Review of Anaerobic Baffled Reactor for Treatment of Industrial Wastewater in Nigeria

Abstract

Industrialization, although with its gain has also led to environmental degradation. One of such degradation is pollution. Water we know is essential to life but with industrialization, the existence is being greatly threatened. The need to treat wastewater has become incontrovertibly important as man’s activities in the environment has depleted the limited available water sources daily. These activities include indiscriminate discharge of untreated wastewater into neighboring water bodies thereby causing pollution to the environment and aquatic life. For years, conventional wastewater treatment processes have been adopted and found reasonably successful in treating effluents from wastewater in order to meet the required standard before discharge. The review of the anaerobic baffled reactor (ABR) in the management of industrial wastewater is done in this chapter. The review considers the use of ABR in Nigeria for the treatment of industrial wastewater. The ABR’s basic principle, applications, merits, demerits and challenges (in Nigeria) is addressed.

1. Introduction

Water is classified among the requisite renewable resources for food production, economic advancement, maintenance and general well-being of all living things. Most of the uses of water are impractical to replace, difficult to clean and expensive to transport. Also, water is one of the most manageable natural resources as it can be diverted, stored, recycled and stored [1]. The accessibility of freshwater that is free from pollution is a simple necessity for any growth of humans, however, the obtainability of such water that is unpolluted and usable is limited. In various rural areas of developing nations, the predominant factor contributing to water pollution is the unrestricted discharge of untreated sewage directly into nearby bodies of water [2].

With economic growth and industrialization, water resources are growing progressively scarce. The condition of the world environment is frequently becoming of poorer quality in most areas. Treatment, management and disposal of industrial effluent is currently one of the most hazardous sources of environmental problems. This reason brings an urgent need to create reliable and efficient technologies for wastewater treatment.

Wastewater treatment can be described as the planning and conversion of wastewater and associated outputs for reuse (secure and free from danger to the environment) or discarding in-order to mitigate health hazards and protect the environment from the detrimental impacts of pollution, it is essential to address and eliminate significant variables such as solids in wastewater, biological oxygen demand, chemical oxygen demand, pathogenic microorganisms, and nutrients. Other impurities that are of importance to be treated to mitigate their harmful effects include heavy metals or persistent organic compounds (POPs).

This dire need to treat wastewater has led to different researches about different methods of treating wastewater. Of the many methods discovered for the treatment of wastewater, the anaerobic process for wastewater treatment has continued stand out in all the various methods of waste water treatment. This method of treatment has advantages such as simplicity of design, high treatment efficiency, use of non-sophisticated equipment, little excess sludge is generated and capital and low operating cost [3, 4, 5].

The Anaerobic baffled reactor (ABR) is described as one of the high-level anaerobic reactors, it has been largely used in the treatment analysis of wastewater (both industrial and domestic). According to [5, 6, 7], the ABR was originally developed at Stanford University. The ABR functions much like anaerobic sludge blanket reactors (UASBs), utilizing a system of vertically positioned baffles that guide the wastewater to move both below and above them from the inlet to the outlet. This design ensures that the effluent comes into close contact with a substantial quantity of active biomass, whilst maintaining a comparatively low concentration of biological solids in the effluent. With regards to the advantage, an essential benefit of the ABR lies in its capacity to segregate acidogenesis and methanogenesis along the length of the reactor [5, 8]. This enables distinct bacterial populations to thrive in their respective compartments, with acidification prevailing in the initial section and methanogenesis dominating in the subsequent section [5, 8]. As reported [6, 9, 10], either the industrial or domestic wastewater can be effectively treated using the ABR. The rate of chemical oxygen demand (COD) elimination in ABR is stated to be between the scale of 70–90%. While the rate of elimination of the biological oxygen demand (BOD) is stated between 60–85%. The rate of removal for total Suspended Solids (TSS) is up to 90%.

Nigeria is contending with significant challenges when it comes to management of wastewater management, some of the factors responsible for this include rapid urbanization, population growth, and inadequate infrastructure which has culminated into pressing wastewater crisis [11, 12]. Sustainable ecological development and public health is endangered by contaminated water sources, indiscriminate and unrestricted dumping of untreated wastewater in the environment, and scarce sanitation facilities have all contributed to environmental diseases and ecological deterioration [12]. As stated by [12], some of the identified steps to be taken to mitigate against the challenge of wastewater management in Nigeria include investment in infrastructural development which will include modern treatment plants, sanitation facilities and functional and well-maintained sewer system; also, engaging the communities will be beneficial to the management of wastewater as each community can monitor her environment. Environmental policies and regulations should be developed and stringent measures put in place to check defaulters. Other identified measures are capacity development through education and training for wastewater management professionals, innovation and technology which has become the main hub of wastewater treatment in the advanced countries.

