Physico-chemical properties and pollution status of the rivers at Konaweha watershed, Southeast Sulawesi

The Lasolo - Konaweha watershed is a river area in Southeast Sulawesi, Indonesia. It is a source of water for various sectors including irrigation and non-irrigation needs, and functions as a source of drinking water for several communities and industries. However, population growth and human activities have led to water quality degradation in the area. Many methods of determining water quality status have been developed, one of them is the pollution index (PI) method. The purpose of this study was to evaluate the characteristics of physico-chemical and determine the pollution status of the Lasolo – Konaweha watershed. The study utilized secondary data from the Hydrology and Water Quality Unit of the Sulawesi IV River Basin Center in Kendari, collected in 2020. The water quality data were analyzed according to the Government Regulations of Republic Indonesia No. 22 of 2021, and the pollution status was determined using the pollution index (PI) method. The water quality data were compared spatiotemporally using analysis of variance (ANOVA). The study found that several parameters were outside the water quality standards, including pH, total suspended solids (TSS), dissolved oxygen (DO), chemical oxygen demand (COD), methylene blue active substances (MBAS), and phenol. These parameters indicated a moderate to heavily polluted status for the Lasolo - Konaweha watershed. The study also found a strong correlation between water discharge and conductivity.


Introduction
The Lasolo -Konaweha watershed is a river area located mainly in the Southeast Sulawesi Province.According to the results of the Plenary Session of the Water Resources Management Coordination Team of the Lasolo -Konaweha river area, the current allocation of water in the area is for both irrigation and non-irrigation purposes, such as for the PDAM Kab.Konawe, PDAM Tirta Anoa, PT Utama Agrindo Mas industrial intake, and the PT Virtue Dragon Nickel Industrial Park (VDNIP) [1].As the population and the community's economy continue to grow, the demand for water in various sectors also increases.
In the Lasolo -Konaweha watershed, erosion and sedimentation pose a threat to the sustainability of water resources and the benefits of water resource development and management efforts.The high suspended material carried by the high rivers in the area is not suitable for water sources used by the PDAM and industrial intakes.Rivers are open bodies of water that receive inputs from all discharge sources derived from human activities in the surrounding region.These discharges can alter physical, chemical, and biological factors in the waters, leading to changes in water quality [2].To assess water quality, several indexing methods have been developed including the pollution index (PI) method, which is considered in the Ministry of Environment Decree No. 115 of 2003.These methods involve comparing the results of monitoring with available standards [3] [4].
The pollution index is a tool used to conclude the status of water quality.It assesses source water quality by comparing it to established quality standards.The water quality status is determined by the presence of physical substances and bacteriological boundaries [5].In 1970, the National Sanitation Foundation of the United States (NSF) created the widely used Water Quality Index (WQI), which uses nine significant limits to represent water quality status [6].This study aimed to evaluate the physicochemical characteristics and determine the pollution status of the Lasolo -Konaweha watershed.

Material
The study used secondary data of water quality monitoring data in the Lasolo-konaweha watershed carried out by the Hydrology and Water Quality Unit of the Sulawesi IV River Basin Center, Kendari on 2020 [7].There are nine sites in the Lasolo-Konaweha watershed area collected for July and September as shown in Figure 1.

Data analysis
Physico-chemical examination had been conducted on 10 water quality parameters including conductivity, temperature, turbidity, total suspended solid (TSS), pH, dissolved oxygen (DO), chemical oxygen demand (COD), nitrate, ammonia, total phosphate, detergent (MBAS), and phenol.Data on water quality was calculated to determine the level of river contamination.Based on purpose, water quality standard in National Government Regulations of Republic Indonesia No. 22 of 2021 is categorized into four classes: Class I (drinking water); Class II (infrastructure, recreation, cultivation of freshwater fish, livestock, irrigation); Class III (freshwater fish farming, animal husbandry, irrigation); and Class IV (irrigation) [8].The following is a formula for calculating the PI value.
Notes: PI: Pollution Index; Ci: concentration of water quality parameters i; Lij: concentration of water quality parameters i stated in the water quality standard; m: maximum; r: average Data analysis used to compare spatiotemporally is Analysis of variance (ANOVA) at a 95% confidence level (alpha of 0.05).To see a significant relationship between water quality parameters, a correlation analysis was carried out.

