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Anaerobic System More Effective For Treatment Of Livestock Wastewater-UPM

4 January 2023

KUALA LUMPUR, Jan 4 (Bernama) – Case 1: In October last year, eight Department of Veterinary Services Malaysia (DVS)-licensed pig farms were identified as the source of the foul-smelling wastewater discharged onto the coast at Tanjung Sepat in Kuala Langat, Selangor.

Case 2: Last September, the Ministry of Environment and Water issued a notice to DVS directing it to monitor pig farms said to be causing pollution to Sungai Rambai in Lukut, Port Dickson, Negeri Sembilan.  

The above two were among a number of water contamination cases reported last year with the cause of the pollution traced to livestock farms and abattoirs, including those involved in slaughtering chickens and cows, whose unsustainable operations have resulted in the discharge of effluents and untreated animal faeces into the sea and rivers.   

People need to maintain the sustainability of the river so that it is not polluted by waste materials such as plastic and industrial waste so that the river can be used by future generations. --fotoBERNAMA (2023) All RIGHTS RESERVED

In fact, livestock slaughterhouses have been identified as among the industries that use huge quantities of raw water and produce an equally substantial amount of wastewater “rich” in pollutants and pathogens.

In 2004, the United States Environmental Protection Agency classified slaughterhouse wastewater as one of the most hazardous wastes released into the environment as it is known to house a large number of harmful organic microorganisms.

In Malaysia, a group of researchers from the Faculty of Engineering, Universiti Putra Malaysia (UPM), recently carried out a special study to determine to what extent untreated wastewater from abattoirs can harm the environment. Associate Prof Dr Mohd Razif Harun, a researcher at the Department of Chemical and Environmental Engineering in the Faculty of Engineering, UPM, also participated in the study.

Among other things, the team found that the anaerobic wastewater treatment system has considerable advantages over the conventional aerobic system as the former yields methane gas, a biogas that has the potential for use as an alternative energy source, and high-quality effluents that can be turned into biofertilisers.



A resident showed among the rice paddies that have been damaged due to pig waste pollution in a river in his village. --fotoBERNAMA (2023) ALL RIGHTS RESERVED

Head of the UPM research team Associate Prof Dr Syazwani Idrus told Bernama the samples of untreated wastewater used in their study were taken from a local cattle slaughterhouse and they revealed elevated chemical oxygen demand (COD) and biological oxygen demand (BOD) values.

COD and BOD are the two parameters that test the oxygen-demanding strength of wastewater. COD is the amount of oxygen that is required for the chemical oxidation of the organic and inorganic chemicals present in the wastewater while BOD is the amount of oxygen demanded by the microorganisms in the wastewater for the decomposition of biodegradable matter under aerobic conditions.

For example, the high concentration of a COD pollutant in a sample shows it contains a high amount of organic matter that cannot be oxidised.

“If this is the case, the level of oxygen that dissolves in the water is also lower and this is harmful to the environment especially aquatic life,” Syazwani said.

She said this will also defeat the real purpose of treating wastewater which is to cut down its high COD level.

“This is why researchers are of the opinion that aerobic wastewater treatment methods are less efficient in terms of their costs as well as technical and practical aspects,” she added.  

Assoc Prof Dr Syazwani Idrus

Elaborating on the wastewater samples tested by her team, Syazwani said they were tested to see their potential in producing biochemical methane gas as well as to check the presence of other organic matter considered hazardous if discharged into river water sources.

“Before that, we have to understand that the real reason for treating wastewater is to prevent environmental pollution as well as prevent the emission of methane gas (CH4) which is one of the greenhouse gases responsible for the serious issue of global warming,” she said.

According to many environmental experts, greenhouse gas emissions are linked to the uncontrolled degradation of organic matter found in the increasing amount of industrial wastes produced by human activities, she added.

“Among the main issues we see in the conventional system of treating wastewater produced by farms and slaughterhouses is the use of the aerobic treatment system where waste-feeding microorganisms that consume a lot of oxygen are used to treat wastewater.

“This treatment process requires the use of a lot of oxygen, thus pushing up the operational costs (of the farm/abattoir operators). Furthermore, the treatment process itself is quite lengthy. Researchers are worried about this as the problems may cause some operators to discharge their wastewater without treating it first,” she said.  

Syazwani added that the low awareness of environmental protection, as well as a low understanding of environmental laws and policies, are among the other reasons livestock farm and abattoir operators are not concerned about wastewater treatment.   



An anaerobic machine known as a modified UASB reactor can process untreated wastewater that can be used as a renewable energy source in the form of methane gas production. --fotoBERNAMA (2022) ALL RIGHTS RESERVED/ MUHAMMAD BASIR ROSLAN


The UPM research team, meanwhile, also tested the anaerobic wastewater treatment method and found that it was more effective in producing high-quality effluents and beneficial biogas.

According to Syazwani, they used a modified Upflow Anaerobic Sludge Blanket (UASB) reactor to treat the slaughterhouse wastewater taken from their samples.

“Among the advantages of this system is that the waste-eating microorganisms do not use oxygen. The treatment costs are also lower than that of the conventional system because it (anaerobic system) doesn’t require the use of an oxygen compression machine,” she explained.

She said the use of the UASB reactor also results in the production of methane gas which can be used as an alternative energy source.

She also said that the presence of fats, oils and grease (FOG) in wastewater is recognised as one of the main components contributing to BOD and COD which reflect the waste’s high potential as a biogas source.

“Most European countries make use of the anaerobic wastewater treatment system. It can also be used to treat food waste and agricultural waste,” she added.

Pointing out that the UPM researchers don’t regard all untreated wastes as useless, Syazwani said the latter has the potential to be processed into high-quality effluents as well as methane gas which can be used as an alternative energy source.

“Even though livestock farm and slaughterhouse wastewater is harmful to the environment and has high levels of COD and BOD, it can be processed and used as a renewable energy source in the form of methane gas,” she added.

According to the website ourworldindata.org, in 2019, about 64 percent of electricity consumed worldwide came from fossil fuels. This has negative repercussions as the burning of fossil fuels to produce electricity produces carbon dioxide which is one of the main drivers of climate change.  



The research group from UPM is also developing a Modified CSTR semi-solid food waste treatment system that has the potential to produce methane gas as an alternative source of electricity and biofertiliser. --fotoBERNAMA (2022) ALL RIGHTS RESERVED/MUHAMMAD BASIR ROSLAN

Syazwani, meanwhile, said her team is developing a system known as the Modified Continuous Stirred Tank Reactor (CSTR) to treat food waste and semi-solid livestock faeces and process them into methane gas and biofertilisers.

According to her, the use of CSTR is seen to be more holistic as its configuration allows it to treat semi-solid waste such as cow dung. The machine can also turn digestate (the material remaining after the anaerobic digestion of a biodegradable feedstock) into biofertilisers.

Syazwani said Tenaga Nasional Bhd, through TNB Research Sdn Bhd, has shown an interest in the CSTR and has extended a research grant of RM400,000 to the UPM research team to help in its efforts to improve the quality of treated semi-solid waste, such as food waste, which can be developed into an alternative energy source to generate electricity.

To improve the quality of the anaerobic waste treatment, animal waste can be subjected to biodegradation together with other types of waste including food waste in order to improve the carbon and nitrogen ratios and balance the sugar content in the waste concerned.   

The CSTR can also be used in dry anaerobic digestion which, at the same time, will reduce the volume of the treated waste produced.

“All stakeholders in the livestock and food industry must see the potential of this system in view of the high demand for renewable energy at the national and international levels,” she added.


Translated by Rema Nambiar  




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