South Africa, a third-world country, is challenged by its water treatment techniques. This poses a technological, operational, and economic challenge for water treatment facilities.
South Africa is currently experiencing a difficult economic landscape. For 2024, the projected GDP growth is approximately 1.2 percent, a slight improvement from the previous year's growth of below 1 percent.
Despite these challenges, South Africa remains a significant player in the Southern African region, which is expected to see a modest increase in growth. The population is seeing a brisk annual growth rate for 2024.
Wastewater treatment poses a significant challenge for a country grappling with both economic and growing population pressures.
So how does wastewater treatment focus its resources in this difficult environment?
The conventional technique to measure microorganisms in water, called Biochemical Oxygen Demand (BOD), is also referred to as the BOD5 measurement. It is a test that determines the amount of oxygen consumed by microorganisms while decomposing organic matter in a water sample over a 5-day incubation period at 20°C. This test is widely used as an indicator of organic pollution in water, as it measures the amount of biodegradable organic material present, reflecting the strength of wastewater or the level of pollution in a natural body of water. The BOD5 value is typically expressed in milligrams of oxygen per liter (mg/L).
The conventional BOD5 measurement involves collecting representative water samples and, if needed, diluting them to ensure sufficient dissolved oxygen. If the sample lacks enough microorganisms, an inoculum is added. Buffers and nutrients are included to promote microbial growth. The initial dissolved oxygen (DO) concentration is measured, and the sample is incubated at 20°C for five days in darkness. The final DO is measured afterwards. The BOD5 value is calculated by subtracting the final DO from the initial DO, indicating the level of oxygen consumption due to organic matter.
This process takes about five days, is usually outsourced, and is expensive to operate. However, new technologies may address these issues and alleviate some of the pain points in the process.
Thomas Ingwani is a doctoral student at the University of South Africa. He recently co-authored a paper, An optimized and validated surrogate analyte A‑TEEM–PARAFAC–PLS technique for detecting and quantifying the biological oxygen demand in surface water, that confirmed a cheaper, faster, and more accurate optical technique that is revolutionizing wastewater treatment in the United States.
“A 5-day test duration makes BOD5 measurement unsatisfactory and hinders the development of a quick technique,” researcher Thomas Ingwani said.
He decided to evaluate a relatively new method to address some of the limitations of conventional BOD5 measurement testing.
The method is based on a proprietary flavor of fluorescence spectroscopy. Simultaneous absorbance, transmittance, and fluorescent Excitation-Emission matrix acquisition (A-TEEM) create a molecular fingerprint of samples, correcting for the inner filter effect on the fly. This makes it concentration-independent.
Samples are collected and loaded into cuvettes, and results are delivered in 15s to 5 min, instead of the days required for the conventional BOD5 measurement. A-TEEM runs on the HORIBA Aqualog, a small benchtop instrument that can be placed inline within the water treatment testing chain.
This informs engineers quickly and accurately of how to treat the effluent at the plant level, without having to use outside, third-party services or wait days for results to come in.
Ingwani concluded that protein-like fluorescence peaks show a strong correlation between the BOD characteristics and the fluorescence intensities with A-TEEM.
“For identifying and measuring BOD in surface water, a simultaneous absorbance–transmittance and fluorescence excitation-emission matrices (A-TEEM) method combined with PARAFAC (parallel factor) and PLS (partial least squares) analyses was developed using a tyrosine and tryptophan (tyr–trpt) mix as a surrogate analyte for BOD. The use of a surrogate analyte was decided upon due to lack of fluorescent BOD standards,” the paper’s authors wrote.
The abstract discusses a new approach to measuring Biological Oxygen Demand (BOD) in water samples, instead of a 5-day test that can be cumbersome. Researchers found that certain fluorescent peaks related to proteins correlate well with BOD levels. Due to the absence of fluorescent BOD standards, a mixture of tyrosine and tryptophan as a stand-in for the BOD standard. This A-TEEM method coupled with PARAFAC and PLS techniques showed very good indicating that they can effectively detect and quantify the tyr-trypt mixes as stand-ins for BOD levels in surface water.
With excellent accuracy and reliability, this technique has the potential to replace traditional BOD testing methods, offering a faster solution for water treatment facilities. Future studies are planned to test this method on real wastewater samples from different treatment plants.
The conclusion of this paper highlights a new method for detecting and measuring BOD in surface water using a surrogate analyte, specifically a mix of tyrosine and tryptophan. This method has shown promising results, with the instrument responding sensitively to the tyr-trypt mixes as surrogate for BOD measurements. It has been validated according to established guidelines and proved to be accurate and reliable.
One major advantage of this the standard addition method is its ability to correct for any effects caused by the sample's matrix. While this method won't completely replace more detailed chemical analyses, it could help flag samples that require further testing. Overall, further studies are needed to explore this method's application in various wastewater samples from different treatment plants.
This study is likely to transform the practices of scientists interested in measuring BOD in water. The method is efficient, demands minimal sample preparation, and is simple to perform. Additionally, it is more economical than the BOD5 measurement, which is another significant benefit of the technique.
Ingwani et al. propose a tyr-trypt mix standard as a suitable substitute for the BOD standard in water analysis.
The challenges of PLS regression were resolved through the application of the SIMPLS algorithm, which is esteemed as the most efficient and rapid PLS regression method available.
BOD denotes the level of organic pollution found in aquatic ecosystems. It assesses the quantity of organic matter that can be broken down by aerobic bacteria in diverse environments, including sewage, soils, sediments, waste, and sludge. A high BOD level reflects a substantial degree of organic pollution in the water, which enables plant operators to create strategies for the removal and treatment of the significant organic matter present. Conversely, a low BOD level indicates a smaller amount of organic material, leading operators to adjust their methods to address this lesser quantity. The dosage of treatment chemicals may be adjusted accordingly Ingwani et al.
Ingwani et al., indicated that this method has the potential to be scaled up for large-scale wastewater treatment operations.
According to Adam Gilmore of HORIBA, who is also a coinventor of the A-TEEM spectrometer, the analysis of a sample using the BOD5 method incurs a cost of approximately $50. In contrast, the expense associated with analyzing a sample through A-TEEM spectroscopy is around $5, benefiting from a more straightforward sample preparation process.
One notable benefit of obtaining absorbance spectra and 3D EMMs simultaneously is the unique correction of inner-filter effects, resulting in a more accurate interpretation of the spectral data.
Gilmore has been appointed at the University of South Africa as an equivalent of a visiting professor.
Thabo Nkambule, Ingwani’s academic advisor and mentor, is a member of the ASTM Organics Committee for Water Quality.
And there's oftentimes discussions of this BOD5 technique, and there are plans to phase this out, primarily because it relies on an inoculum of bacteria at the initial stages.” Nkambule said. “You know, from there they monitor the consumption of oxygen, but that inoculum can vary widely in terms of activity and based on the source and how long it's stored and other things like that. So it's a pretty crude measurement. So what we're bringing to the table is a much more precise optical visualization of the components that are causing this. So, it's more of a WYSISYG because BOD5 you don't see anything except the oxygen concentration reading. And here (with A-TEEM fluorescence spectroscopy), we see the components that are responsible for digesting the organic matter and, and oxygen.”
The partnership with HORIBA and the University of South Africa continues to grow.
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