Waste to Energy

The concept of treating wastewater streams to avoid harmful impact to the environment has progressed to exploring reuse and energy generation from this waste streams. This focus had led to many studies to use anaerobic treatment processes, which has much lesser energy requirement and the end product also is an energy source. Yes, anaerobic biological processes is one, in which microorganisms break down biodegradable material in the absence of oxygen to generate methane. The resultant gas, a combination of Methane and Carbon dioxide is commonly known as Bio gas, which is combustible and can be used to generate electricity and heat, or can be processed into renewable natural gas and transportation fuels. 

Anaerobic digestion in wastewater treatment 
Anaerobic digestion already occurs in nature, whenever organic wastes are left under anaerobic conditions. But the process can be optimized, controlled, and contained using an anaerobic reactor. By analyzing the wastewater/sludge parameters, ideal reactors can be designed – be it traditional anaerobic digesters, sludge digesters, Continuously Stirred Tank Reactors (CSTR), or Upflow Anaerobic Sludge Blanket reactors (UASB). These reactors are designed to provide ideal conditions for anaerobic bacteria to thrive and maximise biogas production. Biogas contains roughly 50-70 percent methane, 30-40 percent carbon dioxide, and trace amounts of other gases. The liquid and solid digested material, called digestate, is frequently used for soil amendment. 

Anaerobic digestion to treat wastewater, septage, or sludge from wastewater treatment plants has gained worldwide attention because it offers significant environmental and economic benefits. In addition to treating wastewater in order to protect our water bodies, this energy recovery helps to build economic resilience in the face of an uncertain future for energy production and waste disposal. 

In addition to energy recovery, anaerobic reactors can lower costs associated with waste water treatment. With little to no processing, biogas can be burned on-site to heat boilers or operate biogas stoves. Biogas can be used for Combined Heat and Power (CHP) operations, or biogas can simply be turned into electricity using a combustion engine, fuel cell, or gas turbine, with the resulting electricity being used on-site or sold onto the electric grid. 

The left over material after digestion is a nutrient-rich solid (after dewatering) or liquid material - it contains all the recycled nutrients that were present in the original organic material but in a form more readily available for plants and soil enhancement.