EFFECTS OF WASTEWATER IRRIGATION ON NUTRIENT ACCUMULATION ON SELECTED PLANTS IN JUJA

Transcription

1 Murage and Mwangi al 17 EFFECTS OF WASTEWATER IRRIGATION ON NUTRIENT ACCUMULATION ON SELECTED PLANTS IN JUJA Murage H* and Mwangi J Horticulture Department, Jomo Kenyatta University of Agriculture and Technology, P.O Box , Nairobi, Kenya *Correspondence: hunjamurage@gmail.com Abstract Rapid increase in urbanization and industrialization as well as large scale commercial farming has a wastewater management challenge to urban communities. In Kenya, wastewater is a non utilized resource rich in minerals and is available all year round. Local authorities in Kenya lack the capacity to safely dispose of wastewater and communities living along wastewater drains use the water for irrigating vegetables resulting in heavy metal poisoning, as well as infestation by coliform bacteria. The cost of proper wastewater treatment is prohibitive for most developing countries like Kenya. Wastewater reuse provides a means for income generation and provides a safe means for disposing the pollutant, and thus it needs to be recognized as a resource and not seen simply as waste. Hybrid poplars are trees that grow that are well suited to use agricultural, industrial, and community wastewater. Poplars are being used in the US as an alternative to expensive wastewater treatment systems, and methods which apply wastewater to annual crops or pasture. The trees serve a dual purpose as a nutrient sink for wastewater use and as a means to produce a short-rotation harvested wood product which helps offset the cost of installation and maintenance. The objective of this research was to evaluate nutrient accumulation efficiency of six plant species treated with domestic wastewater. A study was conducted in JKUAT, Juja, Kenya, from October 2009 to August 2011 to find out the efficiency of six plant species viz Casuarina equisetifolia, Cupressus lusitanica, Eucalyptus saligna, Grevillea robusta, Pennisetum perpureum and Pinus pitula nutrient accumulation from wastewater irrigation. Irrigation using clean water was used as control. A split plot design was used where wastewater and clean water were the main plot factors while the tree species were the subplot factors. After ten months of treatment leaf samples were collected for nutrient analysis. The percentage macronutrient (N, P, K, Mg and Ca) concentration and micronutrients levels of (Cu, Fe, Zn & Mn) in mg kg -1 were measured from the dry leaves of the plants. Irrigation with wastewater significantly increased the level of K and Mg in C. equisetifolia and G. robusta, Ca in E. saligna, N and Mg in P. perpureum and also N and K in P. patula. The level of Cu was significantly higher in all the six plant species after irrigation with wastewater compared to those irrigated with clean water. The accumulation of nutrients especially heavy metals like Mn, Zn, Cu resulting from short-term application of wastewater in comparison with clean water clearly indicates the potential role these plants can have in recycling of wastewater from residential areas where wastewater treatment systems are out of reach and are expensive to set up. Key words: Micronutrients, Macronutrients, Irrigation, Wastewater Introduction The rapid population growth in many municipalities in the world has placed increased demands on limited fresh water supplies. Many cities and districts are struggling to balance water use among municipal, industrial, agricultural, and recreational users. The population increase has not only increased the

