Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
American Journal of Microbiological Research
Biomedical Science and Engineering

We are pleased to announce that submissions are now being accepted for peer review for all the journals across all our subject areas in SciEP.

Please submit your manuscript via our online submission system:
http://www.sciepub.com/author/signin

To unsubscribe from our mailing list, please click on the following link: unsubscribe

I am looking forward to hearing from you.

Kind regards,

David Rain
Email:join@sciepub.com
Science and Education Publishing (http://www.sciepub.com)

Impact of Urban Livestock Production on Groundwater Quality in Kaduna Metropolis, Nigeria

Terrumun Kenneth Kwadzah, Oliver Terna Iorhemen*, Charles Amen Okuofu

Department of Agricultural and Environmental Engineering, University of Agriculture, Makurdi, Nigeria

Abstract: Groundwater is the main source of water for most city dwellers in Nigeria. In this study, the impacts of urban livestock production on groundwater quality in Kaduna metropolis were assessed through water quality monitoring. Groundwater samples were collected from wells located around 2 abattoirs (Tudunwada and Kawo abattoirs) and in 8 livestock-keeping households for a 6-month period (July- December). Physico-chemical analyses were conducted on the samples using standard methods. Results indicate that groundwater is negatively impacted in terms of 5-day biochemical oxygen demand, chemical oxygen demand, nitrate-nitrogen, total phosphorus and cadmium; and this impact is of great concern as the values for these parameters are well in excess of established limits. There is negative impact in terms of pH, electrical conductivity, total dissolved solids and zinc but this impact is not a concern as most of the values are within limits. However, no impact was observed on groundwater quality in terms of calcium as it showed no definite pattern of variation. Similarly, iron exhibited very low concentrations in the samples with a few exceptions in the months of July and August for the two abattoir sites. Lead was not detected in any of the samples throughout the study period. This study indicates that livestock keeping and processing activities have negative impact on groundwater quality in Kaduna metropolis. The groundwater pollution due to urban livestock production emanates from point sources and control measures can be easily applied.

Keywords: abattoir, groundwater quality, Kaduna metropolis, livestock-keeping households, urban livestock production, wells

Received July 12, 2015; Revised July 27, 2015; Accepted August 26, 2015

Citation: Terrumun Kenneth Kwadzah, Oliver Terna Iorhemen, Charles Amen Okuofu, Impact of Urban Livestock Production on Groundwater Quality in Kaduna Metropolis, Nigeria. American Journal of Water Resources, 3 (4). 109-117. January 2015. doi:10.12691/ajwr-3-4-2

1. Introduction

Urban livestock production refers to the rearing and processing of animals within municipalities (towns and cities). Examples of these animals and the products derived from them include: cattle for milk, beef and hide; goats for meat; sheep for mutton and hide; poultry for eggs and meat; and pigs for pork. In addition to providing meat and other animal-related products, urban livestock production is a source of additional income [1] for the poorly remunerated employed civil servants and traders [2] as well as retired urban dwellers. Other benefits include: employment generation for the unemployed, opportunities for organic waste recycling and uplifting of social status [3]. It also contributes to the food supply of urban households that cannot afford to purchase all their food needs. Urban livestock production further serves to balance out the animal protein demand in the city and the supply from the rural areas where there may be issues of declining production, inefficient marketing and distribution due to decaying or non-existent infrastructure especially in developing countries.

In the early part of the 20th century, many municipalities were against urban livestock production due to perceived public health risks of rearing domestic animals in close proximity to humans [4]. The concern arose from the side effects arising from urban livestock production like the pollution of soil and groundwater resulting from animal excreta and animal remains [5,6] if there is no proper management in place. Additionally, if the animals are not kept on an intensive system, there may be issues of animal waste littering which may be unsightly as well as pose health hazards since livestock are known reservoirs of several zoonotic pathogens [7]. Furthermore, the waste from abattoirs, where the animals are slaughtered, pose another risk due to its high biochemical oxygen demand (BOD), nutrients and pathogens content [8,9]. Other animal-products processing industries like dairies and tanneries also have polluting effluents with attendant human and environmental health impacts.

