape which allows the mud comes to bottom and therefore is convenient to be transferred out. The overflow port of the resin is a triangle weir to avoid watermark flow that means the mud on the oblique pipe will not be taken out and the water will remain clean. The depth of the resin is determined according to the four areas of settling: Clean water area, Oblique pipe settling area, Transition area and Mud area. Most of time, the depth of the clean water area must be at a reasonable level, that will avoid the water flow to take away the mud on the oblique pipe。The settling area’s depth is determined by the length of the pipe; as a result, the selection of the settling device is important. This device is based on a shallow resin settling principle. The transition area is for inlet water; here the water must be balanced to avoid water flow short-current. It is recommended to install a diversion plate to extend the water movement. For the mud area, we should consider the time interval of mud removal。 Try to lead the mud to move to the mud outlet. The settling resin structure is as follows: Design of Mud Condensing Tank

Available capacity: 16m3

Mud Press and Filtration

We use basket filter press; it is standard equipment which may be utilized immediately after installation. The filter press may decrease the mud cubage to 5%. And once it is dried the storage and transportation will be much more convenient. The reason why the original waste water treatment system could not function normally is that this technology is missed and large amount of mud could not be treated on time. In our design, the dried mud block will be burned to brick and comb-out the secondary pollution.
Pipe System。

The water from the workshop flows to the storing tank from the outlet channel directly，The water in the tank then flows to the reaction tank through ￠300 underground pottery pipes (or concrete pipes)。  Through two water-transit wells, one is located in the pipe corner to avoid blocking and the other has two pipes connecting the two reaction tanks.They are ￠200 steel pipes and controlled by valves, which enable alternatively transfer the waste water to the reaction tank. The pipes connecting the reaction tank and the settling resin are ￠80-100 pipes.Waste water is pumped with a runoff of 25m3/hr, and the pump lift is 20m.The mud pipe from the settling resin to the mud condensing tank is ￠100-120 and supported by a mud pump which is 15m3/hr. (Runoff) and15m (pump lift). The spec. of the pump and pipes from the mud condensing to the filter press must match the basket filter press.  

The compressed air is from a small power air compressor and its spec. is 1–1.2m3/min. The pipe is ￠30 steel. The filter press, reaction tank and the mud condensing tank all need the compressed air.
Controlling circuit。

The electrical cabinet is in the station, with a full power of 50kw, it provides power to the three pumps, one electric motor for oil pressure, one electric motor for air compressor and lighting.