2 18 Effects of Wastewater Irrigation on Nutrient Accumulation on Selected Plants in Juja fresh water demand but also increased the volume of wastewater generated. Municipalities, farmers, irrigation and agriculture departments are ill-equipped for the very sharp rise in urban-rural water transfers (Buechler and Scott, 2006). Use of wastewater for irrigating landscapes is often viewed as one of the approaches to maximize the existing water resources and stretch current urban water supplies (USEPA, 1992). Wastewater, often untreated, is used to irrigate 10% of the world s crops, according to the first ever global survey of wastewater irrigation (Dougherty et al., 2006). This is a largely hidden practice and is outlawed in many countries. However, many poor farmers, especially those in urban areas, use wastewater because it is free and abundant, even during droughts, and, being full of nitrates and phosphates, acts as an effective fertilizer (Dougherty et al., 2006). The use of wastewater by farmers cannot be ignored or dealt with by imposing bans on its use. Municipal policy-makers and planners need to confront the reality and face the challenge in innovative ways (Scott et al., 2004). Hybrid poplars are rapidly growing trees that are well suited to use agricultural, industrial, and community wastewater. They are being used in the US as an alternative to expensive wastewater treatment systems, and methods which apply wastewater to annual crops or pasture. The trees serve a dual purpose as a nutrient sink for wastewater use and as a means to produce a short-rotation harvested wood product which helps offset the cost of installation and maintenance (AF note - 17, 2000). In Kenya, wastewater is a non utilized resource rich in minerals and is available all year round. Wastewater is generated wherever there is human settlement, and is a potential health and pollution hazard if not properly disposed of or treated. Local authorities in Kenya lack the capacity to safely dispose of wastewater and communities living along wastewater pipes and trenches (Mwangi et al., 2006) use the water for irrigating vegetables resulting in heavy metal poisoning, as well as infestation by coli form bacteria. The cost of treating wastewater is prohibitive for most developing countries like Kenya. Wastewater reuse not only provides a means for income generation, but also provides a safe means for disposing the pollutant, thus it should be recognized as a resource and not seen simply as waste. Irrigation is an excellent use for wastewater effluent because of its nutritional content. The water provides dissolved nitrogen and phosphate nutrients; indeed some prefer wastewater to 'clean' water, and farmers using wastewater in Pakistan earn approximately US$300 more than those using normal irrigation water. Twenty five per cent of Pakistan's vegetables, including salads, are irrigated with wastewater (Scott et al., 1996). For small flows, the effluent can be used on special, well-supervised wastewater farms, where forage, fibre, or seed crops are grown and can be irrigated with standard primary or secondary effluent. However, agronomic aspects related to crops and soils must also be taken into account (Bouwer and Idelovitch, 1987). The deliberate reclamation of wastewater for potential reuse is therefore one of the keys to optimum utilization of water resources. Such reclamation for reuse will receive increased attention in the future as we endeavour to improve our environment and maintain equilibrium with nature (Sopper, 2003). The main objective of this research was to evaluate nutrient accumulation efficiency of six plant species treated with domestic wastewater. Materials and methods Site The experiment was conducted in Jomo Kenyatta University of Agriculture and Technology (JKUAT) located in Juja coordinates 1 o S 37 o E from April 2009 to August One trial was conducted in

3 Murage and Mwangi al 19 the green house while the other was conducted in the open field. Experimental design and treatment Both trials, green house and open field, were conducted using a randomized split plot experimental design. The water treatments, clean water and wastewater, were used as the main plots and the six different plant species as the sub plot factors. Six species of fast growing plant species of commercial importance in Kenya were sourced from Kenya Forest Services (KFS) in Thika. They were: Pinus patula, Casuarina equisetifolia, Eucalyptus saligna, Grevillea robusta, Cupresuss lusitanica, and Pennisetum purpureum. For the green house trial, farmyard manure, soil and sand were first sieved through a media sieve to obtain a relatively uniform media band which was mixed in a volumetric ratio of 1:2:3. The media was placed in planting pots of 20 cm diameter. The pots were arranged in the plots in a spacing of 0.5m x 0.5m. Each subplot carried ten plants. Planting was done in October, Transplanting was done in such a way as to ensure minimum disturbance to the root structure of the plants. Ten plants of each plant species were planted into the subplots in a RCBD with three replications of each within the main plots. Treatments involved clean water and wastewater application of 400mls of assigned water to every plant with the exception of P. purpureum which was watered using 1 liter of water due to high transpiration associated with the rapid growth of P. purpureum. The treatments were initially analyzed for nutrient content before starting the applications. Both treatments were applied 6 times a week. The plant tissues used to determine the content of micro and macro nutrients were the plant leaves about a week old from ten month old plants for each treatment. Seedlings of each variety were also sampled to act as the baseline data. The tissues were first air dried and then digested in a mixture of sulphuric acid, salicylic acid, hydrogen peroxide and selenium powder using an Aluminum block digester. Percentage Nitrogen (N) content was determined using Markham nitrogen still apparatus method. Percentage phosphorous (P) was determined using the colorimetric procedure for measuring total P without ph adjustment using Ascorbic Acid. Determination of percentage potassium (K), calcium (Ca) and magnesium (Mg) content of the plant tissue was measured by the complete oxidation of sample using Kjeldahl procedure followed by spectrometric analysis. The micronutrients levels of manganese (Mn), copper (Cu), zinc (Zn) and iron (Fe) were determined using an atomic absorption spectrometer. Data analysis All data was analyzed using Genstat. Mean separation was done by least significant difference (LSD 0.05 ) and values differing by more than the L.S.D value were considered significantly different. Results Nutrients levels analysis in wastewater and clean water used as treatments Nutrient analysis of wastewater and clean water indicated that wastewater has significantly higher nutrient concentrations of N, P, Ca, Mg, Fe, Zn and Mn, but a significantly lower concentration of Zn (Table 1). Concentration of nutrient in plants treated with clean water When the concentration of nutrient in the different species was compared after irrigation with clean water, G. robusta was found to have significantly the highest concentration of nitrogen followed by C. equisetifolia and C. lusitanica while P. patula and P. perpureum had significantly the lowest concentrations(table 2). The concentration of phosphorous was not significantly different across all the six plant species. C. lusitanica had the highest concentration of potassium (p < 0.001) while G.