However, due to increasing urbanization, urban livestock production is correspondingly expanding in order to feed municipal populations as well as generate household income [10] as stated earlier. In particular, the increasing demand for eggs, meat and milk is a major driving force for the expansion of urban livestock production [11]. The animals are kept under intensive systems or semi-intensive system [12] giving room for environmental-friendly management system if proper planning is done. In Nigeria too, the rearing of domestic animals in urban centres is a common practice.

In Kaduna metropolis, households that keep animals do so using intensive, semi-intensive or free range systems. At the abattoirs, the rumen contents of the slaughtered animals are heaped outside the abattoir and later spread on the bank of river Kaduna. This allows the liquid portion to simultaneously infiltrate into the ground and evaporate into the atmosphere. The management of the abattoir wastewater is another issue of concern.

Public water supply in Kaduna metropolis, like in most Nigerian cities, is not steady. This leads residents to resort to the abstraction of groundwater through private boreholes and hand-dug wells to supplement the public water supply. Hence, the quality of the groundwater within the metropolis is very important.

In this study, the aim was to investigate the effects of urban livestock keeping and processing activities on the groundwater quality in Kaduna metropolis through water quality monitoring.

2. Materials and Methods

2.1. Description of the Study Area

The study was conducted in Kaduna metropolis, Kaduna State, Nigeria. Kaduna metropolis lies between latitudes 10°N and 11°N, and between longitudes 7°E and 8°E, and at an altitude of 645m above sea level [13]. Kaduna is characterized by two distinct seasons in the year: the dry season and the rainy season. The dry season runs from late October to March and is characterized by cold and dry conditions with the 'harmattan' wind that blow from north-east towards the south-west. The rainy season, which runs from April to early October, is characterised by warm and humid conditions with winds blowing from the south-west towards the north-east. The average monthly temperature for the city is between 26°C and 34°C [13].

River Kaduna passes through the middle of the metropolis. On the northern bank of the river, Tudunwada abattoir is located in Kaduna South local government area (LGA) while the Kawo abattoir is located in the Kawo area of Kaduna North LGA. The livestock-keeping households used in the study were randomly selected from Chikun, Kaduna South and Kaduna North LGAs. Figure 1 below presents a map of the study area.

Figure 1. Map of the Study Area

2.2. Reconnaissance Survey

A reconnaissance survey of the site was done to get information regarding the kinds of animals kept, the rearing system, existing waste management practices and sources of water. The survey revealed that rumen contents at the Tudunwada and Kawo abattoirs are heaped outside the abattoir and later spread on the bank of river Kaduna or directly discharged into the river. The wastewater emanating from abattoir activities in Tudunwada is conveyed to a natural channel called ‘Blood River’ that empties into river Kaduna. At Kawo, the abattoir wastewater is conveyed via an unlined channel into a sanitary line.

Similarly, at the livestock-keeping households (LKHs), manure is collected and heaped outside uncovered. A few farmers bag the manure and keep it under the shade for sale to crop farmers who use it for soil amendment. Unsold manure at livestock markets is disposed of at waste disposal sites used by the Kaduna State Sanitation Authority. The location of these LKHs, type of animal kept and method of animal waste management are shown in Appendix 1.

2.3. Sampling Points

Water samples were collected from existing wells as follows: two (2) wells at Tudunwada abattoir, two (2) wells at Kawo abattoir, and one (1) well from each of the eight (8) LKHs randomly selected from Chikun, Kaduna South and Kaduna North LGAs for the study. In addition, one well each was selected at least 100m away from the Tudunwada and Kawo abattoirs to serve as control. The same thing was done for the LKHs.

2.4. Water Sampling

Grab water samples were collected from the selected existing wells as stated above each month, from July to December, using the buckets and ropes in regular use at the wells. The water samples were collected in 1-litre plastic bottles and taken to the laboratory for analyses. The collection of samples was done for a period of six consecutive months to capture water quality trends in the rainy season months (July to September) and dry season months (October to December). All the samples collected were transported to the laboratory and analysed within 2 hours of collection.

2.5. Laboratory Analyses

The following physico-chemical tests were conducted on the collected samples in the laboratory: pH, electrical conductivity (EC), total dissolved solids (TDS), 5-day biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), nitrate-nitrogen, total phosphorus, calcium, iron, zinc, lead and cadmium.

