## 3 Results and Discussion  
### Initial Parameters for Water Quality Prior Treatment  
The results of preliminary data on water quality in the study area found that the average temperature reading for the sewage wastewater samples was 26.77 \({}^{\circ}\)C and the average reading of pH was 7.33. The pH of sewage wastewater showed an alkaline value because the samples were collected at a sewage treatment plant at a residential area which may contain wastes such as soap, urine and detergent generated from the household activities. The average reading of DO content was 3.19 mg/L. The low value of DO in the study area was due to the high amounts of bacteria and excessive amount of BOD from the untreated sewage which used DO. DO refers to the level of free oxygen, which does not accumulate in water or other fluids. It is an important parameter in assessing water quality because of its influence on living organisms in water body. Too high or too low a level of DO can endanger the aquatic organisms and affect the water quality [17]. The mean value of the TSS of the sewage water was 83.33 mg/L. The TSS value was influenced by the presence of algae and also the presence of soil in the water body. When it rains, soil from the surrounding area will enter the water body and cause an increase in suspended solids volume. TSS is a particle larger than two microns in a water body. The suspended solids were made up of inorganic materials, bacteria and algae. Organic particles from the decomposition materials can also contributed to the increase in suspended solids volume. When algae, plants and animals decompose,  
Figure 1: The phytoremediation treatment performed in the laboratory using (**a**) _Lemma minor_, (**b**) _Salvinia minima_, (**c**) _Ipomoea aquatica_ and (**d**) _Centella asiatica_. the decomposition process allows small organic particles to enter the water body as suspended solids. TSS is an important factor in determining the purity of water. The higher the amounts of suspended solids present in the water, the cloudier the water [26]. The average reading for COD was 40 mg/L. COD value was related to the DO parameter because a higher COD value means more organic matter was oxidized in the water which will reduce the DO level. COD is a measure of the oxygen required to oxidize the dissolved materials and organic matter in water [27]. It is an important water quality parameter as it provides an index to assess whether the discharged sewage will have an impact on the environment. The average value of BOD recorded was about 26 mg/L. BOD represents the amount of dissolved oxygen needed by microorganisms in the aerobic process of the decomposition of organic matter. BOD was used as an indicator to determine the amount of organic pollutants in most aquatic ecosystems [28]. The permitted limit for BOD issued by the Department of Environment (DOE) in Malaysia is 50 mg/L. A low BOD value indicated a good quality, whereas a high BOD value indicated a contaminated water quality. Finally, the average content of NH\({}_{3}\)-N in the sewage sample was 10.20 mg/L. NH\({}_{3}\)-N is a common pollutant in a domestic wastewater which results from the degradation of nitrogenous organic matter. The degradation of organic matter in the biological treatment stage also produced a large amount of ammonia compounds [29]. The Environmental Quality (Sewage) Regulations 2009 has been revised by the DOE Malaysia, which significantly reduced the limit for the released of NH\({}_{3}\)-N from 50 mg/L to 5 mg/L. Sewage wastewater which contains high ammonia nitrogen will prevent the natural nitrification and reduce the water purification capacity and consequently endanger the water environment. Excess nitrogen released into the water body can contribute to eutrophication and rapid growth of algae, which results in a reduction of oxygen in water. Figure 2 shows the preliminary data on the water quality of sewage wastewater samples in this study.