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European Journal of Applied Sciences – Vol. 12, No. 3

Publication Date: June 25, 2024

DOI:10.14738/aivp.123.17104.

Chimi, A. N., Lekeufack, M., Djumyom, G. V. W., Nguetsop, V. F., & Fonkou, T (2024). Treated Domestic Sewage as A Nutrient

Source for Tomatoes (Solanum lycopersicum) Growth and Yield in A Hydroponic System in Yaoundé – Cameroon. European

Journal of Applied Sciences, Vol - 12(3). 338-352.

Services for Science and Education – United Kingdom

Treated Domestic Sewage as A Nutrient Source for Tomatoes

(Solanum lycopersicum) Growth and Yield in A Hydroponic

System in Yaoundé – Cameroon

Adrienne Njomou Chimi

Research unit of Applied Botany, University of Dschang

Martin Lekeufack

Research unit of Applied Botany, University of Dschang

Guy Valerie Wafo Djumyom

Research unit of Applied Botany, University of Dschang

Victor François Nguetsop

Research unit of Applied Botany, University of Dschang

Theophile Fonkou

Research unit of Applied Botany, University of Dschang

ABSTRACT

The exploitation of marshy lowlands for agricultural purposes in African cities,

with a clear predominance of market gardening, calls for concern about the

availability of exploitation sites and the doubtful quality of the water used. This

situation, particularly in urban areas, prompts farmers to look for alternative

solutions, like hydroponics, a growing technique that does not only rationalizes

the use of space, but saves water and mineral fertilizers, and simplifies growing

techniques, but above all eliminates soil-related problems and increases yields.

The aim of this research is to use treated sewage in hydroponics for tomato

production in urban agriculture in the city of Yaoundé. The experiments were

conducted in a completely randomized bloc design system with three replications.

The effluents were obtained from the Messa domestic sewage treatment plant.

Five treatments including raw effluent (T1); 50% diluted effluent (T2); 75%

diluted effluent (T3); Maxigro 10-5-14 chemical fertilizer solution at a dose of 100

g per 50 l of tap water (positive control) (T4), and tap water (negative control)

(T5) were applied to the tomatoes. The growth parameters considered plant

height, leave number, and number of fruits. Lycopene, protein, phenol, and

flavonoid content were also evaluated. The results show that 75% diluted effluent

(T3) significantly (P<0.05) improved tomato growth, with values of 24±0.60 cm

for plant height, 24.16±0.074 for leave number, and 72±6 for number of fruits

compared with the negative control. However, the raw effluent (T1) and the 50%

diluted effluent (T2), significantly improved the organo-mineral quality of the

tomatoes (P<0.05) with 2.05±0.50 μg/g and 1.74±0.11 μg/g for lycopenes, 0.14

±0.04μg/100g and 0.21±0.011 μg/100g for proteins, 5.73±0.25 μg/100g and

6.32±0.35 μg/100g for phenols, and 21.41±3.09 μg/100g and 29.08 ±2.27μg/100g

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339

Chimi, A. N., Lekeufack, M., Djumyom, G. V. W., Nguetsop, V. F., & Fonkou, T (2024). Treated Domestic Sewage as A Nutrient Source for Tomatoes

(Solanum lycopersicum) Growth and Yield in A Hydroponic System in Yaoundé – Cameroon. European Journal of Applied Sciences, Vol - 12(3). 338-

352.

URL: http://dx.doi.org/10.14738/aivp.123.17104

for flavonoids respectively) compared to the negative control. The highest yield

was obtained with the positive control (T4), followed by treatment (T3); with

estimated fruit number of 34±3 and 27±2 fruits/m2 respectively. The reuse of

treated wastewater in hydroponics would be an innovative technique that would

alleviate the current problems of urban agriculture in the city of Yaoundé.

Keywords: Effluent, hydroponics, Solanum lycopersicum, urban agriculture.

INTRODUCTION

Between now and 2030, the world's population will increase by 3 billion people, with 95% in

developing countries. According to a UN, [1] report on urbanization, 60% of the population of

developing countries will be living in cities by 2030 [1]. To meet the food needs of this rapidly

growing population, agricultural production will have to double by 2030 and quintuple by

2050 [2]. At the same time, waste and effluent will quadruple in the cities [3]. These trends,

their potential impact, and the challenges of managing the impact will be particularly

pronounced in regions undergoing rapid urbanization, such as sub-Saharan Africa [3]. In

urban areas, large quantities of solid and liquid wastes are produced and drinking water is

becoming progressively scarcer, while more sewage continues to be generated [4]. In view of

the scarcity and the competition for water resources and the negative impact of untreated

sewage on human health and the environment, it is necessary to develop innovative

strategies for managing water pollution in urban areas, with emphasis on reclamation [5].

Urban agriculture plays a very important and significant role in the economic activities of the

population of many cities in sub-Saharan Africa [6]. Developed and booming in recent years,

urban agriculture appears to be an alternative way of combating poverty by adding value to

by-products of sewage treatment [7, 8]. The literature has highlighted the food, economic,

environmental, socio-spatial, and socio-political attributes of urban agriculture [9,10].

