2.4 impacts of waste stabilization ponds
waste stabilization ponds enable the achievement of the required degree of purification at lowest cost and with minimum maintenance by unskilled operators mara: 2003 this was echoed by naddafi: 2008 who stated that waste stabilization ponds are commonly used as efficient means of wastewater treatment relying on little technology and minimal albeit regular maintenance. thus if waste stabilization ponds are properly used there is maximum removal of impurities with the use of minimal resources. waste stabilization ponds have been determined to be able to considerably remove pathogens found in waste water. potential pathogens in wastewater effluents include various genera of bacteria, viruses, protozoa and helminthic ova and the disinfection quality is evaluated through the assessment of indicator organisms namely escherichia coli, faecal coliforms or total coliforms liu: 2017 reinoso 2011 also highlighted the same sentiments when he said that waste stabilization ponds have been considered as well established methods of biological waste water treatment particularly being effective in the scrapping of pathogens. The most important aspect for most stringent control over wastewater use in agriculture is the risk exposed to human health of irrigators consumers of produce and the general public (Scott, 2005). Monitoring waste water is also done because studies have revealed that the release of wastewater from hospitals was associated with an increase in the prevalence of antibiotic resistance elmanama: 2006 waste stabilization pond effluent is rich in nutrients and consequently attractive for use in irrigation. waste stabilization ponds attenuate organic and nutrient loads and have been reported to achieve excellent pathogen removal efficiencies through naturally occurring biological chemical and physical treatment mechanisms bolton: 2010 in nigeria the existence of waste stabilization ponds has often encouraged wastewater reuse in unrestricted irrigation. Agunwamba 2001 noted that wastewater irrigation is a means of livelihood for the urban poor from communities close to the university of nigeria but the indiscriminate reuse also contributed to health hazards and soil degradation. Most industrialized countries currently rely heavily upon mechanical treatment to increase the quality of the water emitted from their wastewater facilities while those techniques generate excellent treatment and high-quality water they can be expensive to maintain and they require costly upgrades when the population expands the presence of waste stabilization ponds creates some problems either on operations or on the immediate environment. This can be witnessed in Arak where the basic wastewater treatment process done is through the use of waste stabilization ponds. however due to inappropriate design and consideration of both biological process and physical aspects of the ponds the existing facilities suffer serious malfunctioning problems naddafi: 2008 these malfunctioning problems may result in the waste stabilization ponds not properly treating the waste water which may in turn lead to contamination of the surrounding environments. joshua 2017 noted that several studies have indicated that wastewater effluents still contain high amount of faecal coliforms which do not conform to the 1000cfu/100 ml in the guidelines for wastewater discharge. moran 2017 found that there are three principal reasons for waste water treatment plant failure which are a poor specification failure to consider all relevant local factors at the pre-design stage and poor operational standards. in new zealand it was noted that the municipal wastewater discharge causes a conspicuous change in the colour clarity of the receiving water and significant increases in suspended solids bod and dissolved reactive phosphorous at a distance of 50 metres downstream from the discharge point under low flow conditions niekerken: 2005 wastewater discharges may pose water quality risks to downstream ecosystems and people who rely upon the river as drinking water source chen: 2009 but it simultaneously provides a renewable and sustainable in stream flow that contributes towards a reliable water supply mohamad: 2014 the presence of treated waste water in drinking water supplies increases the risk of water quality contamination from pharmaceuticals or other trace organics pathogens and inorganic pollutants schwarzenbach: 2010 wastewater treatment pond discharges are a main source of pharmaceuticals and many other micro pollutants in the environment nutrients that influence stream ecology and pathogens that pose ecological and human health risks maier et al: 2015 wastewater treatment is coming under increasing scrutiny and pressure to improve as concerns are raised about the health risks that microorganisms like bacteria, protozoa and viruses in wastewater pose to aquaculture tourism and recreational water if they are not adequately removed niekerken: 2005 wastewater has also been implicated as a possible source of heavy metals polycyclic aromatic hydrocarbons and microbial contamination to soils surface water sediment and groundwater song: 2006 the risks of waste water to the environment were also articulated by agunwamba 2001 who discovered that the reuse of the university waste stabilisation pond effluent in irrigation of crops especially vegetables has often raised public outcry and the disapproval was aggravated by the endemic nature of typhoid fever and diarrhoea in the surrounding area of nsukka as the effluent quality is very poor. the ponds are good for the growth of aquatic insects dehgani: 2007 some of the insects include mosquitoes and flies which are known vectors of communicable diseases such as malaria and cholera.
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2.5.1 anaerobic ponds
These are the first ponds and are the recipients of the influent from residential and industrial areas and are thick and dark in colour. They are tasked with anaerobic respiration so they are mainly concerned with the presence of anaerobic bacteria that digests in the wastewater which is highly organic at this stage. They are the deepest of the ponds since anaerobic bacteria do not need oxygen and sunlight in order to digest. (Mara 2004) concurred by suggesting that these ponds are normally deeper due to sludge accumulation and the main function is to remove biological oxygen demand in a relative short retention time of few days. Organic particles are removed by the sedimentation of settable solids and anaerobic digestion in the sludge layer. Theoretically, anaerobic systems should generate lesser amounts of sludge compared to aerobic systems however in practice in areas such as the Australian meat process industry, anaerobic ponds frequently fill rapidly with solids (Watson: 1999). Anaerobic ponds are commonly used for treatment of industrial and agricultural wastes which contain high organic matter and sulphates (Rhajbhandari, 2007). Anaerobic ponds provide a degree of pre-treatment thereby enabling a reduction in the size requirements of the subsequent aerobic ponds. Anaerobic treatment is more suited to wastewater that contains high bod (UNEP, 2002) and is therefore useful at reducing high values of bod and suspended matter from agricultural and food processing wastewater. An adequately designed anaerobic pond can achieve around 60% bod removal at 20° c and one-day hydraulic retention time is sufficient for wastewater with a bod of up to 300 mg/l and temperatures higher than 20° c (Mara, 2003). The anaerobic ponds act mostly like an uncovered tank that breaks down the organic material in the effluent through the use of organisms that release methane and carbon dioxide (Quiroga, 2014). The main operational problems of anaerobic ponds are the odour problems, mosquitoes and other insects and the possible reasons of odour problems are excessive loading rate presence of toxic substances and inhibitors in influent sudden drop of temperature and low influent ph value (Marinella, 2015). When considering the effects on climate change, another disadvantage of anaerobic pond systems is the emission of greenhouse gases such as methane, carbon dioxide and nitrogen oxide that are normally released to the atmosphere since the areas are open and need sunlight and wind to operate (Glaz: 2016).
figure 4 diagram showing different types wastewater ponds namely anaerobic facultative and maturation ponds

