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CHAPTERS: Chapter 1-5
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BIOREMEDIATION OF FISH POND EFFLUENT USING INDIGENOUS MICROALGAE AND BACTERIAL CONSORTIA ISOLATED FROM LOCAL PONDS IN EDO STATE.
CHAPTER ONE
INTRODUCTION
1.1 Background to the Study
The strategic role of aquaculture in the national food security and economic development programme of Nigeria has taken a new dimension and the Federal Government in its Agricultural Promotion Policy has clearly declared fish farming as one of its priority sectors in its attempts to curb the overreliance of the Nigerian economy on imported fish meat (Federal Ministry of Agriculture and Rural Development, 2021). As one of Africa’s most bountiful sources of fresh water, possessing favourable tropical climate and enjoying a long history of fish farming at a community level, Edo State has seen both commercial and subsistence aquaculture practices increase sharply over the last 10 years with catfish (Clarias gariepinus), tilapia (Oreochromis niloticus) and African knifefish as the primary species grown in eart This growth has, but, been followed by an equal growth in the amount of fish pond effluents – the nitrogenaceous, phosphorus-containing, biochemically convoluted waste effluents generated in the daily running of the usual pond management processes such as pond drainages, fishing-offings, and daily waste expulsions of surplus feeding, feces, metabolic excretions, and putrefact
The effluent of fish ponds is a problem of aquatic pollution that may not be fully recognized in the Edo State especially in the rural or peri-urban regions where fish ponds are tightly packed along the river basins, floodplains, and at the bottom of shallow valleys. The uncontrolled release of untreated or mis-treated fish pond effluent into the receiving water bodies leads to the well-characterized cascade of ecological effects: acute dissolved oxygen depletion by the significant exerted effect on biochemical oxygen demand; eutrophication Cumulative effluent loading of a series of farm adjacent fish ponds in Edo State, including the upper Ikpoba River, and Ovia River catchments has been reported to contribute to the poor water quality and reducing fish biodiversity observed in recent environmental surveys (Osagie et al., 2023).
Biological treatment methods, especially using the nutrient uptake capacity of microalgae and the mineralizing ability of organic matter of heterotrophic bacteria, provides a scientifically rational economic avenue in the treatment of fish pond effluents before discharge. Microalgae are photosynthetic, unicellular or colonial microorganisms that grow in water, incorporating inorganic nitrogen (ammonium, nitrate, nitrite) and phosphorus as essential macronutrients in forming biomass, fulfilling both goals of eliminating weapons of wastewater and producing biomass with potential valorization products in aquaculture feed, biofertilizer, and bioenergy market The biochemical transformation of dissolved organic carbon, ammonium oxidation, and nitrate reduction are driven by bacteria, especially heterotrophic degraders and nitrifying-denitrifying consortia, as the final stages of nutrient cycling pathways, which in concert with the uptake by algae can result in full nutrient removal of complex aquaculture wastewaters (Srivastava et al.,
The idea of mixed microalgae-bacteria consortia to treat wastewater, also known as microalgae-based bacterial-algal photobioreactor (MPBR) or symbiotic algal-bacteria systems, has become well-known in the literature as an effective way to exploit the metab Nevertheless, most studies regarding such consortia have been done on laboratory or industrial strains of micro-organisms developing in artificial waste waters under controlled conditions that are way way out of the physicochemical and biological complexities of natural aqueous effluents in tropical aquacultures. Research that explicitly uses indigenous microalgal and bacterial isolates that were collected in the local aquaculture ponds in West Africa, and tested their effectiveness on real-life fish pond effluents, in the local environmental conditions, is particularly missing in peer-reviewed literature.
Scientifically preferable to imported or engineered strains, indigenous associated microbial consortia should be used to treat effluents due to several reasons: indigenous organisms are already adapted to the local temperature, pH, salinity, and nutrient regimes of the treatment substrate; they are more likely to form and sustain high This paper will thus proceed to isolate, characterize and assess native microalgae and bacterial consortia in aquaculture pond in Edo State with respect to their ability to bioremediate fish pond effluent to develop the science base behind the development of practical effluent treatment systems, locally adapted to suit the Edo State aquaculture industry.
1.2 Statement of the Problem
With the intensive fish production in Edo State, volumes of nutrient-rich effluent is also produced, and it is regularly released without proper treatment into rivers, streams, and lowlands, causing eutrophication, destruction of dissolved oxygen, and pollution of the sources of downstream water supplies. Lack of affordable, technically direct-forward, and locally approved treatment technologies to the local scale and context of the Edo State fish farming activity is the nub of the problem which this study is going to discuss. Although the theoretical basis of biological treatment by microalgae and bacteria is a very pertinent approach towards managing pollution of fish pond effluent, no research has yet orchestrated systematic ways to assess the capability of native microalgae and bacterial consortia of Edo State ponds in dealing with local fish pond effluent. The gap in this research does not allow developing evidence-based treatment technologies in the sector and does not allow fish farmers or regulatory agencies to mitigate the environmental and public health impacts of untreated discharge of effluent.
