BOEEP Tells You Sludge Treatment Methods

Generally speaking, the cost of sewage treatment and sludge treatment is basically the same in urban or industrial wastewater treatment.

• The purpose of sludge treatment

1. Reducing water content and volume to facilitate sludge transportation, storage and various treatment and disposal process.

2. Make sludge sanitary and stable. Sludge often contains a large amount of organic matter, may also contain a variety of pathogens, and sometimes contains other toxic and harmful substances. It is necessary to eliminate these factors which can emit odor, cause diseases and pollute the environment, so as to make sludge sanitary, stable and harmless.

3. Through treatment, the composition and properties of sludge can be improved, which is conducive to its application, and the purpose of energy and resources recovery can be achieved.

   
   

• Sludge treatment methods

  Commonly used sludge treatment methods are concentration, digestion, dehydration, drying, incineration, solidification and final disposal. Sludge thickening, sludge digestion and sludge dehydration are the most widely used treatment methods.

  
  

  Common solutions as below,

• Raw sludge → Concentration → Digestion → Natural drying → Final disposal

• Raw sludge → Concentration → Natural drying → Compost → Final disposal

• Raw sludge → Concentration → Mechanical dehydration → Drying-Incinerating → Final disposal

• Raw sludge → Concentration → Mechanical dehydration → Final disposal

• Raw sludge → Concentration → Digestion → Mechanical dehydration → Final disposal

• Raw sludge → Concentration → Digestion → Mechanical dehydration → Drying-Incinerating → Final disposal

• Sludge incineration

  After incineration, the moisture content of sludge can be reduced to 0%, which simplifies transportation and final disposal. Sludge should be effectively dehydrated before incineration.

  The sludge incineration process is suitable for the following situations,

1. When the sludge does not meet the hygienic requirements, the toxic substance content is high, so it can not be used as agricultural utilization.

2. Large and medium cities with high hygienic demand and tight land use.

3. The sludge itself has high calorific value and can self ignit and generate electricity by burning heat.

4. Mix incineration with municipal refuse and generate electricity by burning heat.

• Sludge digestion

  Sludge produced in the process of wastewater treatment, which is mainly composed of organic substances, is called fresh sludge or raw sludge.

  The sludge that needs digestion is gelatinous, and it is not easy to dehydrate. The contents of nitrogen, phosphorus and potassium in sludge are organic and are not easily absorbed by plants. The organic matter in the sludge is very unstable, and it tends to decay and stink. Some of the sludge contains pathogenic bacteria and parasitic eggs, which are easy to transmit diseases.

  Sludge digestion is to stabilize organic substances in sludge, remove odor, kill most pathogenic bacteria and ascarid eggs, reduce sludge volume and recycle energy such as biogas produced in digestion process by means of microbial metabolism.

  Sludge digestion is a process of stabilizing organic matter in sludge through microbial metabolism under manual control. Generally, there are two processes, aerobic digestion and anaerobic digestion, which utilize the metabolism of aerobic microorganisms and anaerobic microorganisms to stabilize sludge.

  
  

• Sludge recycling

1. An amendment used as fertilizer or soil.

2. The amount of heavy metals or toxic and harmful substances in sludge is too high to be used as fertilizer. It can be used for building products. For example, bricks made from sludge.

3. Anaerobic digestion of sludge produces biogas.

4. Activated carbon from sludge, fuel from sludge, sludge as adsorbent, etc.

   
   

• Disposal of sludge

  Sludge disposal should be considered when sludge can not be reused.

1. Landfill

2. Incinerating

3. Ocean dumping

In the previous article, BOEEP brought you a deep understanding of sludge. This time, we explained the sludge treatment methods. In the next chapter, we will explain sludge concentration in detail.