However, urban agriculture is faced with a number of constraints, including insecurity of land

tenure, reduction of agricultural areas, impact of different agricultural practices

(deforestation, water and/or soil pollution), environmental risks (soil erosion and flooding),

and the preservation of natural areas [11]. The shortage of arable land is leading to heavy use

of agrochemicals, which are potentially harmful to health and the environment [12].

The city of Yaoundé is not immune to this situation; it has experienced a demographic

explosion over the last three decades, with an exponential increase in its population

estimated at 3,555,257 [13]. The corollary of this, has been the densification of the urban

space, and the strong pressure exerted on natural resources, the colonization of marshy

lowlands for agricultural purposes, with a clear predominance of market gardening [14]. This

activity, which is widespread in the Yaoundé marshy lowlands, contributes to food security

and offers opportunities such as jobs creation, development of open spaces, economic

integration of the populations in difficulties, and environmental clean-up [14, 15, 16]. Despite

its many benefits, urban agriculture as practiced in Yaoundé exposes people and farmers to

numerous health risks, as the waters used are very often loaded with various germs,

including fecal coliforms (5025 CFU/100ml to 3 x 106 CFU/100ml), fecal Streptococci (1960

CFU/100ml to 138,000 CFU/100ml) and, above all, variable levels of protozoan cysts

(Entamoeba hystolitica and Giardia sp) and helminth eggs. The reuse of sewage therefore

leads to an upsurge in water-borne diseases such as intestinal amoebiasis, which affects both

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European Journal of Applied Sciences (EJAS) Vol. 12, Issue 3, June-2024

the people involved in the sector and the general population, regardless of gender, age or

social status [17, 14]. In addition to these risks, these waters also receive pesticide residues

from market gardeners. The use of such waters for irrigating vegetables is not without danger

[18]. Moreover, the space occupied by market gardeners is gradually being reduced in favor

of urban development. In view of the scarcity of arable land, the quality of the site, and the

water used in urban agriculture, and with a view to modernizing urban agriculture in the

context of sustainable development, the aim of this research work is to set up a functional

hydroponic system to assess the effect of treated wastewater on the growth and organo- mineral composition of tomatoes (Solanum licopersicum). Hydroponics can be used in densely

populated urban areas such as Yaoundé and Douala, where there is no suitable land for

cultivation, and in regions with hot weather or insufficient sunshine. In addition to these

advantages, hydroponics offers cost savings thanks to reduced labor, a more efficient

production system than conventional systems and year-round production [19].

MATERIAL AND METHODS

Study Site

The experiments were conducted at the Essos district, in the 5th sub-division of the city of

Yaoundé, Mfoundi Division, Central Region of Cameroon. The experimental setup is located at

latitude 3.8761863 N and longitude 11.5488447 E (UTM), and at 762 m of altitude. The

climate is tropical, with two alternating dry and rainy seasons: the long dry season runs from

mid-November to mid-March, the short rainy season from mid-March to mid-June, the short

dry season from mid-June to mid-August and the long rainy season from mid-August to mid- November. The city of Yaoundé extends over 310 km2 surface area with an urbanized surface

area of 183 km2. In 2020, it will be home to an estimated population of 4,100,000, with an

average density of 13,486 inhabitants per km2 and 775,911 lodgings in 2017. The city's

growth rate was almost 5.3% per year between 2001 and 2015 and 5.7% between 2015 and

2020 [20]. Of the 13 sewage treatment plants that existed between 1967 and 1990, almost all

are dysfunctional. However, since 2010, three of these plants have been restored (Grand

Messa, Cité Verte and Biyem-Assi). The effluent for the experiment was collected from the

outlet of the Grand Messa sewage treatment plant outlet where, the treated sewage is

discharged into the Mingoa river.

Experimental Set-Up

The hydroponic system used was a gravity system with water recirculation (Figure 1). The

culture surface was sloped (5%) to facilitate the flow of the nutritive solution by gravity,

improve oxygenation and reduce heating [21]. The system consisted of five 50-litre tanks

containing the nutritive solutions constituting the treatments applied. These consisted of T1:

raw effluent; T2: 50% diluted effluent; T3: 75% diluted effluent; T4: Maxigro 10-5-14

chemical fertilizer solution at a dose of 100 g per 50 l of tap water (positive control) and T5:

tap water (negative control). Each treatment consisted of 15 tomatoes plants spaced 30 cm

apart vertically and horizontally, with an experimental unit of 2.67 m2. Each reservoir, fitted

with a tap connected to a 3 cm diameter plastic pipe, was used to feed the young seedlings.

For each treatment, the feed tube was connected to a series of 5 thinner plastic tubes 0.5 cm

in diameter, arranged in parallel to distribute the nutritive solution evenly along the

polyethylene bags, which were aligned vertically with three bags per slat/line and 30 cm

apart. This thin pipe was perforated and inserted along the series of polyethylene bags so that