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What are the operational costs of aerobic vs. anaerobic treatment?
Updated: Sep 9
Overview
Aerobic and anaerobic treatment both use microorganisms to break down organic matter in wastewater, but their running costs can be quite different. Aerobic systems need a continuous supply of air, while anaerobic systems work without oxygen. This difference affects electricity use, sludge production, equipment and daily plant operation. The operational costs of aerobic vs anaerobic treatment also depend on wastewater strength, plant size and discharge requirements. This blog compares the main expenses in both processes, including aeration, chemicals, sludge handling and maintenance, to help ETP operators understand where their treatment budget is being spent.
Table of Contents
What Affects Wastewater Treatment Operating Costs?
There is no standard operating cost that applies to every ETP.
The main factors affecting wastewater treatment operating costs include wastewater flow, COD and BOD load, electricity price, chemical use, sludge production, labour, equipment maintenance and the quality required at discharge.
A plant treating low-strength wastewater may have a very different cost from one treating wastewater with a high organic load.
For this reason, an ETP operating cost comparison should use actual plant data rather than only the size of the treatment tank.
Aerobic Treatment: Where Does the Money Go?
Aerobic treatment uses microorganisms that need oxygen to break down biodegradable organic matter. Blowers or other aeration equipment supply this oxygen.
Electricity is often a major part of the aerobic wastewater treatment cost because aeration equipment may run for long periods.
Blower power consumption ETP data should therefore be checked when reviewing running costs. Blocked diffusers, air leaks, poor oxygen transfer or incorrect blower operation can increase electricity use.
Good aeration energy efficiency means supplying enough oxygen for treatment without wasting air or electricity.
Aerobic systems also produce biological sludge. This must be removed, dewatered and disposed of, making sludge disposal cost another expense to consider.
Anaerobic Treatment: What Are the Main Costs?
Anaerobic microorganisms break down organic matter without oxygen. This removes the need for continuous aeration inside the anaerobic reactor.
For suitable high-strength wastewater, this can reduce wastewater treatment energy consumption compared with an aerobic process.
The anaerobic wastewater treatment cost, however, does not disappear simply because blowers are not required for the main biological stage.
Pumps, mixing, heating in some systems, monitoring and maintenance can still consume energy and money. Anaerobic plants may also need careful process control because the microorganisms can be sensitive to sudden changes in pH, temperature and loading.
Treated water from an anaerobic process may require further treatment before discharge, which also needs to be included in the cost calculation.
Aeration and Electricity Costs
The biggest difference in the operational cost comparison between aerobic and anaerobic treatment is often aeration.
Aerobic microorganisms require oxygen, so blower power consumption ETP can account for a considerable part of plant electricity use.
Anaerobic treatment avoids this aeration requirement in its main reactor.
But wastewater treatment energy consumption should be calculated across the whole plant. Pumps, mixers, sludge equipment and any treatment after the biological stage all use electricity.
Looking only at the biological reactor can give an incomplete cost comparison.
Chemical and Sludge Costs
Both processes can require chemicals depending on the wastewater.
The chemical dosing cost wastewater plants face may include pH correction, nutrients, coagulation or other process chemicals.
Chemical requirements vary with wastewater composition, so the cost should be calculated from actual consumption.
Sludge also affects biological treatment operating expenses.
Aerobic treatment generally converts more organic matter into new biomass than anaerobic treatment, so it commonly produces more biological sludge. More sludge can mean higher thickening, dewatering, transport and sludge disposal cost.
How Much Does Aerobic Wastewater Treatment Cost to Operate?
When asking how much does aerobic wastewater treatment cost to operate, calculate the major costs separately.
Include electricity, chemicals, sludge handling, labour, maintenance and replacement of worn equipment.
Where biological activity needs support, BactaServe Aerobic is intended for aerobic wastewater treatment systems and contains selected microorganisms for the breakdown of biodegradable organic matter.
Bioculture use should be considered alongside correct aeration, pH, loading and other operating conditions.
Is Anaerobic Treatment More Economical Than Aerobic?
The answer to is anaerobic treatment more economical than aerobic depends mainly on the wastewater and treatment target.
Anaerobic treatment can be attractive for high-strength organic wastewater because it has no aeration requirement in the main reactor and usually produces less biological sludge.
But asking which is cheaper aerobic or anaerobic wastewater treatment requires looking beyond electricity.
Capital equipment, heating, process control, maintenance and any treatment needed after the anaerobic stage can change the calculation.
The lifecycle cost wastewater treatment plants face should include both initial investment and costs across years of operation.
Conclusion
The operational costs of aerobic vs anaerobic treatment cannot be judged from aeration costs alone.
Aerobic treatment usually has higher aeration requirements and can produce more biological sludge. Anaerobic treatment uses less aeration energy in the main reactor but may have other operating requirements and may need further treatment before discharge.
A useful ETP operating cost comparison should include energy, chemicals, sludge, labour and maintenance.
For aerobic plants where microbial support is needed, BactaServe Aerobic may form part of the biological treatment programme after plant conditions have been checked.
Which is cheaper aerobic or anaerobic wastewater treatment?
Which is cheaper aerobic or anaerobic wastewater treatment depends on wastewater strength, plant design and discharge requirements. Anaerobic treatment often has lower aeration needs, but other costs must also be considered.
What are the main biological treatment operating expenses?
Biological treatment operating expenses include electricity, chemicals, sludge handling, labour, monitoring and equipment maintenance.
How much does aerobic wastewater treatment cost to operate?
There is no single answer to how much does aerobic wastewater treatment cost to operate. Plant flow, organic load, electricity rates, aeration requirements and sludge production all affect the cost.
How can aeration costs be controlled?
Checking dissolved oxygen, diffuser condition, air distribution and blower operation can improve aeration energy efficiency and help identify unnecessary electricity use.
Why should lifecycle costs be considered?
Lifecycle cost wastewater treatment calculations include more than the initial equipment price. They consider energy, chemicals, maintenance, sludge handling and other expenses over the working life of the plant.