2. Sources and characteristics of wastewater in Nigeria

Like many countries of the world, the sources of wastewater in Nigeria are from domestic usage (cleaning, washing, bathing, flushing); industrial manufacturing processing (cleaning, washing, extraction) and agricultural processes (washing and cleaning). The wastewater from industrial manufacturing processes can either be large scale manufacturing processes which in most cases are automated or non-large-scale industries which are most times cottage industries like the starch processing industry, slaughter houses, garri processing factories, etc. These spent waters from sewage (domestics use) and other wastewater effluents (industrial manufacturing processes) have different and varying characteristics. The characterization is done according to the physical, chemical and biological constituent (composition) of the wastewater. These characteristics include high BOD and COD (depending of the source of the wastewater and the pollutant load), pH level which usually vary from acidic to basic (depending on the source). Others are total solid, dissolved solid, suspended solid, nitrogen, phosphorus, chloride, alkalinity which in all cases usually vary from strong concentration to low concentration depending on the processing resulting to the wastewater. It has been observed that in most cases, these characteristics usually exceed the limits set by standard organizations like World Health Organization, Federal Environmental Protection Agency, etc. and therefore, before discharge or disposal of the wastewater into the environment, there is need to treat the it which in most cases is usually a water body. Table 1 shows the characteristics of raw industrial wastewater as reported by [13]; the values exceed the standards given for safe discharge into the environment.

Parameters	BOD5, mg/L	COD, mg/L	TSS	pH
Brewery	1609.34–3980.61	1096.41–8926.08	530.67–3728.02	4.6–7.3
Abattoir	476–3850	935–6600	750–4400	6.85–8.19
Cane Sugar	350–2750	1000–4340	760–800	5–6.5
Oil refinery	100–500	150–800	130–600	2–6
Coke oven	510–1360	930–3120	19–3330	6.8–8.2
Tannery	1000–2000	2000–4000	2000–3000	11–12
Textile	50–500	250–8000	100–700	5.6–9

Table 1.

Characteristics of raw industrial wastewater [13].

3. An overview of wastewater treatment practices in Nigeria

The treatment of wastewater in Nigeria is vital to environmental sciences and public health. Common practices vary depending on the place regulatory bodies available, finances available, etc. Wastewater is something virtually every industry or household releases. Over the years in Nigeria, most industries and households have been making use of some very poor treatment practices for wastewater due to ignorance of the dangers it poses to our ecosystem. The Government has been trying to put things and agencies in place to monitor and ensure compliance by industries, households, and offices. The agencies have only been up and doing in terms of ensuring large-scale industries comply, most small and medium-scale industries end up finding their way by evasion.

Some households just channel their wastewater into the drainage system in front of their house or on the road when a drainage system is absent. This is the most familiar wastewater disposal technique used in most rural areas and some urban areas. This is because of its cost-efficiency. It is virtually the cheapest wastewater disposal method. Most small and medium-scale industries make use of this wastewater disposal method. It poses a great risk to the environment because it has a net effect on global warming also this wastewater is eventually disposed of in oceans and water bodies which causes a great risk to aquatic lives and the ocean’s sanity. One of the major reasons why this method is used is because of the absence of a central sewage system as present in other developed nations of the world.

The most important aim of treating wastewater is to eliminate from the wastewater (to permissible limit) the solids (suspended as well as dissolved) present therein. The purpose of this process is to enable the discharge of the remaining treated wastewater into the receiving water without compromising its optimal or intended use. The solids extracted from the wastewater primarily consist of organic matter, although they may also encompass inorganic solids. The sludge removed from the wastewater (in the form of solids and liquids) are also treated. Also, the odor is controlled and pathogenic organisms in the wastewater are expelled through relevant methods of treatment. The above reasons inform the main aim of waste-water treatment [14]. Some of the wastewater treatment practices in Nigeria include.

3.1 Aerobic treatment of wastewater

Wastewater undergoes aerobic method of treatment in the presence of oxygen. Within aerobic wastewater treatment systems, aerobic organisms utilize oxygen to convert organic compounds in the wastewater into carbon dioxide and generate new biomass. This method exclusively relies on the use of air for wastewater treatment. In contrast to conventional septic tanks, aerobic treatment systems demonstrate enhanced efficiency in breaking down organic matter, accelerating the decomposition of organic solids, and diminishing the concentration of pollutants [15].

