PRELIMINARY WATER QUALITY EVALUATION OF THE VAISIGANO RIVER, SAMOA 1PATILA AMOSA, 2FAAINU LATU, 3TAEMA IMO, 4VAREA VAURASI 1,2,3,4ScienceDepartment, National University of Samoa, Samoa Email: [email protected], [email protected], [email protected], [email protected] Abstract - This study analysed water samples collected from Vaisigano River on Upolu Island, Samoa to evaluate the degree of pollution by nutrients, heavy metals and microorganisms. Samples were collected monthly from December 2016 to April 2017 at 3 sitesalong the river and analysed for dissolved oxygen (DO), biochemical oxygen demand (BOD),total - phosphorous (TP), nitrate (NO3 ), faecal coliform (FC), Enteroccoci (Ent) and the two heavy metals Cu and Pb. The results were used to calculate a water quality index (WQI) for each station with (WQIw) and without bacteria (WQIwt) to estimate the contribution of microbes to water contamination and to determine the overall health of each site. The WQIwvalues for the three stations ranged from (37.48 – 41.05)± 1.91 while WQIwtranged from (41.14– 59.03)± 9.14. All values were below 100 which is the critical value for surface water safety for use for human activities, aquatic life and wildlife survival.Based on the WQI values, water quality at the three sites wasgenerally poor. Keywords - Water quality index, pollution, microbial contamination, nutrients, Samoa I. INTRODUCTION studies conducted in the vicinity of Samoa on the quality of streams [9, 10] have shown only partial The impact of climate change on the quality of water compliance to established drinking water standards. resources and associated health implications has seen For example, of 44 streams analysed by [10] in an influx of research to assess the health of rivers. American Samoa, only 16% complied with water Water quality (WQ) describes the biological and quality standards for phosphorous. Analysis of physico-chemical characteristics of water in relation freshwater springs commonly used by communities in to its intended use(s),standards and criteria[1, 2]. Samoa showed total and faecal coliform levels way These surface waters may be contaminated by various above the recommended national and WHO limits human pathogens [3], excess nutrients[4] or heavy [11]. metals[5] washed into the waters during heavy rainfall events from mainly non-point sources.The The Samoan government vision for the 2016 – 2020 outbreak of water-borne diseases is a consequence of Strategy for the Development of Samoa [12]focuses consuming untreated tap water, bathing in and on “accelerating sustainable development and drinking water from sources polluted by various broadening opportunities for all” and stressing the wastewater microbes or eating contaminated need to “improve access to clean water that meet freshwater food [6]. national quality standards and promoting a healthy It is important for information from these Samoa”. In an effort to address part of this vision, a investigations to be presented in a manner that is preliminary assessment was conducted at Vaisigano clearly understood by policy makers for the river, one of the main catchments supplying the development of appropriate mitigation strategies, and reticulated system in the country to determine its also by local communities for awareness and correct physical, chemical and microbiological composition enforcement of measures to protect these resources. A and thereby health status. water quality index (WQI) summarises large amounts of data into a single value indicative of the water II. EXPERIMENTAL health. The main target of these indices is comparison with WQ standards so that the indices will determine 2.1. Study site whether the variable(s) comply with the standards or The Vaisigano Watershed in located on Upolu island, not and the frequency and the extent of exceedance Samoa(Figure 1) and receives an average annual for non-compliance [7]. The advantages of the WQI rainfall of about 4,277 mm, with average amounts of is its ability to integrate the measurements of all 2,923 mm and 1,515 mm respectively falling in the variables for water analysis in a single number, its wet and dry seasons [13]. It is about 3,700 hectares ability to combine different measurements in a large and feeds two treatment plants before diversion variety of different measurement units in a single into the reticulated water supply. Three sites were metric and its effectiveness as a communication selected for sampling to get a representative tool [8]. characterization of water quality. The three sites were The majority of streams in the tropical Pacific have located at Vaoala (V1,13.87°W, 171.75°S), Maagiagi not been scientifically explored for chemical and (V2,13.85°W, 171.75°S) and Malifa (V3,13.84°W, microbiological quality compared to streams in the 171.75°S). temperate and other tropical regions [9]. Fewer Proceedings of Academics World International Conference, Wellington, New Zealand , 7th-8th August 2018 1 Preliminary Water Quality Evaluation of The Vaisigano River, Samoa Figure 1. Study sites along the Vaisigano watershed on Upolu Island, Samoa(Source: MNRE Mapping Division]. 