**4. Conclusion**

Groundwater is essential especially in island areas that lack surface water resources. This study which has been conducted in Kapas Island, Marang Terengganu have shown that the groundwater quality was in Class II and III of the slightly polluted status. With the classification obtained, the groundwater in Kapas Island requires conventional treatment for Class II and intensive treatment for Class III. This is because the use of groundwater is not recommended to be directly consumed as drinking water because it contains contaminants from the underground aquifer system during the water pumping process. However, it is still suitable for uses that involve body contact as well as for animal drinks without the need for prior treatment. Therefore, accommodation centers that channel groundwater to be used in tourist accommodation areas should emphasize its use, especially in the process of providing food and beverages to visitors to avoid them from getting sick due to the groundwater.

The determination of WQI status was assessed based on six main parameters that include DO, COD, BOD, SS, NH3-N and pH tests. Out of six parameters, the parameter with the worst pollution of groundwater quality was the NH3-N parameter because it exceeded the standard set. The NH3-N value obtained above this standard was 3.5 mg/l at S2 during the NEM which is in Class V with a highly polluted status. The DO, pH, COD, TSS parameters showed a safe class which is Class I. All stations for DO, pH, COD and TSS parameter tests were below the set standard with an average value of > 7 mg/l for DO, > 7 for pH, < 10 mg/l for COD and < 25 mg/l for TSS. The classification of the obtained parameters was in Class I, so it can be concluded that the groundwater quality in Kapas Island is free from pollution that is for the DO, COD and TSS parameters.

Based on the groundwater quality analysis, it was explained that the status of groundwater quality was safe for external use that included body contact such as bathing, washing, and so on. However, if it is to be used as drinking water and for food preparation, it should be first be given conventional and intensive treatment before use. The lowest WQI value obtained for groundwater quality in Kapas Island was 61%. This value has recorded a Class III of moderately contaminated status but is still safe for external body use and also safe to be used as a drinking source for animals.

*Seasonal Variability of Groundwater Quality in Kapas Island, Terengganu, Malaysia DOI: http://dx.doi.org/10.5772/intechopen.99863*