3.2 Physio-chemical treatment of wastewater

Physicochemical treatment is a commonly used method in the treatment of wastewater. It is applied to remove heavy metals, oils, suspended matter, greases, toxic pollutants, high salt concentrations, dissolved organic substances, as well as organic and inorganic components that are difficult to decompose, and phosphorus. Physicochemical treatment is used as pre-treatment, final treatment, and specific treatment for wastewater recycle as process water. The techniques used in physicochemical treatment include dilution, sedimentation, and other methods [15].

3.3 Physical treatment of wastewater

This is a common method used in treating wastewater in Nigeria. It involves processes like sedimentation, screening, and skimming which are used to remove solid particles. This method involves no chemicals; hence it is a chemical-free process.

Sedimentation is among the most common physical techniques used for treating wastewater. It involves suspending the insoluble or heavy particles in the water, and allowing them to settle at the bottom over a period of time, and then separating the pure water from the sediment. Aeration is another effective physical water treatment technique that involves circulating air through the water to make available oxygen to it. This helps to break down organic matter and remove unpleasant odors. Finally, filtration is used to filter out impurities and particles that are not soluble present in the wastewater. Sand filter which is the most commonly filter used for this purpose. Additionally, grease found on the surface of some wastewater can be easily removed through this filtration method [16].

3.4 Anaerobic treatment of wastewater

Unlike aerobic treatment of wastewater, anaerobic wastewater is treatment of wastewater without the presence of oxygen. The whole process of anaerobic treatment occurs in the absence (devoid) of oxygen. The whole process is very effective in removing biodegradable organic compounds leaving mineralized compounds in the solution [17]. Different industries majorly use anaerobic method of treating wastewater because of its suitability and the basic requirement. Table 2 shows the summary of the advantages and disadvantages of the anaerobic treatment of different types wastewater. In anaerobic environments, the decomposition of organic matter occurs through the successive and cooperative metabolic interactions among different trophic groups of prokaryotes. These groups include fermenters, acetogens, methanogens, and sulfate-reducing bacteria (SRB) [18]. The metabolic interplay among these microbial groups results in the conversion of intricate organic compounds into simpler substances, including ammonia, hydrogen sulfide carbon dioxide, and methane [18].

Advantages

High efficiency: the system exhibits good removal efficiency even under high loading rates and at low temperatures.

Simplicity: both the building and set-up (operation) of anaerobic reactors are somewhat straightforward.

Flexibility: anaerobic means of treatment can be effortlessly applied on a wide scale, ranging from small to large systems.

Low energy consumption: the reactor’s energy consumption is minimal, as it does not require heating up of the influent to attain the operational temperature, and all processes can be driven by gravity.

Energy recovery: the process yields energy in the form of methane, contributing to energy sustainability.

Low sludge production: the system generates a small volume of sludge that is well-stabilized and exhibits favorable dewatering properties.

Low nutrient and chemical requirement: anaerobic treatment, particularly in sewage treatment, often necessitates minimal or no chemical additives. In this context, a sufficient and consistent pH level can be sustained without the need for the introduction of chemicals.

Disadvantages

Low removal of pathogen and nutrient: the removal of pathogens and nutrients is relatively limited in anaerobic treatment, as it is only partial. Consequently, additional post-treatment is necessary to achieve the desired level of removal.

Long start-up: the anaerobic treatment’s low startup is attributed to the slow (gradual) rate of growth of the methanogenic organisms, resulting in a prolonged startup period.

Possible bad odor: the production of hydrogen sulfide occurs, necessitating careful management of biogas to prevent unpleasant odors.

Necessity of post-treatment: in order to meet the prescribed standards for the discharge (into the environment) for the organic matter and pathogens, post-treatment of the effluent from the anaerobic process is usually deemed necessary.

Table 2.

Advantages and disadvantages of using anaerobic method of wastewater treatment.

Source: [18].

3.5 Reverse osmosis treatment

Reverse osmosis (RO), a filtration technique that makes use of a special membrane to remove significant molecules and ions from solutions. To achieve this, it is done by the application pressure to the mixture on one side of the membrane. The membrane allows smaller parts, such as the solvent, to go through it freely, while retaining the solute on the pressurized side. To work effectively, the membrane must have small pores that do not allow large molecules or ions to move through. It is interesting to learn that reverse osmosis membranes have a compressed obstruction film in the polymer matrix which is responsible for most of the separation. This film is only intended to permit water to go through although disallowing the passage of solutes like salt ions. To achieve this, a high pressure of 2–17 bar (30–250 psi) is exerted on the high concentration side of the membrane for fresh and brackish water, and 40–70 bar (600–1000 psi) for seawater, overcoming its natural osmotic pressure of around 24 bar (350 psi) [14].