2.2. Materials and Procedures The FC and Entcontent of all water samples was Water samples were collected monthly at the three determined using the membrane filtration (MF) sites from December 2016 to April 2017.Five method following the protocols of [15]. This samples were collected at each site in sterilised250 ml procedure shows discrete bacterial colonies that can Schott bottles at a depth of about 10 cm below the be visually counted. Highly contaminated water water surface [14]. This sampling strategy reduced requires several sample dilutions in order to obtain the possibility of contamination from debris and filter plates with an appropriate range of colonies to bacteria deposited by wind on the surface water. validate enumeration. Preliminary measurements Samples were processed within 5 hours of sampling showed dense bacterial growth of raw samples hence for FC, Ent, BOD, nitrate, total phosphorous, copper all samples for the study period were serially diluted and lead.pH and DO were measured on site with a to 10-2 to obtain viable counts of bacterial colonies. handheld MP-103 pH/ORP/Temperature meter microprocessor-based waterproof DO/O2/Temp tester 2.3. WQI Calculations respectively. The health of the three sites was evaluated by calculating a WQI value based on the Canadian BOD was measured using a modified Winkler Water Quality Guidelines for the Protection of method [15, 16]and expressed as BOD5,the difference Aquatic Life [18] and using the median of replicate between the initial DO and the 5-day dissolved monthly measurements. This method requires a oxygen content after incubation of samples in the description of the water body and the number of sites dark at 20°C. TP was measured by means of the to be studied, measurement duration, variables which Ascorbic Acid Method (AAM) and using UV Vis should be at least four and research objectives. Spectroscopy. The concentration of nitrate, Cu and Although a minimum of one year is the recommended Pb were determined by spectrophotometric analysis duration, the method can still be applied to shorter using a Hach spectrophotometer and following the durations as with five months for this study. Cadmium Reduction Method (CRM), the The WQI is derived from the algorithm: Bicinchoninate Method 8506 and the PAR Method 10216 respectively [17]. ₁₂₃ WQI = 100 – ( )where . Proceedings of Academics World International Conference, Wellington, New Zealand , 7th-8th August 2018 2 Preliminary Water Quality Evaluation of The Vaisigano River, Samoa F1 represents the scope or proportion of variables that excursioni = − 1 do not meet standards, F2 denotes the frequency of non-compliant to the standards and F3 represents When the test value must not be less than the theamplitude or the amount by which the objective, measurements do not meet the standards. excursioni = − 1 The categorisation of water quality as shown in Table F1 = x 100 1 is based on the calculated WQI values and on the F2 = x 100 ranking of [18]. To estimate the contribution of microbial contamination on water quality, WQI F3 = .. values were calculated with (WQIw) and without nse (normalized number of excursions) (WQIwt) the microbial data. ∑ = 2.4 Data Processing and Analysis All statistical analyses were conducted using the statistics computer software package MINITAB 17 Excursion is the number of times a variable level is while WQI calculations were performed using greater or less than the standard. When the test value EXCEL 2016. must not exceed the standard, Table 1.Water quality ranking. WQI Category Excellent: Water quality is protected with a virtual absence of threat or impairment; 95 – 100 conditions very close to natural or pristine levels Good: water quality is protected with only a minor degree of threat or impairment; 80 – 94 conditions rarely depart from natural or desirable levels Fair: water quality is usually protected but occasionally threatened or impaired; 65 – 79 conditions sometimes depart from natural or desirable levels Marginal: water quality is frequently threatened or impaired; conditionsoften depart 45 – 64 from natural or desirable levels Poor: water quality is almost always threatened or impaired; conditions usually depart 0 - 44 from natural or desirable levels III. RESULTS AND DISCUSSION 3.1. Physicochemical characteristics The pH and concentration of the nine parameters investigated are summarised in Table 2. The mean pH of water was alkaline above 8.0 and within the accepted standard for drinking water. Nitrate and phosphorous in addition to atmospheric CO2 and acid rain contribute to the acidity of the rivers. With low levels of these compounds in water, the pH was expected to remain above neutral. Table 2.Statistical characteristics of physico-chemical and microbial composition of river water. Min=minimum; Max=maximum; AM=arithmetic mean; Med=median; Sd=Standard deviation; pH=no unit; Bacterial concentration in x103 cfu/100mL; units for all other parameters in mg/L.