Result and Discussion
From the results of monitoring data recapitulation, it can be seen that most of the water quality parameters show values according to river water quality criteria in Government Regulation of Republic Indonesia No. 22, 2021, except for MBAS and phenol concentrations.The results of the analysis for Lasolo -Konaweha watershed data monitoring are presented in Table 1.

Conductivity and turbidity
Conductivity or electrical conductivity (EC) is a measure of a solution's ability to conduct an electric current.EC can also be interpreted as an indirect measure of the saltiness of the water.The more dissolved salts that can be ionized, the higher the conductivity value.Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulphate, and phosphate anions or sodium, magnesium, calcium, iron, and aluminium cations [9].The conductivity values in the study site ranged from 0.4-302 µmho value of 108.10 µmho and the SD of 28.91 (Table 1).Figure 2 showed the highest value was found at Station Asera (293.5 µmho).The maximum limit in drinking water is prescribed as 1400 mS/cm (WHO, 2003).This implies that the conductivity value is still within normal limits.The results of the significance test show that there is no difference between the observation time and the varied of sampling location (P >0.05).Water turbidity is a significant parameter that affects the penetration of light in the water thereby affecting aquatic life [10]  .Figure 2 shows that the average value of the water turbidity in the Lasolo -Konaweha watershed has exceeded the quality standard threshold.There was no significant difference between the sampling time and sampling locations (P >0.05).

Total suspended solid and pH
The total suspended solids generally represent the content of organic matter in water.Based on the class II water quality criteria, Government Regulation No. 22 of 2021, the tolerance value for TSS concentration is 50 mgL-1.In Figure 2 it can be seen that the concentration of TSS at the study site is outside the water quality criteria (85-228 mgL-1).The analysis results showed no significant difference in the sampling time (p> 0.05).In an aquatic system, pH is a significant parameter of the water quality.Kumar et al. (2011) revealed, pH is an important indicator in assessing the pollution level of a watershed area.The water pH of Lasolo-Konaweha watershed in 2020 ranged from 5.0 -5.9.pH values tend to be low and outside the class II water quality standards.This is thought to be caused by an increase in organic matter which will release CO2 when decomposed.The pH value in the waters is also related to the concentration of DO and carbon dioxide, where the pH value will decrease as the DO value decreases.

DO and COD
DO greatly affects the life of aquatic biota and biological processes.In water body, DO concentration is influenced by temperature, salinity, and organic matter entering the river [13].The monitoring data showed that the DO concentration in the study site did not meet the quality standard for Class II water quality of 4 mgL-1.DO concentration decrease occurred even reaching anoxic conditions.The DO of the Lasolo-Konaweha watershed in 2020 ranged from 0.2-1.9mgL -1 .There were significant differences between sampling times (P< 0.05) and relatively the same concentration at each sampling time (P >0.05).Low DO values in river bodies indicate high organic matter content.DO is needed to decompose organic matter.Domestic waste that has a high COD value is due to the high amount of [14].
COD describes the quantity of oxygen needed to chemically oxidize organic matter.COD values in the study area ranged from 40.0 to 46.8 mgL-1.Statistical analysis showed that there was no significant difference in the sampling time.

Nitrate and ammonium
The presence of nitrogen in the waters comes from residual fertilizer runoff from an agricultural area and industrial waste disposal [15,16].Concentrations of NO3-N in the Lasolo-Konaweha watershed in 2020 were detected in the range of 1.5-5.7 mgL -1 (Figure 4).All of these locations still fulfilled the standard in accordance with water quality criteria Class II PP 22/2021 at 10 mgL -1 .There were        Another nitrogen compound that functions as a nutrient for plants is ammonia.The ammonia content in water derived from the dissolution of fertilizers, animal waste, and others.High ammonia content in water will increase the growth of aquatic plants so that the oxygen content in the water will decrease and cause aquatic animals to be difficult to grow and even die.NH3-N was detected in the Lasolo-Konaweha watershed in 2020 ranging between 0.01-0.14mgL -1 (Figure 4).Generally, the value of ammonia concentration in the Lasolo-Konaweha watershed still meets the water quality criteria Class II PP 22/2021 at 0.1 mgL-1.Statistical analysis showed not significant difference between the sampling time of and the sampling location (P > 0.05).