These practices named above are some of the wastewater treatment practices carried out in Nigeria, the method used vary from place to place and also depend on some factors such as finance available, volume of water treated etc. It all has a single aim, which is getting untreated water treated for reuse or for safe disposal.

4. Emerging technologies for wastewater management in Nigeria

Wastewater management involves collecting, treating, and reusing wastewater to protect water resources, promote environmental sustainability, conserve resources, and safeguard public health. Before the advent of modern technologies, wastewater management relied on simpler and often less efficient techniques. While some of these methods are still used in certain contexts, advancements in science and technology have led to the development of more sophisticated and effective wastewater treatment processes [19]. Some traditional or old wastewater management techniques include; Imhoff tanks (sedimentation tanks) that allow solids to settle at the bottom while liquids move to the upper chamber, septic tanks, open-air lagoons, chemical coagulation, and flocculation. Although old wastewater management techniques have been useful in catering to basic sanitation needs, they often do not meet current environmental standards. Fortunately, the advancements in technology have resulted in more efficient and eco-friendly treatment methods, which ensure better protection of water resources and public health [13].

4.1 Advanced biological treatment

1. Membrane bioreactors: membrane systems have become essential in separation processes, adding new techniques to more traditional processes. Recent developments in membranes have made it possible to achieve design objectives with added flexibility and improved efficiencies [20]. Examples of such innovations can be discovered in membrane bioreactors, seawater desalination, batteries, super-capacitors, solar cells, and microbial fuel cells, which have led to outstanding results.

2. Anammox (anaerobic ammonium oxidation): anaerobic ammonium oxidation is the process of converting ammonium to di-nitrogen gas by means of nitrite equally as an electron acceptor. This biological process removes nitrogen compounds from wastewater more efficiently, reducing the need for energy-intensive nitrification and denitrification processes.

4.2 Resource recovery

1. Phosphorus and nutrient recovery: the reclamation and recycling of nitrogen and phosphorus is extremely important and thus required. With the use of nitrogen- and phosphorus-based synthetic (inorganic) fertilizers, there is a rising trend, and large-scale influx of responsive nitrogen in the atmosphere; this comes with severe health consequences on humans and the environment. Contrary, phosphorus, a non-renewable means of resource, faces a grave threat of depletion. As a result, the retrieval and reuse of both nitrogen and phosphorus is greatly required. There are multiple ways to recover nitrogen, including ion exchange and absorption, bio-electrochemical systems, and air stripping of ammonia. Similarly, there are various methods for phosphorus recovery, such as physical filtration and membrane processes, chemical precipitation, high-temperature acid hydrolysis, biological assimilation, physical-chemical absorption and ion exchange. On Earth, nitrogen and phosphorus play vital roles as macronutrients supporting life. Nevertheless, it is imperative to extract them from waste streams to effectively counteract the potential eutrophication of water-receiving bodies [21].

2. Biogas and energy generation: the reduction in the availability of energy resources and the costs of energy costs have brought about a crucial and critical point of worry for decision-makers and also users about their societal activities, environmental and economic impact. This shift has led wastewater management experts to reconsider wastewater treatment plants (WWTPs) as essential contributors to a bio-based circular economy, rather than viewing them solely as facilities for end-of-life treatment and disposal [5]. Consequently, redesigning and operating modernized wastewater treatment plants has been identified as an important way for resource utilization and energy recovery in wastewater locations. Efficient capture and management of sludge generated at WWTPs have the potential to generate significant energy in the form of biogas, potentially transforming WWTPs into net energy producers rather than consumers [22].

4.3 Decentralized wastewater treatment

This refers to a method of managing wastewater at the location where it is generated, rather than relying on a central sewage treatment plant. These systems such as modular treatment units and containerized plants are gaining more attention due to their potential to provide efficient and sustainable solutions for managing wastewater in various settings [23]. Centralized wastewater collection and treatment systems are costly to build and maintain, particularly in regions with low population densities and scattered households. Developing nations face challenges in securing the necessary funds for constructing centralized facilities and acquiring the technical expertise to effectively manage and operate them. Consequently, decentralized systems emerge not only as a sustainable solution for small communities in the long run but also as a more dependable and cost-effective alternative [24].

