## 3 Results and Discussion
[35], the original content of LNA cells in the rainwater may have been shifted to HNA cells as a result of the nutrients fed from the effluent, which allowed the bacterial population to actively grow and reproduce in the system. This condition is supported by the increasing trend of the physicochemical properties as the POME final discharge was being introduced into the system from day 2 to day 7. The condition is reflected in the TSS and VSS content which slowly increased until it reached 47.9 \(\pm\) 1.9 mg/L (Figure 4d) and 33.64 \(\pm\) 1.42 mg/L (Figure 4e) on day 7, respectively. Since the POME final discharge contains nutrients (Figure 4b,c), it contributes to the growth of the bacterial community that are carried together in the suspended solids [36]. Similarly, the COD and BOD\({}_{5}\) concentrations rapidly increased to 90.0 \(\pm\) 5.0 mg/L (Figure 4f) and 27.2 \(\pm\) 11.1 mg/L (Figure 4a) on day 2, respectively, and continued to progressively increase until day 7. These results prove that the introduction of POME final discharge into the clean water caused water pollution, and increased the proportion of viable bacteria and hence the HNA proportion of bacterial cells. Nonetheless, the proportions of the viable bacterial cells and HNA were reduced once the zero-emission of POME final discharge was introduced from day 8 to day 15. This condition was expected since the increase in the proportion of viable cells was mostly contributed to by the addition of POME final discharge into the system. Hence, after POME final discharge stopped being added into the system, the proportions of viable bacterial cells and HNA cells decreased as the system progressed until day 15. A decreasing trend in the physicochemical properties could be observed once the zero-emission system of POME final discharge was implemented. These results correlate well with the reduction in the nutrient contents present in the system following the implementation of zero-emission of POME final discharge (Figure 4b,c). The TSS and VSS concentrations also gradually decreased until they reached 6.75 \(\pm\) 3.04 mg/L (Figure 4d) and 6.92 \(\pm\) 1.4 mg/L (Figure 4e), respectively, on day 15. A similar finding was previously reported where the TSS and VSS concentrations in the municipal effluent were able to be reduced following the implementation of a zero-emission system [11]. Similarly, the COD (Figure 4f) and BOD\({}_{5}\) (Figure 4a) concentrations were gradually reduced following the implementation of zero-emission of POME final discharge from day 8 to day 15. The previous study had reported that the COD concentration of the polluted river decreased once the dyeing wastewater was no longer released into the river [37]. The river that was previously contaminated by urban pollutants also showed a positive reduction in the BOD\({}_{5}\) concentration after its reclamation process [38]. This primary result shows an interesting outcome where the bacterial cell's viability and the HNA proportion in the artificial river water system shifted following the implementation of zero-emission of POME final discharge, as reflected also in the physicochemical and nutrient content analyses. Therefore, this condition suggests that the bacterial community in the receiving water system had greatly recovered following the implementation of zero-emission of POME final discharge. Effect of Zero-Emission of POME Final Discharge on the Composition of the Bacterial Community in the Receiving Water System  
The changes in the taxonomic composition at the phylum level before and after the implementation of zero-emission of POME final discharge are summarized in Figure 5, after the relative abundances at below 1% were cut off. The rainwater and POME final discharge were dominated by Proteobacteria phylum with compositions of 52.5% and 35.8%, respectively, followed with Bacteroidetes with a respective composition of 20.4% in the rainwater and 15.8% in the POME final discharge.