活性污泥运行过程中经常会出现泡沫的问题，特别是在遇到负荷冲击或者运行条件变化的时候，泡沫严重得时候会造成系统运行的失败。泡沫包括生物泡沫或非生物泡沫。
要解决泡沫的问题，首先要了解泡沫的特点，然后追根溯源找到出现泡沫的原因并最终找到合理的措施加以控制。
1.什么是泡沫
Foam is a mass of small bubbles of gas formed on the surface of a liquid, such as the froth produced by agitating a solution of soap or detergent in water. In the case of activated sludge, it can be several factors that cause foaming. Operational or non-operational problems can lead to all types of foaming.
目前，普遍认为生物泡沫形成的主要原因是：在各种因素影响下，造成丝状菌和放线菌等微生物的异样生长，丝状菌的比生长速率高于了菌胶团细菌，又由于丝状菌的比表面积较大，因此，丝状菌在取得污水中BOD5物质和氧化BOD5物质所需要的氧气方面都比菌胶团细菌有利得多，结果曝气池中丝状菌成为优势菌种而大量增值，导致生物泡沫的产生。再加上这些微生物大都呈丝状或枝状,易形成网,能捕扫微粒和气泡等,并浮到水面。被丝网包围的气泡,增加了其表面的张力,使气泡不易破碎,泡沫更加稳定。另外，曝气气泡产生的气浮作用是泡沫形成的主要动力因素。研究发现，与生物泡沫有关的菌属主要有Nocardioform actinomycetes(放线菌)和Microthrix parvicella(丝状菌)等，前者多出现于夏季，后者多出现于冬季。
2.泡沫的分类
2.1 曝气池泡沫Normal Activated Sludge Foam
Normal activated sludge will have a light tan color and cover anywhere from 10 to 25% of the surface of the tank. The bubbles on the surface will disperse quickly. normally activated sludge foam 在常规的活性污泥处理厂中比较常见。不需要特别的处理。
2.2 Stiff White Foam
Stiff white, billowing foam, indicating a young sludge (low MCRT) is usually found in a new plant or an overloaded plant.这种泡沫的成因是短的活性污泥停留时间，在新的水厂比较容易出现。
白色泡沫产生的原因很多，但主要常见于负荷过高、曝气过度、洗涤剂流入等。而在区别是何种原因导致的白色泡沫时，泡沫的黏度能给我们很多的参考。通常情况下，粘稠不易破碎的泡沫，常见于活性污泥负荷过高，而且此时的泡沫色泽鲜白，堆积性较好，而粘稠易破碎的泡沫常见于活性污泥的过度曝气，而且此时的泡沫色泽为陈旧的白色，堆积性差，只会发生局部堆积，洗涤剂的流入也会发生白色的泡沫，因为洗涤剂的存在，增加了水体的表面张力，最终导致泡沫的形成。
2.2.1 成因
这种泡沫在新的污水处理厂或者Overloaded的污水处理厂较为常见。这种泡沫意味着污水处理系统中MLSS过低，F&M过高。课程的原因如下
a.没有回流污泥
b.启动初期MLSS较低
c.目前运行条件下，有机物负荷较高，MLSS较低，F/M值与白色泡沫的关系。如果F/M值过高（大于0.5），同时对应产生大量白色粘稠泡沫的话，我们就可以认为活性污泥确实是处于高负荷运转状态了。
d. 运行条件异常，如pH低于6.5或高于9.0，溶解氧浓度不够，营养物质匮乏或者季节性温度变化。
e.各种原因导致的系统污泥六十。比如突然的水力负荷增大Excessive or shock hydraulic loads，生物系统运行问题biological upset, high sludge blanket in secondary clarifier resulting in solids washout, mechanical deficiencies in the secondary clarifier (leaking seals, open de-watering valves), Improper distribution of flows or solids loadings to multiple clarifiers.
2.2.2 控制措施
检查回流污泥，确保回流污泥系统运行正常。
暂停系统排泥提高系统中的污泥浓度。
调整DO，使其在1到3之间。在保证活性污泥供氧的情况下，尽量降低曝气量，不但能减少泡沫产生，同时也能减少能源消耗，降低运行成本。
Consider hauling in seed activated sludge if warranted
–Actively enforce sewer use ordinances to avoid process upset and deterioration of the secondary system. Check out the distribution of return sludge, and influent into the basin for proper flow split.
–If flow meters are not provided, visually check the return sludge flow and compare to the following:
•The sludge blanket levels in each clarifier
•The return sludge TSS concentration from each clarifier
•The MLSS concentration in each aeration tank.
2.3 Heavy Brown Foam
A heavy dark scummy foam is typical in plants that practice sludge re-aeration. the scummy dark foam indicates an older sludge and can result is other problems downstream of the aeration tank. There could also be a presence of Nocardia in the sludge.
这一类的泡沫可能是由于污水处理厂污泥老化造成的。
2.3.1 成因
这种泡沫一般出现在低负荷运行的污水处理系统。比如以生物硝化为目的的污水处理厂在运行过程中在硝化池会出现一些黑褐色的泡沫。
Plants with filamentous organisms Nocardia will have a strong greasy dark tan foam that will carry over onto the clarifier surface. Scum containing filamentous organisms should be wasted from the system rather than returned to the aeration tank.
A heavy dark brown greasy foam is usually normal while operating in the re-aeration mode of operation.
–Aeration tank is being operated at a low FM, possible because nitrification is required by the regulatory agency.
