Biological Wastewater Treatment Systems -Natural Endogenous Respiration Vessel (NERV)Waterman Engineers Australia
Biological Wastewater Treatment Systems Overview
Due to rising population needs for clean and safe water supplies, biological wastewater treatment systems (BWTSs) have found widespread use not only in developed countries such as the Netherlands, but also in countries such as China. BWTSs can effectively remove COD/BOD, N, and P from wastewater, and they have minimal operational costs, with China and the Netherlands charging around 8 and 40 US$/ca year, respectively.
As a result, BWTSs have surpassed all other water pollution control devices. Despite decades of research on BWTSs, it is still too early to conclude that present systems are adequate enough in terms of process design and sustainability. Between our understanding of microbiological processes and the realities of engineering, there are still major knowledge gaps.
The NERV system provides variety and quantity control of isolated bacteria inside the reactor. Fresh bacteria are produced and grown outside the reactor, and continuous dosage guarantees that a steady availability of new bacteria is available at all times, even when nutrient levels are low or toxicity is high. This guarantees that microorganisms are not erased out, and that bio-remediation can resume quickly.
NERV is much more compacted than previous techniques, and when nutrient levels are low, the bacteria adopt an endogenous respiration condition, in which they consume their own biomass. When compared to typical biological systems, this leads in far less sludge creation. This technology has a far smaller carbon footprint than previous systems, as well as the idea of growing bacteria from outside the unit eliminates the need for the system to rely on self-generating bacteria, allowing it to withstand harmful impulses and severe nutrient changes.
Biological Wastewater Treatment Systems Principle
Endogenous processes encompass a variety of biological and ecological mechanisms and processes, such as endogenous respiration/cell maintenance, cell decay, death-regeneration/cryptic growth, higher microorganism predation on bacteria, and cell lysis due to viral infection or adverse environmental conditions (e.g., pH, temperature, and toxic substances). Almost every aspect of BWTSs is influenced by these mechanisms. The microbial community of BWTSs, and hence the capacity, efficiency, and robustness of treatment systems, are affected by endogenous processes.
Predation may cause overgrazing of nitrifying bacteria, causing the nitrification process to deteriorate. Increased effluent P-concentration has been linked to either excessive decay of intracellular storage polymers, 9 or excessive decay of both phosphate accumulating organisms (PAOs) and intracellular storage polymers in enhanced biological phosphorus removal (EBPR) procedures.
A considerable portion of electron acceptor usage is due to endogenous mechanisms. Endogenous respiration was discovered to utilize more than half of the total oxygen supply for COD elimination. Furthermore, endogenous processes have a considerable impact on waste sludge generation (biomass). In most BWTS plants, biomass processing and disposal contribute for 50–60 percent of the capital and operating expenditures.
Bacteria are the most active and prevalent microorganisms in BWTSs, and they form the core of a microbial ecosystem. Nitrifies (ammonia- and nitrite-oxidizing bacteria, AOB and NOB), polyphosphate-accumulating organisms (PAOs), glycogen-accumulating organisms (GAOs), and typical heterotrophic organisms are all microorganisms found in BWTSs (OHOs). BWTSs also contain a variety of viruses and higher microorganisms (such as protozoa and metazoan). The microbial ecosystems of BWTSs are made up of these organisms.
Endogenous processes are microbial cells’ internal metabolic processes and interactions, such as endogenous respiration/cell maintenance, cell decay, death-regeneration/cryptic growth, bacterial predation by higher microorganisms, as well as cell lysis caused by virus infection or poor environmental conditions (pH, toxic substances, temperature and others).
Endogenous processes are divided into two categories: cell-level and community-level. In Figure 1, the relationships between these two levels are depicted.
Cell Level: To maintain its integrity and activity, each microorganism requires a specific quantity of energy (i.e., so-called cell maintenance energy). To create energy for cell maintenance, a portion of substrate from either external or internal sources must be oxidized. However, in endogenous processes, cell maintenance energy is derived from within the cell.
- Community Level: Microorganisms are frequently exposed to harsh environmental circumstances (pH, poisonous chemicals, temperature, and so on) that can cause cell death and lysis. Viral infection can also cause cell death and lysis. Furthermore, because to the presence of higher microorganisms, bacteria in BWTSs are under predation pressure. All of these activities take place at the same time in the community and result in a reduction in the number and/or activity of bacteria in BWTSs.
It is necessary to investigate the influence of BWTSs on maintenance energy. The impact of alternate anaerobic, anoxic, and aerobic settings, for example, should be investigated since it is vital to understand why PAOs and GAOs’ maintenance ATP consumption rates (mATP) are lower under anaerobic conditions. Furthermore, the impact of growth rate, SRT, and the fraction of inactive biomass is unknown.
Different decay processes (starvation, viral infection, and predation) should be quantified and expressed independently in the total decay of bacteria. The impact of BWTS operation parameters should also be determined.
To determine cell decay rates, several new or modified approaches are required. It’s important to distinguish between cell decay caused by bacteria’s reduced activity and cell decay caused by bacterial lysis and death. Furthermore, laboratory batch reactors differ from BWTS aeration tanks, therefore extrapolating decay rates reported in batch tests to full-scale systems has been questioned.
Biomolecular techniques such as FISH and chemical fluorescence staining techniques such as Live/Dead are useful for obtaining the total bacteria and active bacteria compositions in BWTSs and seeing their changes during the decay process. However, the unpredictability of these technologies’ quantifications may limit their widespread implementation.
The composition of inert material in BWTSs, as well as the impact of operating parameters on the degree of inertness, should be investigated further, as should the exact fraction of inert material have created in endogenous processes.
The maintenance procedures of AOB and NOB, particularly under starving conditions, should be the subject of a basic investigation. The precise methods by which nitrifies cope with starvation must be understood, as well as the precise energy sources utilized for cell preservation under famine conditions. To give a more accurate prediction of BWTS working conditions, existing models should be updated with additional knowledge about endogenous processes.
Biological Wastewater Treatment Systems Frequently Asked Questions
1) How does biological water treatment work?
Microorganisms in biological reactors are used in biological wastewater treatment to clean wastewater. The organic materials and nutrients present in the wastewater are assimilated by these bacteria for their growth while also being removed by them.
2) What is the purpose of biological treatment?
Additionally, biological treatment can be utilized to produce biogas for energy purposes, destroy human diseases, and reduce the volume of waste materials. Both aerobic and anaerobic operating methods can be used for biological treatment. The aerobic breakdown of hazardous substances and biodegradable organic waste called composting.
3) What is the basic principle of a biological sewage treatment plant?
Decomposition of the raw sewage is the fundamental operating concept of a biological treatment facility. The sewage chamber is aerated with fresh air to complete this procedure. The raw sewage that can be dumped in the sea is broken down by aerobic bacteria that can exist on this clean air.
4) What is the process of biological wastewater treatment?
The conventional approach, commonly referred to as the biological wastewater treatment method, is a popular and frequently utilised type of treatment. It considers biodegradation bleaching with the help of various microorganisms, including fungi, bacteria, yeasts, and algae.
5) What are the methods used for biological treatment?
Bioremediation and phytoremediation are the two main technologies used in biological therapies. The process of bioremediation takes advantage of microorganisms’ capacity to break down and purify organic pollutants. The two general strategies of bio stimulation and bioaugmentation are frequently employed.