Biogas Systems for Treatment Plants
Almost all wastewater treatment plants (except very small ones) need electrical power for operation. In fact, for wastewater treatment plants, energy is usually the highest individual cost item. Therefore, owning and operating a wastewater treatment plant requires considering how to obtain electricity for operation at the lowest possible cost.
Currently and for the foreseeable future, most of the world's energy is produced by fossil fuels. Due to the continuous depletion of those resources and the hunger of the developing nations for energy, prices for fossil fuels and coincidentally the prices for electricity generated from those energy sources are on the rice and will continue to increase.
Furthermore, some regions will have to deal with energy shortages and regular block-outs. In those areas, the operators have the choice of leaving the plant powerless and non-functioning for the time of the energy outage or to invest in expensive back-up solutions such as diesel generators that add to the cost. In consequence, the operation of wastewater treatment plants will become more expensive over time.
For owners and operators of treatment plants, finding new and less expensive energy sources will have a great impact on investment decisions, profitability and might even become a matter of survival. Several options are available to tackle this issue. All of them are related to the use of renewable energy.
At BIO-4 , we believe that the best option to approach the topic of energy supply lies within the plant itself. If the plant is able to reduce energy consumption from outside sources to a minimum, operations cost would drop and the plant would reduce its exposure to volatile energy prices.
As part of the treatment process, the plant “produces” surplus sludge as a by-product. While this sludge can be used in many different ways (see sludge treatment options), it can also be fermented. During the fermentation process, energy rich biogas is produced that can be burned to generate electricity and heat. Since biogas can generally be extracted from all organic substances, organic material (e.g. from agriculture) can be added to the sludge to increase the energy production in the wastewater treatment plant with a connected biogas system.
Application of Biogas Systems in Wastewater Treatment Plants
Operators/owners of wastewater treatment plants can benefit from a biogas system if the plant is large enough to produce an amount of biogas with which a continuous power generation is possible. Plants below 50.000 PE are usually not suited for biogas systems, plants between 50.000 and 75.000 PE are partly suited and plants above 75.000 PE are usually well suited for biogas systems. Smaller plants, however, could be equipped with biogas systems when there is biomass from other sources (e.g. agriculture) available in the vicinity at low cost for additional biogas generation.
If the size requirements are met, plants are particular beneficial when:
Electricity is very expensive and prices are not guaranteed
Energy supply is frequently interrupted due to shortages or for other reasons
The generated heat can be used for other purposes (e.g. warm water generation, heating, industrial processes, agriculture)
From our experience, we generally recommend biogas systems for plants larger 75.000 PE. In any case, prior to recommending a specific biogas system, we will develop a business case together with you to calculate the economics of such a system. The economics mainly depend on electricity cost, cost of operating the biogas system and the initial investment for the system.
It is essential that a wastewater treatment plant and a biogas systems work seamlessly together to achieve optimal results in saving electricity and cost. Therefore, we believe that the work should be carried out by someone who considers both system in unity from the start and integrates leading technology suitable for the specific application. At BIO-4, whenever we plan a biogas system for a new or existing plant, we closely cooperate with companies specializing in the design of biogas equipment such as reactors and generators. With that we ensure that you get a state-of-the-art biogas system that precisely fits to your plant and fulfills your expectations.

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