4.4 Advanced oxidation processes (AOPs)

In the 1980s, the concept of advanced oxidation processes (AOPs) was first presented for the treatment of potable water. AOPs are defined as oxidation processes that produces a sufficient amount of hydroxyl radicals (OH·) to purify water. Over the years, the concept of advanced oxidation processes (AOP) has evolved to encompass oxidative methods utilizing sulfate radicals (SO₄⁻). Unlike conventional oxidants like chlorine and ozone, which serve a dual purpose of decontamination and disinfection, AOPs are primarily employed for the eradication of organic or inorganic contaminants in water and wastewater [25].

It is important to understand that the efficiency of various technologies used to treat industrial wastewater may differ based on the certain characteristic constituent of the wastewater and the regulatory requirements of the industry. Moreover, continuous research and development in this field may result in the discovery of newer and more effective technologies.

5. Anaerobic baffled reactor

The anaerobic baffled reactor (ABR) represents the third generation of anaerobic bioreactors, distinguished by its specific design incorporating a series of vertical baffles within the reactor [26]. Originating from Stanford University in 1983, McCarty and colleagues developed the ABR, conceptualizing it as a sequence of up-flow anaerobic sludge blanket reactors (UASBS), characterized by multiple compartments [8, 27, 28]. Typically, a conventional ABR consists of vertically positioned baffles that guide the wastewater both under and over them as it traverses from the inlet to the outlet. This unique flow pattern minimizes bacteria washout, allowing the ABR to maintain an active biological mass without relying on fixed media.

The gas production in each reactor section leads to the upward movement and settling of bacteria, creating a relatively slow horizontal flow down the reactor. This results in a Sludge Retention Time (SRT) of 100 days at a Hydraulic Retention Time (HRT) of 20 hours. The deliberate slow horizontal movement ensures intimate contact between wastewater and the active biomass during its passage through the ABR, even with short HRTs ranging from 6 to 20 hours [8, 29]. Additionally, the ABR can be operated with granules or internal media to enhance stability. This separation of Sludge Retention Time (SRT) from Hydraulic Retention Time (HRT) contributes to effective removal of chemical oxygen demand (COD) and solids, low sludge production, and a compact footprint [28].

Thanks to the design of ABR, the reactor exhibits resilience to equally severe hydraulic and organic shock loads yet not compromising performance. As a result, it is gaining widespread use in many developing countries as a cost-effective and effective solution for low-cost sanitation and treatment of industrial wastewater. Furthermore, it often offers the added benefit of energy production [28].

Figure 1 provides a detailed schematic representation of the ABR.

Figure 1.

Diagram of 8-compartment pilot-scale anaerobic baffled reactor with opened section showing internal baffle set up.

The treatment efficiency of anaerobic baffled reactors (ABRs) typically falls within the range of 65–90% for chemical oxygen demand (COD) removal, equivalent to approximately 70–95% biological oxygen demand (BOD) removal [30, 31]. In the initial sedimentation chamber of the ABR, a significant portion of settleable solids, representing around 50% of the total volume of total suspended solids (TSS), is removed [31]. The unique design allows for enhanced treatment of non-settleable solids, achieving a total suspended solids (TSS) removal of up to 90% [31]. The series arrangement of tanks facilitates the digestion of challenging-to-degrade substances, primarily in the rear part after the digestion of easily degradable materials in the front part [31]. Consequently, recycling of effluent could adversely impact treatment quality. ABRs can be designed to accommodate daily inflows ranging from a few cubic meters per day to several hundred cubic meters per day [31, 32]. The hydraulic retention time (HRT) in ABRs is relatively short, varying from a few hours to two or three days [30, 31, 32].

The ABR boasts numerous advantages, including a simple design, absence of moving parts, no need for mechanical mixing, cost-effectiveness in construction, high void volume reducing clogging, minimal sludge bed expansion, low HRT, stability against hydraulic shock loads, prolonged operation without sludge wasting, resilience to organic shocks, low capital and operating costs, low sludge generation, high Solids Retention Times (SRT), and minimal maintenance requirements [32]. However, there are some drawbacks to consider, such as a lengthy start-up phase, the necessity for expert design and construction, limited reduction of pathogens and nutrients, the need for further treatment or appropriate discharge of effluent and sludge, the requirement for a strategy for fecal sludge management (effluent quality deteriorates rapidly without regular sludge removal), and the absence of clear design guidelines [31].