The pH was analyzed in-situ using Henna pH meter while EC and TDS were analyzed in the laboratory using standard methods. Chemical analyses were conducted in the laboratory according to the Standard Methods for the Examination of Water and Wastewater [14]. All the instruments were calibrated and standardized before using them for analyses. The determination of heavy metals was carried out by atomic absorption spectrophotometer techniques (Perkin-Elmer model 3110 equipped with HG500 graphite furnace), in flame or flameless mode, depending on element.

3. Results and Discussion

For ease of understanding, the meanings of the abbreviations used in the tables are presented below.

TAW: Tudunwada Abattoir Wells

TACW: Tudunwada Abattoir Control Well

KAW: Kawo Abattoir Wells

KACW: Kawo Abattoir Control Well

LKH: Livestock-keeping Household

NLKH: Non-livestock Keeping Household

3.1. pH

The pH values of all the samples tested are presented in Table 1 below.

Table 1. Variation of pH within the Study Period

The pH of a water sample is particularly important if the water is to undergo some form of chemical treatment e.g. coagulation/flocculation, disinfection, etc. The average pH values for samples from the Tudunwada abattoir wells were in excess of the control well from September to December. Most of the pH values fall within the range recommended by both the World Health Organisation (WHO) and Nigerian Standards for Drinking Water Quality (NSDWQ) which is 6.5 - 8.5 [15,16]. This implies that although there is impact on groundwater in terms of pH, this impact is not of a concern.

3.2. Electrical Conductivity

The EC values of all the samples tested are presented in Table 2 below.

Table 2. Variation of Electrical Conductivity (µS/cm)

EC values for all samples were above their corresponding control values throughout the study period. Most of the values for the two abattoirs were in excess of the maximum value recommended for drinking water by NSDWQ - 1300 µS/cm [16]. For the livestock keeping households, all the average values were within the limits throughout the study period. This clearly indicates that livestock keeping and processing has affected the groundwater quality in terms of EC. For the LKHs, although there is impact on the groundwater quality, all the values are within established safe limits.

3.3. Total Dissolved Solids

TDS values of all the samples tested are presented in Table 3.

Table 3. Variation of Total Dissolved Solids (mg/L)

The NSDWQ maximum permitted value for TDS in drinking water is 500 mg/L [16]. WHO on the other hand, states that drinking water becomes greatly and progressively unpalatable at TDS concentrations above 1000 mg/L [15]. The abattoir wells had TDS values above the NSDWQ limit of 500 mg/L from July to October. This corresponds to the rainy season when the animal waste would have been dissolved by the water that infiltrated and percolated into the soil. The LKHs had TDS below the limits throughout the study period. However, the TDS values obtained for the abattoir wells and LKHs were all above their corresponding controls, indicating an impact of livestock keeping and processing on groundwater quality.

3.4. Biochemical Oxygen Demand

The results obtained for BOD₅ (mg/L) are presented in Table 4 below.

Table 4. Variation of 5-day Biochemical Oxygen Demand (mg/L)

Most of the BOD₅ values are above 20 mg/L, the discharge consent for treated wastewater [17]. However, this value is too high for drinking water. All the values obtained for the abattoir wells and LKHs were all above their corresponding controls, indicating an impact on groundwater quality, though very small.

3.5. Chemical Oxygen Demand

Table 5 below presents the results obtained for COD (mg/L) throughout the study period.

Table 5. Variation of Chemical Oxygen Demand (mg/L)

The COD values are higher in magnitude than their corresponding BOD₅ counterpart in section 3.4 above. This is because COD is a measure of wastes which are both biodegradable and non biodegradable, hence covering a broader spectrum [18]. COD showed a similar pattern of variation as BOD₅. As with BOD₅, all the values obtained for the abattoir wells and LKHs were all above their corresponding controls.

3.6. Nitrate - nitrogen

The results obtained for nitrate - nitrogen in mg/L are presented in Table 6 below.

Table 6. Nitrate-nitrogen Variation (mg/L)

In order to protect bottle-fed infants against methaemoglobinaemia (blue-baby syndrome), WHO recommends 50 mg/L limit as nitrate ion or 11 mg/L as nitrate-nitrogen [15]. The NSDWQ on the other hand, stipulates a maximum permitted nitrate concentration of 50 mg/L in drinking water [16]. The nitrate-N levels in the abattoir wells and LKHs samples were all above their corresponding controls, indicating that livestock rearing and processing has effects on the groundwater quality. The high levels of nitrate - nitrogen are attributable to the interaction between livestock wastes in the vicinity of the wells and well water occasioned by unhygienic anthropogenic activities at the sites. In addition, the nitrate-N in the faeces and urine of animals around the sites moves with the infiltrating water through the soil into wells [19].