Total phosphate
The maximum allowable concentration of total phosphate in river waters has been reported to be 0.1 mgL -1 [17].Phosphate concentration of 0.025 mg/L can accelerate the eutrophication process in rivers [18].The total phosphate detected in the Lasolo-Konaweha watershed 2020 ranged from 0.01-0.12mgL - 1 (Figure 4).The average value of phosphate concentration at the study site shows that it still meets the water quality criteria Class II PP 22/2021 at 0.2 mgL -1 .There was no significant difference either for sampling time or sampling locations (P > 0.05).

MBAS and Phenol
MBAS (Methylene Blue Active Substances) is one of the anionic surfactants derived from urban and sub-urban activities (utilization of soap and detergent, motor vehicle emission, biomass combustion ) that are disposed to surface water.MBAS often contains nutrients such as nitrogen and phosphate which can induce algae blooming.MBAS in the study site was detected in 2020 with a range of 15.0-39.6 mgL -1 .In most study areas, MBAS were detected above the water quality criteria class II of Government Regulation No. 22/2021 of 0.2 mgL -1 .There were no significant differences between sampling time and sampling location in terms of MBAS.(P <0.05) (Figure 8).Phenol concentration in the waters of the Lasolo-Konaweha watershed ranged from 0.09 to 0.60 mgL -1 with an average of 0.27 mgL -1 .While the required phenol concentration in the water quality criteria class II Government Regulation number 22/2021 is 0.005 mgL -1 .This indicates that the phenol content at the observation site has exceeded the water quality criteria.This situation makes the observed river water area not feasible for consumption because it is harmful to health and will greatly affect the polluted river ecosystem [19].Sources of phenolic pollutants come from industrial activities and domestic waste is also the dominant pollutant.There were no significant difference on the sampling time and the sampling locations (p >0.05).

Pollution status
One of the methods used to determine the status of water quality is the Pollution index.A water quality status represents the level of the source water quality by comparing the quality standards that have been set.The pollution index value can be seen in Figure 6.Based on the Ministery of the Environment Decree No. 115 of 2003 regarding Guidelines for Determining the Water Quality Status based on the pollution index, it can be seen that the Amesiu and Polo Polara stations have heavily polluted water quality status, with the pollution index value >10.Meanwhile, other stations have moderately polluted quality status (5<PI<10).Amesiu and Polo Polara stations are located downstream from the Konaweha watershed where there are already many settlements that have the potential to pollute river water.

Correlation among the Physicochemical Parameters of the Lasolo -Konaweha watershed
The t correlation coefficient describes whether or not the linear relationship between variables is strong.Correlations among the physicochemical parameters of analyzed water samples from the Lasolo-Konaweha watershed is presented in Table 2.There was a strong positive correlation between water discharge with conductivity.The water flow carries materials both organic and inorganic from the land into the river body.These materials are in the form of anions and cations that can conduct electricity.A strong positive correlation was also shown between pH to turbidity.The concentration of pH in water is also influenced by the level of turbidity.Therefore, if the water is too acidic or alkaline then the level of turbidity of the water will also be high.

Conclusion
Based on the result obtained, the water quality parameters analyzed for the sampled water included pH, TSS, DO, COD, detergent (MBAS), and phenol are not in accordance with the class II criteria in government regulation no.22/2021.However, other parameters still met the water quality criteria.

Figure 1 .
Figure 1.Map of the research location and sampling locations.
(Verma and Saksena 2010; Tambekar et al. 2013).Water turbidity is the reduction in transparency due to the presence of particles such as clay or silt, chemical precipitates such as manganese and iron, finely divided organic matter such as plant debris and organisms, plankton, and other microscopic organisms (APHA/AWWA/WEF, 2012).The turbidity of the study site ranged from 0.5-130 mgL-1 with a mean of 63.64 mgL-1, SD 28.91.According to The Regulation of The Ministry of Health of the Republic of Indonesia No. 32 of 2017, the water quality standard for sanitation hygiene purposes is 25 NTU or 8.3 mgL-1 [12]

Table 2 .
Correlation matrix for water quality parameters in the Lasolo -Konaweha watershed.