CHAPTER ONE
INTRODUCTION
Background of Study
Wastewater has been a major source of contamination since the beginning of the industrial age. Globally, two million tons of sewage, industrial and agricultural toxic waste is discharged into the world’s waterways and at least 1.8 million children under five years die every year, or one in every 20 seconds from water related
diseases (UNEP, 2010). An estimated 90 percent of wastewater in developing countries is discharged untreated directly into oceans, rivers and lakes (UN-GLAAS, 2008).
Africa’s quest to industrialize and increase food production implies production of more contaminated waters from industries, agricultural fields and domestic sources. Inadequate infrastructure and management systems for the increasing volume of wastewater will be at the heart of the wastewater crisis (UNU-INRA, 2013). This will continue to provide the greatest health challenges restricting development and increasing poverty through costs to health care, lost labour and productivity (Corcoran, Nellemann, Baker, Bos, Osborn and Savelli, 2010). Worldwide, almost 900 million people still do not have access to safe water and some 2.6 billion, almost half the population of the developing world do not have access to adequate sanitation (UNEP, 2010). Wastewater is increasingly becoming an important resource in Africa and other developing countries of the world. As more countries particularly in Africa enter the water stress (less than 1,700 m3 per capita yr-1) and scarcity class, demand for wastewater for irrigation and other purposes is likely to escalate (Oku and Asubonteng, 2013).
Statement of the Problem
Wastewater abounds in every municipality particularly in large cities were they are domestic, industrial and agricultural wastes. These wastes are disposed without serious concern on their pollution effect on surface and ground water quality. Wastewater contaminants are mostly suspended solids, phosphates, nitrates and heavy metals. Conventional methods (such as precipitation) used in treating polluted water are not only expensive beyond the reach of many developing countries, but do not provide sustainable solutions, as the contaminants are merely transferred from the wastewater to a sludge residue which end up in landfills (Ajayi and Ogunbayo, 2012). These contaminants eventually find their way into fresh water bodies resulting in various levels of pollution such as; eutrophication, water-borne diseases (such as cholera), accumulation of heavy metals in aquatic animals which serve as food to man and subsequently affecting man. To avert the cost implication and health impact of advanced treatment of wastewater, an eco-friendly, cheap and sustainable approach through phytoremediation became imperative.
1.3 Justification
Phytoremediation which involves the use of plants to solve environmental problems has been used for the treatment of different types of wastewater by several researchers in many countries including Australia, India, China, Haiti and Vietnam (Truong and Hart 2001).
Vetiver grass (Chrysopogon spp) is an herbaceous perennial plant with erect and stiff leaves of about 0.5 - 1.5 meter in length. It has a high affinity for both organic and inorganic chemicals, thus making it suitable for a cost effective, aesthetic, and an environment friendly approach for remediation of waste water from different sources. Various contaminants have been minimized in India, China, Australia and Venezuela using Vetiver grass. These contaminants include nitrogen, phosphorus, conductivity, hardness and suspended solids, etc (Roongtanakiat and Chairoj, 2001; Truong, Tran and Pinners, 2008).
Three species of Vetiver grass are known. They are Chrysopogon zizanioides (L.) Roberty, native to India, Chrysopogon nigritanus (Benth) Veldkamp, native to Western and Southern Africa and Chrysopogon nemoralis (Balansa) Holttum, native to Vietnam (Truong et al., 2008). Comparative studies of C. zizanioides and C. nemoralis showed that different species of Vetiver have different potentials (Truong, 2000). The potentials of C. zizanioides have been established in Asia. Although soil conservation trials with C. zizanioides have been reported in Nigeria (Babalola, Jimba, Maduakolam and Dada, 2003; Nzeribe and Nwachukwu, 2008), the use of Vetiver in Africa is still in its infancy. The potential of Africa’s indigenous species (C. nigritanus) in wastewater cleaning (that is one of Africa’s critical challenges) is not well known or documented (UNU-INRA, 2013) and its biosystematics is completely lacking.
1.4 Scope and Limitations
This research seeks to assess the use of Vetiver in the clean-up of major wastewater sources in Abakaliki. It entails a detailed systematic study and comparison of two species of Chrysopogon. The morphology, anatomy and field performances of both species were evaluated to know their basic differences which may suggest their potentials in phytoremediation. This study also highlights the economic potential of Vetiver and encourages the planting of Vetiver plants for other uses such as handicrafts, perfumes, aesthetics, erosion control and medicinal usage.
However, this work does not entail microbial study of the root zone of Vetiver in relation to phytoremediation. The use of modern biotechnological tools in the analysis and cross-breeding of these plants are aspects that are not covered in this work, but hope to be addressed in subsequent works.
1.5 Aim and Objectives
Considering the limited studies on the potentials of the African Vetiver when compared with Asian species, it became imperative to carry out a detailed study of the biosystematics and physiological properties of this species. The main objective of the study was to evaluate the biosystematics of two species of Chrysopogon and their effectiveness in phytoremediation of wastewater.
The specific objectives of the study were to:
- Determine the field performance of C. nigritanus and C. zizanioides.
- Evaluate the effectiveness of C. nigritanus and C. zizanioides in the treatment of wastewater.
- Compare the anatomical features of the aforementioned species.
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