## 1 Introduction  
Wastewater is generated from the industrial, domestic, commercial and agricultural sectors [1; 2]. Untreated wastewater contains various types of pollutants consisting of organic and inorganic materials with different concentrations [3], depending on the type of human activity that produces the wastewater. The water body can be contaminated when exposed to a high volume of wastewater and high concentration of contaminants [4]. The untreated wastewater should not be released into the environment because it contains harmful pollutants that can affect human health and ecosystem quality. Three-quarters of the organic carbon in wastewater presents as carbohydrates, fats, proteins, amino acids and volatile acids and inorganic pollutants including sodium, calcium, potassium, magnesium, chlorine, sulfur, phosphate, bicarbonate, ammonium salts and heavy metals [5]. Domestic wastewater generated from the household includes water from the sink, bathroom, toilet, washing machine and dishwasher. Industry and business centers also produced wastewater that must be treated before being released to the environment. Hazardous materials such as heavy metals and hazardous chemicals from the road surface, parking lot, roof and building can penetrate and pollute the river, lake and water body. Accordingly, treatment plants were built in every industry, factory and even residential area to treat wastewater. A treatment plant can help in reducing the pollutants in wastewater to the extent that the environment can be sustained and not harmed. However, most of the wastewater treatment technologies require high capital investment and also contribute to the problem of sludge disposal [6]. Thus, an environmentally friendly method of phytoremediation has been introduced as one of the wastewater treatment technologies. Phytoremediation uses green plants which make it an attractive biological treatment method [7]. Phytoremediation is a technology or method that used natural or genetically modified plants to remove, transfer, stabilize or reduce various pollutants contained in soil or water media [8]. The phytoremediation agents can remove organic and inorganic contaminants and interact with microorganisms [9; 10]. Wastewater treatment using a phytoremediation method offers several advantages, such as a cost-effective approach, minimum energy requirement, minimal environmental disturbance, conservation of soil biological activity, etc. [11]. Phytoremediation can also occur naturally in soil and water ecosystems [12]. This technology has been accepted in the last two decades as an environmentally friendly and low cost approach in wastewater treatment. According to [PERSON] [13], the use of plants for the recovery of soil and water which was contaminated with heavy metals have been proved to be effective. [PERSON] and [PERSON] [1] found that lake water treatment using aquatic plants was beneficial to improving water quality, with high efficiency in reducing chemical oxygen demand (COD). Table 1 shows several previous studies that were conducted in Malaysia on the removal of TSS, NH\({}_{3}\)-N and COD by phytoremediation treatment. In Malaysia, the use of plants to treat polluted water or soil has gained popularity. Many studies have been conducted to study the capability of the plant in reducing different types of contaminants in soil or water, and the research outputs can be practiced in various sectors [14; 15; 16]. To date, phytoremediation is not only important for universities and research centers, but also creates new business for contractors and consulting firms. The objectives of this study were to determine the water quality before and after treatment, to determine the rate of reduction in total suspended solids (TSS), ammoniacal nitrogen (NH\({}_{3}\)-N), and COD in sewage wastewater through the phytoremediation method by _Lemma minor_, _Salvinia minima_, _Ipomoea aquatic_ and _Centella asatica_, and also to evaluate the effectiveness of these plants in the phytoremediation of sewage wastewater.