4 20 Effects of Wastewater Irrigation on Nutrient Accumulation on Selected Plants in Juja robusta had the lowest (p < 0.001). For calcium, C. equisetifolia had the highest concentration (p < 0.001) followed by P.patula and E. saligna while G. robusta and P. perpureum had the lowest concentrations (p < 0.001). P. patula had the highest level of magnesium (p < 0.001) while G. robusta and P. perpureum had the lowest concentrations (p < 0.001). The level of Fe was high (p < 0.001) in C. equisetifolia while the concentrations of Zn were not significantly different across all the plant species. P. perpureum had the highest (p < 0.001) concentration of Mn while P. patula had the highest (p < 0.001) level of Cu. Concentration of Nutrient in plants treated with wastewater The concentration of different elements differed significantly across the six plant species treated with wastewater. G. robusta and P. perpureum had the highest (p < 0.001) concentrations of N, C. equisetifolia the highest concentration of K and E. saligna the highest concentration of Ca (Table 3). C. lusitanica had the lowest (p < 0.001) level of Mg while there was no significant difference in the level of P across all the six species. E. saligna and G. robusta had the highest (p < 0.001) level of Mg while C. lusitanica had the lowest (p < 0.001) level. There was no significant difference in the level of Fe across all the six plant species after wastewater treatment. However, E. saligna had high levels of Zn and Cu (p < 0.001), while P. patula had the highest level of Mn (p < 0.001). In C. lusitanica, wastewater treatment reduced the concentration of N, K, Ca and Mg to 1.1 %, 0.6 %, 0.27 % and 0.26 %, respectively compared to the clean water treated plants (p < 0.001). The concentrations of Ca and Mg in E. saligna increased in wastewater treated plants (p < 0.001). The concentration of N and P were equal in both treatments. In G. robusta nutrient accumulations for P, K and Mg were higher (p < 0.001) in wastewater treated plants while for N the level was higher but non-significant. The level of Ca was lower (p < 0.001) in wastewater treated plants in G. robusta. In P. purpureum the % concentration of N, P, Ca, and Mg were higher (p < 0.001) in wastewater treated plants while the % concentration of K was equal in both treatments. In P. patula, the % concentration of N, P and K was higher (p < 0.001) in wastewater treated plants compared to the clean water treated plants while the concentrations of Mg and Ca were not significantly different. Comparison of micronutrients levels (%) in wastewater and clean water treated plants In C. equisetifolia accumulation of Cu increased (p < 0.001) to mg kg -1 for plants treated with wastewater while for Fe, Zn, and Mn the level were lower (p < 0.001) at 86.4, 66.4 and 78.7 mg kg -1 respectively, in wastewater treated plants when compared to clean water treated plants (Table 5). Macronutrients levels (%) analysis in wastewater and clean water treated plants Changes in plant nutrient status in C. equisetifolia indicated that wastewater irrigation had altered the internal nutrient balance. Wastewater irrigation reduced concentration of N and Ca and increased the concentration of K. Concentration of K and Mg was higher (p < 0.001) in wastewater irrigated plants (Table 4).

5 Murage and Mwangi 21 Table 1: Nutrient concentration of clean water and wastewater used in the experiment % Mg kg -1 Element N K P Mg Ca Mn Fe Zn Cu WW CW CW = Clean water, WW = wastewater Table 2: Nutrient concentration of plants treated with clean water Macro elements Tree species Treatment % N % P % K % Ca % Mg Fe (mg kg -1 ) Zn (mg kg -1 ) Micro elements Mn (mg kg -1 ) P. patula CW C. equisetifolia CW C. lusitanica CW E. saligna CW G. robusta CW P. perpureum CW Mean Av. LSD CW= Clean water Cu (mg kg -1 ) Table 3: Nutrient concentration of plants treated with wastewater Macro elements Micro elements Fe Zn Mn Cu Tree sp Treatment % N % P % K % Ca % Mg (mg kg -1 ) (mg kg -1 ) (mg kg -1 ) (mg kg -1 ) C. equisetifolia WW C. lusitanica WW E. saligna WW G. robusta WW P.perpureum WW P.patula WW Mean Av. LSD WW = wastewater

