## 2 Wastewater Treatment by Microalgae
### Domestic Wastewater
#### 2.1.3 Microalgae Treatment of Domestic Wastewater  
There have been several pieces of research published in the literature that have investigated the feasibility of treating sewage, kitchen and toilet wastewaters with or without dilution using microalgae. Culture conditions, initial nutrients concentrations and removal rates have been gathered in Table 3 for different microalgae and domestic wastewater treatments, while the growth parameters and metabolites production of microalgae culture in domestic wastewater are provided in Table 4. Figure 2 showed that each species of microalgae has a different capacity to reduce pollutants from domestic wastewater, and this ability varies from one wastewater to another. The maximum potential for total nitrogen (TN) and total phosphate (TP) removals from municipal wastewater were found for _Chlorella variabilis_ TH03 at a 96.8% and 100% removal rate [37]. The other microalgae removed between 28% and 95% of total nitrogen and between 12% and 99% of total phosphate. The removal efficiency of chemical oxygen demand was not assessed in the majority of these studies. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Wastewater** & **Pretreatment Method** & **Microalgae** & **References** \\ \hline Domestic & Filtered ([PERSON] filter paper, grade 1), autoclaved & _Chlectoxs_ sp. and _Isochrysis_ sp. & [35] \\ Municipal & Settled in flask for two hours and pretreated by passing & _Chlorella minutilsim_ & [23] \\ Domestic & Filtered using a 0.2 \(\upmu\)m nylon membrane filter & _Scendesmus_ sp. & [36] \\ Domestic & Filtered through a mesh sieve (100 \(\upmu\)m) & _Chlorella_ sp. and _Scendesmus_ sp. & [24] \\ Domestic & Pre-filtered using filter cloth (nyion monofilament, pore size & _Chlorella variabilis_ TH03 & [37] \\  & 25 \(\upmu\)m) and autoclaved at 121 \({}^{\circ}\)C for 20 min & _Chlorella_ variabilis_ TH03 & [37] \\  & Centrifuged at 5000 rpm for 15 min, filtered by 0.45 \(\upmu\)m & _Chlorella_ pyrenoides_ (FACHB-9) & [33] \\ Septic tank & polyester filters and sterilized by an autoclave for 20 min & _Chlorella_ yrenoides_ (FACHB-9) & [33] \\  & at 121 \({}^{\circ}\)C & _Chlorella_ variabilis_ (UTEX 1230) & [22] \\ Municipal & Filtered using LLG-filter papers (pore size 5 \(\upmu\)m to 13 \(\upmu\)m) & _Chlorella_ _sorchiiman_ (UTEX 1230) & [22] \\ Municipal & Filtered with a 2 \(\upmu\)m filter & _Phaodactylulum tricemutum_ & [28] \\ Domestic & Filtered using nylon mesh with pore size \(\sim\)50 \(\upmu\)m & _Botryococcus_ sp. & [14] \\ Domestic & Filtered & _Chlorella_ sp. & [12] \\  & Autoclaved at 121 \({}^{\circ}\)C for 30 min & _Chlorella_ _pyrenoides_ & [19] \\ Municipal & Filtered and autoclaved at 121 \({}^{\circ}\)C for 20 min & _Chlorella_ _zofingiensis_ & [31] \\ Municipal & Filtered through glass microfiber filters with 0.6-\(\upmu\)m pores & _Dunaliella salina_ & [38] \\  & and autoclaved at 121 \({}^{\circ}\)C under 15 psi for 20 min & _Chlorella_ _pyrenoides_ & [20] \\ Domestic & Autoclaved at 121 \({}^{\circ}\)C for 30 min & _Chlorella_ _pyrenoides_ & [20] \\  & Filtered and sterilized using vacuum filtration unit and & _Nammochloropsis acamica_ & [32] \\  & autoclaved at 121 \({}^{\circ}\)C for 15 min & _Chlorella_ _valgaris_ and _Nammochloropsis aculata_ & [34] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Pretreatment methods of domestic wastewater before microalgae cultivation. Recently, [PERSON] et al. 2019 [12] explored the treatment of kitchen wastewater (Phosphates: 2.037 mg L\({}^{-1}\); Nitrates: 52.962 mg L\({}^{-1}\); COD: 560 mg L\({}^{-1}\)) and sewage wastewater (Phosphates: 1.7 mg L\({}^{-1}\); Nitrates: 30.25 mg L\({}^{-1}\); COD: 784 mg L\({}^{-1}\)) by the species _Chloella_ sp. in culture flasks in the laboratory. The nitrate and phosphate removals were 38% and 75%, respectively, for kitchen wastewater, and 67% and 88% for sewage wastewater.