2.5.2 facultative ponds
These are the largest of the waste stabilization ponds and they harbor both aerobic and anaerobic bacteria and Shelton (2005) concurred that they are referred as fulcatative ponds because the term facultative refers to the fact that these ponds operate with both aerobic and anaerobic zones. Reed 91995) said that a facultative pond is the greatest common type used in the United States of America with other terms such as oxidation ponds, sewage lagoon and photosynthetic ponds. According to Palacios (2014), the waste water treated in the aerated ponds is discharged into the facultative ponds which need to fulfill two fundamental requirements of fulcatative ponds which are to have an adequate organic capacity and an oxygen balance that keeps the aerobic conditions over the anaerobic layer situated in the bottom of the pond. The availability of algae in the aerobic and facultative zones is vital for the successful performance of facultative ponds (EPA, 2002). In sunlight conditions, the algal cells utilize carbon dioxide from the wastewater and release oxygen produced during photosynthesis. The oxygen produced by algae and surface reaeration is then used by aerobic and facultative microorganisms to stabilize organic material in the upper layer of water. Fulcatative ponds can be broadly classified as primary or secondary based on the components of the influent. If the facultative pond receives influent without pre-treatment it is named as primary facultative pond whereas if the fulcatative pond receives pre-treated influent from anaerobic pond septic tank or shallow sewerage systems it is called a secondary facultative pond (Sperling, 2007). According to Environmental Protection Agency (2002), facultative ponds are usually 1.2 to 2.4 m in depth and are not mechanically mixed or aerated. The wastewater is more greenish and this signals the abundance of algae in water. They are designed for BOD extraction due to a relatively low surface loading to allow the growth of a healthy algal population since the oxygen for BOD removal by the pond microorganism is mostly created by algal photosynthesis (Mara and Pearson, 1998). The algae is crucial to the process as it uses the carbon dioxide produced by aerobic bacteria to develop and release more oxygen which is consumed by the available aerobic bacteria for survival. This interrelationship between algae plants and aerobic bacteria is called symbiosis and allows for the removal of nutrients, heavy metals and pathogens (Alamgir, 2016).

2.5.3 Maturation ponds
The effluent from fulcatative pond is channeled into the maturation ponds. The main intention of maturation ponds is to remove hazardous microorganisms found in the wastewater. These are very shallow usually 0.9 1m deep in order to allow light to pass through to the bottom and aerobic conditions throughout the whole depth (Dehgani, 2007). The maturation ponds have a similar purpose than the facultative ponds with the difference being that in maturation ponds there is hardly any accumulation of matter and the increase of the pH due to photosynthesis activity results in an important bacterial mortality. Kayombo (2015) also added that maturation ponds usually show less vertical biological and physicochemical stratification and are well fed with oxygen throughout the day. The amount and size of maturation ponds is defined by the necessary retention time required for the removal of faecal coliform and it should also be noted that maturation ponds also perform the oxidation of a small amount of biological oxygen demand (Martinez, 2014). Total nitrogen removal in a whole waste stabilization system depends on the number of maturation ponds included in the waste stabilization ponds system (Pena, 2004).

Groundwater contamination
National Centre for Groundwater defines groundwater as water that is found beneath the earth’s surface and it is an important source of drinking water especially in the rural areas (Rotatu, 2008). It is also fresh water from rain or melting snow and ice that soaks into the soil and is stored in the tiny pores between the rocks and particles of soil (EPA, 2018). The quality of groundwater is determined by various chemical constituents and their concentrations which are mostly derived from the geological data of the particular region through groundwater flows (Khumbar, 2011). Human activities can change the natural composition of groundwater through the disposal of chemicals and microbial matter on land or into the soils and this can lead to groundwater contamination which is the change of groundwater quality due to the activities of man (Harter, 2003). The sources of groundwater contamination can be natural in nature whereby naturally occurring particulates of the soil such as iron fluorides manganese arsenic chlorides or sulphates can become dissolved in ground water. Other naturally occurring substances such as decaying organic matter can move in ground water as particles (EPA, 2018). Man-made or human activities also promote groundwater contamination. Activities such as agricultural development, surface water irrigation,chemical use in agriculture urban and industrial development affect the quality and quantity of groundwater as well (USGS, 2016) in Jordan, Al Ramtha wastewater treatment plant was discovered to be the main cause of groundwater contamination and high levels of nitrates were found on nearby wells obeidat