6 22 Effects of Wastewater Irrigation on Nutrient Accumulation on Selected Plants in Juja Table 4: Comparison of macro elements nutrient accumulation between clean water and wastewater treated plants Macro-Elements Tree species Treatment % N % P % K % Ca % Mg C. equisetifolia BL C. equisetifolia CW C. equisetifolia WW Mean C. lusitanica BL C. lusitanica CW C. lusitanica WW Mean E. saligna BL E. saligna CW E. saligna WW Mean G. robusta BL G. robusta CW G. robusta WW Mean P. perpureum BL P. perpureum CW P. perpureum WW Mean P. patula BL P. patula CW P. patula WW Mean BL = baseline, CW = Clean water, WW = wastewater

7 Murage and Mwangi al 23 Table 5: Comparison of Micronutrients levels of plants treated with clean water and wastewater Micro-Elements Tree sp Treatment Fe(mg kg -1 ) Zn(mg kg -1 ) Mn(mg kg -1 ) Cu(mg kg -1 ) C. equisetifolia BL C. equisetifolia CW C. equisetifolia WW Mean C. lusitanica BL C. lusitanica CW C. lusitanica WW Mean E. saligna BL E. saligna CW E. saligna WW Mean G. robusta BL G. robusta CW G. robusta WW Mean P. perpureum BL P.perpureum CW P. perpureum WW Mean P. patula BL P. patula CW P. patula WW Mean BL = Baseline, CW =Clean water, WW = Wastewater In C. lusitanica, the concentrations of Zn and Cu were higher (p < 0.001) in plants treated with wastewater compared to those treated with clean water; while the concentrations of Fe and Mn were lower (p < 0.001) in wastewater treated plants. In E. saligna nutrient concentrations of Cu and Zn increased (p < 0.001) in wastewater treated plants to and mg kg -1 respectively, compared to clean water treated plants at and 87 mg kg -1, but were lower

8 24 Effects of Wastewater Irrigation on Nutrient Accumulation on Selected Plants in Juja (p < 0.001) for Fe, Zn and Mn at 92, 107 and 103 mg kg -1 respectively. In G. robusta the plants treated with wastewater had lower (p < 0.001) Zn, and Mn levels at 77.3 and 48.4 mg kg -1 respectively, but higher (p < 0.001) Cu levels at mg kg -1 when compared to clean water treatment. The level of Fe was not significantly different in wastewater treated plants. In P. purpureum the content of Cu was higher (p < 0.001) in wastewater treated plants at mg kg -1 while the levels of Fe, Zn and Mn at 74.4, 98.8, and 85.2 mg kg -1 respectively were lower (p < 0.001) in wastewater treated plants compared to plants treated with clean water. In P. patula the level of Mn and Cu increased (p < 0.001) to and mg kg -1 respectively for wastewater treated plants while for Fe and Zn the levels were lower (p < 0.001) at 70.5 and 64.7 mg kg -1 respectively. Discussion and Conclusion According to Farooq et al. (2006) wastewater individually increases the concentration of N, P and K in plants as compared to tap water. This was observed in G. robusta and P. purpureum. In the other four species, there was a decrease in the concentration of the three elements. These results support the findings of Mirghan et al. (2002) who compared the potential of normal and sewage water on plants belonging to family Poaceae. In contrast, Bozkurt and Yarilga (2003) found no significant increase in P, K, Ca, Ni, Cr and Cd concentrations in leaf samples of apple trees with sewage sludge applications. The decrease in the levels of N, P and K due to wastewater treatment conforms to observation made by Farooq et al. (2010) who found that water types and salinity levels significantly affected the nitrogen, phosphorus and potassium concentration in plant material. Salinity is a complex environmental constraint that presents two main components: an osmotic component due to the decrease in the external osmotic potential of the soil solution and an ionic component linked to the accumulation of ions that become toxic at high concentrations (mainly Na +, Cl -, SO 4 2+, CO 3 2- & HCO 3 -) and a stressinduced decrease in the content of essential ions, such as K + and Ca 2+. The effect of salinity on the nutrient composition of plant tissues, especially concentrations of K+ and Ca2+, has been extensively investigated and several researchers have proposed that the detrimental effects of salinity on plant growth may occur through an ionic imbalance, particularly of K + and Ca 2+ (Cerda et al., 1995). Plant species differ in their sensitivity or tolerance to salts (Ramoliya & Pandey, 2006; Masilamani et al., 2009, Tewari et al., 2006). Wastewater increases Na concentration which in turn reduces the uptake of the other elements. Stewart et al. (1990) observed that accumulation of nutrients differed significantly between species. From the results irrigation with wastewater gave the highest concentrations of N in P. purpureum, of P in P. patula, of K in C. equesetifolia and P. patula. The concentrations of Ca and Mg were higher in E. saligna and G. robusta. The concentrations for Fe, Zn and Mn were higher in plants irrigated with clean water apart from in P. patula for Zn and Mn which were higher in wastewater irrigated plants. Apart from G. robusta all the plant species irrigated with wastewater showed an increase in concentration of Cu being highest in E. saligna, followed by P. perpureum and C. lusitanica. This indicates the importance of these plants in the removal of heavy metals from wastewater. The accumulation of the heavy metals by the plants is important in reducing their concentrations in effluents released into the water bodies thus lowering pollution. However, high accumulation of the heavy metals in P. purpurea raises the concern on the use of wastewater in irrigating it for urban daily farming. This would cause their accumulation in the food chain thus becoming a health hazard. In conclusion, all the tested plant species can be useful in the removal of Cu from wastewater. E. saligna also has the ability to remove Zn while P. patula can be useful for removal of Mn from wastewater. These points to their potential use as alternatives to wastewater treatment systems