6. Case study of the anaerobic baffled reactor

6.1 Case study I

This case study was carried out to determine the most effective method for removing organics from cassava wastewater in the Ohaji-Egbema Local Government Area of Imo State, Nigeria.

Ten anaerobic baffled reactors (ABRs) of varying sizes were constructed from 0.006 m thick stainless steel, as illustrated in Figure 2. All ABRs featured the same number of compartments to ensure proper mixing, each of the compartment is equipped with a port for sampling. Water bath was used for the maintenance of the reactor temperature at 35 ± 0.5°C, and a variable-speed peristaltic pump facilitated the pumping of the influent wastewater. Wastewater sourced from cassava processing units in Ohaji-Egbema Local Government Area, Imo State, underwent a filtration process to reduce total suspended solids to 90% before introduction into the reactor. The bioreactor operated consistently, irrespective of the loading rate, until achieving a steady-state condition. Various combinations of hydraulic retention time (HRT), influent flow rate (Q), and organic loading rate were employed during the operation of the ABRs [33].

Figure 2.

Scheme of the ABR. Adapted from [33]. 1. Feed tank. 2. Peristaltic pump. 3. Influent. 4. Sampling ports. 5. Effluent.

The research findings indicated that elevating the number of baffles from 3 to 10 led to a reduction in the inhibitor constant, decreasing from 9.9989 to 1.6101 mg/L.

6.2 Case study II

The research utilized industrial wastewater obtained from a wheat starch factory located in the central province of Iran (Ardineh Starch CO., Isfahan, Iran) as the feed for an anaerobic baffled reactor (ABR).

The experimental ABR was designed on a laboratory scale, constructed from 0.006 m thick transparent Plexiglas, with external dimensions measuring 0.53 m in length, 0.16 m in width, and a depth of 0.30 m, providing a working volume of 13.5 L. Figure 3 depicts a schematic diagram of the reactor.

Figure 3.

Schematic diagram of anaerobic baffled reactor adapted from [34]. 1. Feed tank. 2. Peristaltic pump. 3. Influent feed. 4. Flowing fluid. 5. Collection of gas. 6. Generated biogas. 7. Ports for sampling. 8. Bath for water. 9. Passage window. 10. Bed of sludge. 11. Upward flow. 12. Siphoning mechanism. 13. Mixing device. 14. Treated effluent.

The reactor comprises five equal compartments of 2.7 L each, separated by upright baffles. Each compartment includes downcomer and riser regions formed by additional upright baffles. The upcomer’s breadth is approximately 2.6 times that of the downcomer, with the lower portions of the downcomer baffles set at a 45° angle to ensure a uniform flow through the upcomer. This configuration facilitates efficient blending and interaction among the wastewater and anaerobic sludge located at the bottom of each riser. Sampling ports within each compartment enable the retrieval of biological solids and sewage samples.

To maintain a constant operating temperature of 35 ± 0.5°C, the ABR is equipped with a temperature regulator that is placed in a water bath. A variable-speed peristaltic pump (Masterflux L/S) is employed to pump the influent feed, while the outlet is coupled to a glass U-tube for level control and solids trapping. Gas produced during the process is collected through portholes in the upper part of the reactor, and its volume is determined daily using the gas-water displacement technique. The research findings indicate that the ABR effectively treats industrial wastewater from the wheat starch factory, achieving a COD removal efficiency of 61–67% [34].

7. Challenges of using ABR in Nigeria

The use of anaerobic baffled reactors for the treatment of wastewater in Nigeria presents certain potential challenges, and among them is the issue of a delayed initiation period. With the high volume of wastewater being generated, a means of treatment with slow startup time may not be considered ideal enough as faster means of treatment will be preferred. Also, as stated by [31], there are no clear design guidelines yet, this in turn brings about little or no technical know how about the design and installation of the anaerobic baffled reactor in Nigeria. In addition, it has been identified that for removal of nutrients in wastewater, additional treatment means should be added to the ABR which will result into additional cost of treatment and as result could be a challenge to the outright adoption of the ABR in Nigeria.

8. Conclusion

This chapter has reviewed the use of anaerobic baffled reactor in Nigeria for the treatment of industrial wastewater. The use of ABR in Nigeria especially for treatment of industrial wastewater is little or non-existent and as a result more research is needed to be done on the subject of anaerobic baffled reactor in Nigeria; this will in turn lead to scaling up by the industries for commercialization and real plant application.