1.3 Justification for the Study
The rationale of this study is scientific, environmental and economic in perspective. Given the scientific aspect, the isolation and characterization of native microalgae and bacteria in Edo State aquaculture ponds will yield new knowledge on the biodiversity of freshwater microbial producers of productive ecological groups in the state and their functional property concerning wastewater treatment. Ecologically, the technical rationale behind large scale reduction of nutrient loads on the receiving water bodies by aquaculture activities will be validated with an effective, indigenous-organism-based effluent treatment method, which will enhance the ecological health of the river systems in Edo State. Microalgae-bacteria consortium treatment systems are economically simple and low in capital costs, so they are feasible when used by smallholder fish farmers, which are the majority of the aquaculture industry in the state, and biomass valorization provides additional might of revenue-generating to what otherwise would be a remedial-oriented business (Hernandez-Garcia et al., 2021; Sutherland & Craggs, 2021).
1.4 Aim and Objectives of the Study
The aim of this study is to isolate, characterize, and evaluate indigenous microalgae and bacterial consortia from local ponds in Edo State for the bioremediation of fish pond effluent.
The specific objectives are to:
- Characterize the physicochemical and microbiological properties of fish pond effluent samples collected from selected aquaculture facilities in Edo State.
- Isolate and identify indigenous microalgae from local ponds using morphological and molecular (rbcL, 18S rRNA) characterization methods.
iii. Isolate and characterize indigenous effluent-degrading bacterial consortia from local ponds using biochemical tests and 16S rRNA gene sequencing.
- Evaluate the nutrient removal efficiency (nitrogen, phosphorus, biochemical oxygen demand) of selected microalgae–bacteria consortia in batch bioremediation experiments using authentic fish pond effluent.
- Assess the biomass productivity of microalgae during effluent treatment and evaluate the potential valorization of harvested biomass as aquaculture feed supplement.
1.5 Research Hypotheses
H₀₁: Indigenous microalgae isolated from Edo State ponds do not significantly reduce nitrogen and phosphorus concentrations in fish pond effluent.
H₀₂: There is no significant difference in biochemical oxygen demand removal between treatments employing microalgae alone, bacterial consortia alone, and combined microalgae–bacteria consortia.
H₀₃: Indigenous microbial consortia from local ponds do not produce significantly better effluent treatment performance than reference commercial strains.
1.6 Scope of the Study
The study will focus on fish pond effluent from catfish and tilapia farms in selected local government areas in Edo State. Indigenous microalgae and bacteria will be isolated from ponds within the study area. Bioremediation experiments will be conducted under controlled laboratory conditions using batch photobioreactor systems. The assessment will focus on key water quality parameters including biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen, ammonium-nitrogen, total phosphorus, and total suspended solids. Biomass valorization assessment will be limited to nutritional proximate analysis of harvested algal biomass.
1.7 Significance of the Study
This study will produce the first systematic characterization of indigenous microalgae and effluent-degrading bacterial communities in Edo State aquaculture pond systems and the first empirical evaluation of their combined performance in fish pond effluent bioremediation. The findings will provide fish farmers, extension officers, and state regulatory agencies with practical, evidence-based guidance on low-cost biological effluent treatment approaches suited to the scale and resource constraints of Edo State aquaculture. The research will additionally contribute to the global database on tropical aquaculture wastewater treatment and establish a local germplasm of indigenous microalgal strains with confirmed treatment performance that can be disseminated to farming communities through extension programmes.
1.8 Definition of Terms
Fish Pond Effluent: Wastewater generated from aquaculture operations through pond drainage, water exchange, harvest, and the continuous accumulation of uneaten feed, fecal matter, and metabolic excretions, typically characterized by elevated biochemical oxygen demand, ammonium, phosphate, and suspended solids (Eze et al., 2021).
Microalgae: Microscopic photosynthetic microorganisms including Chlorophyta, Cyanobacteria, Bacillariophyta, and other algal divisions that inhabit aquatic environments and assimilate inorganic nutrients through photosynthesis, growing as single cells, colonies, or filaments (Hernandez-Garcia et al., 2021).
Bacterial Consortia: A defined or undefined assemblage of multiple bacterial species acting cooperatively in the transformation, degradation, or immobilization of substrates or pollutants, often with complementary metabolic capabilities that collectively achieve outcomes not attainable by individual species (Srivastava et al., 2022).
Eutrophication: The process by which excessive nutrient inputs, particularly nitrogen and phosphorus, stimulate the excessive growth of algae and aquatic plants in water bodies, leading to oxygen depletion, disruption of biodiversity, and degradation of water quality (Ugwuanyi & Ugwuanyi, 2020).
Biochemical Oxygen Demand (BOD): A measure of the amount of dissolved oxygen consumed by biological processes during the decomposition of organic matter in a water sample over a specified period (typically 5 days at 20°C), used as a surrogate indicator of the organic pollution load of wastewater (Foladori et al., 2020).
Bioremediation: The use of living organisms or their products to degrade, transform, or remove environmental contaminants, restoring a polluted system to a less contaminated or non-toxic state (Abioye et al., 2021).
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