9 Murage and Mwangi al 25 which are expensive to set up and out of reach of most upcoming residential estates. Acknowledgement Appreciation goes to the National Council for Science and Technology (NCST) for providing financial support to this project and Jomo Kenyatta University (JKUAT) for providing the space and physical facilities to carry out the research. References AF Note 17., Agro forestry Notes, Special Applications -3, USDA Forest Service. USDA Natural Resources Conservation Service, pp4. Bouwer H., and Idelovitch E., Quality requirements for irrigation with sewage water. Journal of irrigation and drainage engineering 113(4): Bozkurt, M.A and Yarilga T., The Effects of sewage sludge applications on the yield, growth, nutrition and heavy metal accumulation in apple trees growing in dry conditions. Turkish Journal of Agriculture 27: Buechler, S. and Scott C., Wastewater as a Controversial, Contaminated, Yet Coveted Resource in South Asia. Human Development Report 2006.United Nations Development Program. New York. Cerda A., Pardines J., Botella M.A and Martinez V., Osmotic sensitivity in relation to salt sensitivity in germination of barley seeds. Plant Cell Environment 9: Dougherty, M., Dymond, R.L., Grizzard T.J. Jr, Godrej, A.N., Zipper, C.E., Randolph, J., 2006 Quantifying long-term NPS pollutant flux in an urbanizing watershed. J. Environ. Eng. 132: Farooq H., Siddiqui M.T., Farooq M., Qadir E. and Hussain Z., Growth, nutrient homeostasis and heavy metal accumulation in Azadirachta indica and Dalber giasisso Seedlings Raised from Wastewater. International Journal of Agriculture and Biology 8: Farooq, H., Batool N., Iqbal J. and Nouman W., Effect of salinity and municipal wastewater on growth performance and nutrient composition of Acacia nilotica L. International Journal of Agriculture and Biology 12: Masilamani, P., Saravanapandiyan P. and Annadurai K., Effect of Soil Alkalinity and Organic Matter on Germination and Growth of Eucalyptus tereticornis. Madras Agricultural Journal, 96: Mirghan, T.I., B.H. Nada and M.N. Malik., Utilization of Treated Sewage Water for Forage Production. Environment and Natural Resources Research Institute- National Center for Research, Khartoum, Sudan Mwangi, S; Kimathi, M; Kamore, M; Karanja, N and Njenga, M., Creating Viable Markets Opportunities for Poor Women Farmers in Kenya, RUAF.VOL.17 Rahmani, H.R., Use of industrial and municipal effluent water in Esfahan province- Iran. Scientific Research Essay 2: Ramoliya, P.J. and Pandey A.N., 2006.Effect of salinization of soil on emergence, growth and survival of Albizzia lebbek seedlings. Tropical Ecology 47: Scott C, Faruqui N.I, Raschid L., Wastewater use in irrigated agriculture: Managemnet, challenges in developing countries. In: Scott C, Faruqui NI, Raschid L, (eds.), Wastewater use in irrigated agriculture: confronting the livelihood and environmental realities. CABI Publishing, Wallingford; IWMI, Colombo; IDRC, Ottawa, pp Singh, G., Bhati, M., Growth, Biomass Production and Nutrient Composition of Eucalyptus seedlings irrigated with Municipal Effluents in a Loamy Sand Soil of Indian Desert. Journal of Plant Nutrition 26(12): Sopper, E.W, Disposal of municipal wastewater through forest irrigation. Environmental Pollution (1970) 1(4):

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