3.7. Total Phosphorus

Table 7 below presents the results obtained for total phosphorus (mg/L) throughout the study period.

Table 7. Variation of Total Phosphorus (mg/L)

Phosphorus is very essential for animals. It is required for normal soft and skeletal tissue (e.g. bones and teeth) development [20]. Hence animal waste and other organic wastes have relatively high levels of phosphorus [21,22,23]. A significant portion of the total phosphorus in soil solution is present as dissolved organic phosphorus [24]. The dissolved organic phosphorus infiltrates and percolates with soil water. One of the undesirable effects of phosphorus' presence in water is depletion of dissolved oxygen. In surface waters, other negative effects may include: eutrophication and death of aquatic animals. Total phosphorus levels were very low for all the samples. These concentrations were however, equal or above their corresponding controls, pointing to the contribution of animal wastes to the relatively higher levels of in abattoir and LKH samples.

3.8. Calcium

The results obtained for calcium in mg/L are presented in Table 8 below.

Table 8. Variation of Calcium (mg/L)

The presence of calcium in water is not known to cause physiological effects to humans [25], hence both NSDWQ and WHO have no limit for it in drinking water. However, calcium and magnesium are responsible for water hardness which leads to more soap consumption during laundry. Calcium showed no definite pattern of variation. Some control values were more than the tested samples. This shows that livestock activities around the sites had no direct influence on the calcium concentration.

3.9. Iron

The results obtained for iron in mg/L are presented in Table 9 below.

Table 9. Variation of Calcium (mg/L)

Iron is an essential macro nutrient for the normal functioning of all living organisms, hence animal wastes would contain iron. Though iron is beneficial in human diet at low concentrations [26], elevated concentrations produce objectionable reddish-brown colour in the water due to the oxidation of ferrous iron to ferric iron. The concentrations of iron in the samples were generally low with a few exceptions in the months of July and August for the two abattoir sites. The reason for this high values in those months could be as a result of pieces of iron that may have come in contact with the water since the wells had no cover, or dust and other extraneous materials may have found their way into the wells. Generally, the concentration of iron in natural fresh waters ranges from 0.5 to 50 mg/L [15]. NSDWQ recommended limit in drinking water is 0.3 mg/L [16]. This is because iron concentrations above 0.3 mg/L cause staining of laundry and plumbing fixtures [15]. Most samples met this standard during the study period.

3.10. Zinc

The results obtained for zinc in mg/L are presented in Table 10 below.

Zinc is an essential trace element found in almost all food; hence its source is diet. Drinking-water become unacceptable to customers at zinc concentrations above 3 mg/L [15]. Based on this, NSDWQ set a maximum threshold of 3 mg/L in drinking water [16]. None of the samples exceeded this value during the period of the study. However, all the samples were above their respective controls indicating an impact of livestock activities on groundwater quality. This impact, however, is of no concern.

Table 10. Zinc Variation (mg/L)

3.11. Lead

Lead was not detected in any of the samples throughout the study period.

3.12. Cadmium

The results obtained for cadmium in mg/L are presented in Table 11 below.

Table 11. Variation of Cadmium (mg/L)

Cadmium is a major health concern because it is known to cause lung, prostate and renal cancers [27]. Another big concern is cadmium's long half-life and persistence in the environment and in tissues [28]. In view of this, the guideline value of 0.003 mg/L has been set in both NSDWQ and WHO guidelines for drinking-water [15,16]. Cadmium was not detected in any of the samples in July and August but appeared in most sites from September to December. When it appeared, the detected levels were all above the NSDWQ and WHO maximum allowable concentration in drinking water. In the control samples, it was detected only in December at the Tudunwada abattoir, in September at Kawo abattoir and LKHs. However, the concentrations of cadmium in all the controls, when it appeared, were above the threshold. Also, the concentrations of the heavy metal in all the samples from September to October were above their corresponding controls. This indicates an impact of livestock wastes on groundwater; although the fact that the concentration of cadmium in the control samples were also above the threshold indicates that the presence of cadmium in groundwater may have also been contributed by natural sources.