–Build-up of a high MLSS concentration as a result of insufficient sludge wasting. This condition could unintentionally occur between the winter and summer seasons when wastewater temperatures change, which affects microorganism growth and activity.
–Operating in sludge re-aeration mode.
–Improper wasting control program
活性污泥处于缺氧状态，缺氧的状态可使活性污泥出现局部的厌氧反应，这样，原本处于好氧状态的活性污泥就会在这个转变的过程中出现死亡，同样也就会附着在曝气时的气泡上了。所以如果我们看到产生的泡沫呈灰黑色的话，除了确认进水是否含有黑色染料废水外，主要就是要确认生化池是否在局部有曝气不足产生的厌氧情况发生。
2.3.2 控制
–If nitrification is not required, gradually increase the F/M and decrease the MCRT.
–If the scum is not returned to the aeration tanks, include the volatile solids removed in the scum in the waste sludge calculations. During normal operation, the amount of volatile solids removed with the scum is to small to matter. However, during periods of high foam, 10 to 15% of the solids may be removed with the scum.
–If filaments appear, try to identify the cause. There are several books on the market that will help you identify the type of filament and how to control it. A microscope is a must in the identification of filaments.
2.4 M Parvicella Foam
Stable dark brown greasy foam that can get thick enough to have a crust- plant with Microthrix problems due to grease problems in the lift stations, or collection systems.
泡沫产生时数量不多，靠近曝气团四周液面少量产生，沿辐射方向逐渐消散，到四周角落时开始积聚，泡沫颜色呈棕黄色，泡沫色与当时活性污泥颜色相同。整个泡沫形成到积聚的过程中，泡沫呈易碎状态，所以此类泡沫在短时间内不会发生严重的积聚而导致大量浮渣产生。
Thick scummy dark brown foam indicates an old sludge (high MCRT) and can result in additional problems in the clarifier by building up behind the influent baffles and creating a scum disposal problem as shown below:
活性污泥处于老化状态，部分活性污泥因为老化而解体，悬浮在活性污泥混合液中，在曝气状态下均匀附着在泡沫中，导致泡沫破裂的时间延长，这为泡沫积聚创造了条件。
工艺判断：
此类泡沫产生是污泥处于或即将进入活性污泥老化状态的一种表现。
（1）活性污泥的沉降比方面。通过沉降比值是否偏小，沉降的活性污泥是否色泽暗黄，沉降速度是否过快等方面的确认，结合液面产生的棕黄色泡沫即可较为准确的判断活性污泥是否出现了老化现象。
（2）SVI值方面。当SVI值低于40的时候，活性污泥通常发生了老化，结合液面产生的棕黄色泡沫即可较为准确地判断活性污泥是否出现了老化现象。
（3）显微镜观察结果。如果观察到的菌胶团比较致密，且后生动物大量较多，结合液面的棕黄色泡沫，可以判断活性污泥是否处于老化阶段。
2.5 Other Foaming
Foam can be caused by an industrial user who is overloading the facility.
2.6 Foaming from Septicity
Foam can be caused from septic condition throughout the municipality.
3. 膨胀有关的微生物
Nocardia 是经常被提到的导致活性污泥膨胀或者引起泡沫的微生物之一。Nocardia是一种丝状菌，过量生长还会引起活性污泥丝状菌膨胀。
其控制措施包括
1.控制污泥停流时间。
2.投加化学药剂控制泡沫之前一定要搞清楚系统的问题然后对症下药。可以添加的化学药剂包括
a.聚合物可以直接加入回流污泥或者曝气池内，
b.投加次氯酸钠或者氯气。这种措施可以杀死丝状菌，但不一定会对泡沫产生作用。
c.消泡剂
d. Skimming the foam Skimming the foam to a place to get rid of it would help
e. 用水冲，在活性污泥曝气池上安装曝气头可以有效控制泡沫，至少可以利用其压力将形成的泡沫打碎
f. Submerged and surface overflow – Submerged aeration basin gates can contain foam from exiting to the secondary clarifier. This makes getting rid of foam much more difficult. Surface overflows out of the aeration basin can help get foam to the secondary clarifier and then skimmed off the surface.
g. Impacts on Digestion – Foam generated from the secondary process, especially Norcardia foaming can present many issues in a digestion system. Foam can overflow a digester on the ground, cause volume issues, gas piping issues, and digester operations. to correct digester foaming, the secondary process must be corrected of Nocardia in the system.
4.活性污泥系统中泡沫的检查
由于活性污泥系统中的泡沫来源多种多样且表现各异，因此在遇到泡沫的问题时，需要对其进行仔细分析，找准泡沫出现的原因，从而有效的对其进行控制。
5.非生物泡沫
非生物泡沫行程中最常见的是表面活性剂气泡。污水中的表面活性剂和淀粉、蛋白质、油脂等表面活性物质在分子结构上都表现为含有极性－非极性基团即所谓双亲分子，在曝气的条件下，非极性基团一端伸入气泡内，而极性基团选择地被亲水物质所吸附，这样亲水性物质的表面被转化成疏水性物质而粘附在气泡水膜上，随气泡一起上浮至水面。各种悬浮物质若混入表面活性剂等产生的泡中，这些物质单独存在并不能发泡,但是可使泡沫稳定。如造纸工艺也中的微细纸浆，食品工业中的纤维质等。另外，如氯化钠、硫酸钠、硫酸铝等盐类的水溶液,单独存在几乎不产生泡沫,但也有助于泡沫的稳定，使泡沫难以消失。