4. Conclusion

Urban livestock production, in addition to providing meat and animal-related products, serves as additional income for low income earners, traders and retirees. It however, poses some environmental pollution threats. This research assessed the impact of livestock keeping and processing activities on groundwater quality in Kaduna metropolis through water quality monitoring from July to December.

Findings indicate that urban livestock production has negatively impacted groundwater in terms of pH, EC, TDS, and zinc but this impact is not a concern as most of the values are within NSDWQ and WHO guideline values. In terms of BOD₅, COD, nitrate-N, total phosphorus and cadmium, the levels detected show negative impact on groundwater of great concern. Cadmium's presence (concentrations well above NSDWQ and WHO limits) is also attributable to natural sources. However, urban livestock production showed no effect on groundwater in terms of calcium, iron and lead.

This research has shown that groundwater pollution caused by livestock wastes emanates from point sources: abattoirs and livestock-keeping households. This implies control measures can be easily applied at the source. The water quality data and pollution source information obtained from this research will be useful in identifying water quality problem areas and planning of engineering interventions.

Acknowledgement

The authors wish to acknowledge the immense contributions of the technicians and technologists at the Public Health Engineering Laboratory, Department of Water Resources and Environmental Engineering, Ahmadu Bello University, Zaria - Nigeria.

Statement of Competing Interests

The authors have no competing interests.

List of Abbreviations

BOD: Biochemical Oxygen Demand

BOD₅: 5-day Biochemical Oxygen Demand

COD: Chemical Oxygen Demand

DO: Dissolved Oxygen

EC: Electrical Conductivity

KACW: Kawo Abattoir Control Well

KAW: Kawo Abattoir Wells

LGA: Local Government Area

LKH: Livestock Keeping Household

NLKH: Non-livestock Keeping Household

NSDWQ: Nigerian Standards for Drinking Water Quality

TACW: Tudunwada Abattoir Control Well

TAW: Tudunwada Abattoir Wells

TDS: Total Dissolved Solids

TSS: Total Suspended Solids

WHO: World Health Organisation

References

Appendix 1: Location of livestock keeping households, types animal reared, and existing method of animal waste management

[1]   | Lupindu, A.M., Ngowi, H.A., A., D., Olsen, J.E., and Msoffe, P.L.M., (2012). Current manure management practices and hygiene aspects of urban and peri-urban livestock farming in Tanzania. Livestock Research for Rural Development, 2012. 24(9).
[2]   | Muhammad, I.R., (2008). Livestock Ownership and Unconventional Feed Resources from Refuse Dumps in Urban Metropolis of Semi Arid Zone. Research Journal of Animal Sciences, 2008. 2(1): p. 12-16.
[3]   | Gillah, K.A., Kifaro, G.C., and Madsen, J., (2012). Urban and peri urban dairy farming in East Africa: A review on production levels, constraints and opportunities. Livestock Research for Rural Development, 2012. 24(11): p. 198.
[4]   | McClintock, N., Pallana, E., and Wooten, H., (2014). Urban livestock ownership, management, and regulation in the United States: An exploratory survey and research agenda. Land Use Policy, 2014. 38: p. 426-440.
[5]   | Thys, E., Oueadraogo, M., Speybroeck, N., and Geerts, S., (2005). Socio-economic determinants of urban household livestock keeping in semi-arid Western Africa. Journal of Arid Environments, 2005. 63(2): p. 475-496.
[6]   | Mouri, G. and Aisaki, N., (2015). Using land-use management policies to reduce the environmental impacts of livestock farming. Ecological Complexity, 2015. 22: p. 169-177.
[7]   | Heuvelink, A.E., Valkenburgh, S.M., Tilburg, J.J.H.C., Van Heerwaarden, C., Zwartkruis-Nahuis, J.T.M., and De Boer, E., (2007). Public farms: hygiene and zoonotic agents. Epidemiology & Infection, 2007. 135(07): p. 1174-1183.
[8]   | Keskes, S., Hmaied, F., Gannoun, H., Bouallagui, H., Godon, J.J., and Hamdi, M., (2012). Performance of a submerged membrane bioreactor for the aerobic treatment of abattoir wastewater. Bioresource Technology, 2012. 103(1): p. 28-34.
[9]   | Matsumura, E.M. and Mierzwa, J.C., (2008). Water conservation and reuse in poultry processing plant—A case study. Resources, Conservation and Recycling, 2008. 52(6): p. 835-842.
[10]   | Mlozi, M.S., (1997). Impacts of urban agriculture in Dar es Salaam, Tanzania. Environmentalist, 1997. 17(2): p. 115-124.
[11]   | Udo, H.M.J., Aklilu, H.A., Phong, L.T., Bosma, R.H., Budisatria, I.G.S., Patil, B.R., Samdup, T., and Bebe, B.O., (2011). Impact of intensification of different types of livestock production in smallholder crop-livestock systems. Livestock Science, 2011. 139(1-2): p. 22-29.

[12]  
Lupindu, A.M., Dalsgaard, A., Msoffe, P.L.M., Ngowi, H.A., Mtambo, M.M., and Olsen, J.E., (2015). Transmission of antibiotic-resistant Escherichia coli between cattle, humans and the environment in peri-urban livestock keeping communities in Morogoro, Tanzania. Preventive Veterinary Medicine, 2015. 118(4): p. 477-482.

[13]   | Bununu, Y.A., Ludin, A.N.M., and Hosni, N., (2015). City profile: Kaduna. Cities, 2015. 49: p. 53-65.
[14]   | APHA, (1998). Standard methods for the examination of water and wastewater, 20th edition. Washington: American Public Health Association (APHA).
[15]   | WHO, (2011). Guidelines for Drinking-water Quality, 4th ed. Geneva: World Health Organization.
[16]   | NSDWQ, (2007). Nigerian Standard for Drinking Water Quality. Nigerian Industrial Standard NIS 554. Lagos, Nigeria: Standard Organization of Nigeria.
[17]   | Tebbutt, T.H.Y., (1998).Principles of water quality control. Boston, MA: ButterWorth-Heinemann.
[18]   | Han, D., Concise Environmental Engineering 1st edn. 2011.
[19]   | Hubbard, R.K., Newton, G.L., and Hill, G.M., (2004). Water quality and the grazing animal. Journal of Animal Science, 2004. 82(13_suppl): p. E255-E263.
[20]   | Esser, N.M., Hoffman, P.C., Coblentz, W.K., Orth, M.W., and Weigel, K.A., (2009). The effect of dietary phosphorus on bone development in dairy heifers. Journal of Dairy Science, 2009. 92(4): p. 1741-1749.
[21]   | Schumann, A. and Sumner, M., (2004). Formulation of Environmentally Sound Waste Mixtures for Land Application. Water, Air, and Soil Pollution, 2004. 152(1-4): p. 195-217.
[22]   | Wang, F., Sims, J.T., Ma, L., Ma, W., Dou, Z., and Zhang, F., (2011). The Phosphorus Footprint of China's Food Chain: Implications for Food Security, Natural Resource Management, and Environmental Quality. Journal of Environmental Quality, 2011. 40(4): p. 1081-1089.
[23]   | Li, G., Li, H., Leffelaar, P.A., Shen, J., and Zhang, F., (2014). Characterization of phosphorus in animal manures collected from three (dairy, swine, and broiler) farms in China. PLoS ONE, 2014. 9(7): p. e102698.
[24]   | Chardon, W.J., Oenema, O., del Castilho, P., Vriesema, R., Japenga, J., and Blaauw, D., (1997). Organic Phosphorus in Solutions and Leachates from Soils Treated with Animal Slurries. Journal of Environmental Quality, 1997. 26(2): p. 372-378.
[25]   | Alley, E.R., Water Quality Control Handbook, 2nd ed. 2007, McGraw-Hill ; WEF Press: New York; Alexandria.
[26]   | Twort, A.C., Ratnayaka, D.D., and Brandt, M.J., (2002).Water Supply. 5th ed. Oxford: Butterworth-Heinamann; copublished by IWA Publishing.
[27]   | Waalkes, M.P., (2003). Cadmium carcinogenesis. Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, 2003. 533(1-2): p. 107-120.
[28]   | Joseph, P., (2009). Mechanisms of cadmium carcinogenesis. Toxicology and Applied Pharmacology, 2009. 238(3): p. 272-279.