Microalgae　are　renewable　and　promising　feedstock　rich　in　biochemicals　for　biofuel　and　bioenergy　production.　The　viability　of　this　technology　relies　on　the　energy-　and　cost-efficient　cultivation　(culture　medium　used)　and　harvesting　(coagulant　applied)　processes.　The　natural　coagulant　of　crystalline　nanocellulose　modified　with　1-(3-aminopropyl)　imidazole　(CNC-APIm)　was　demonstrated　as　a　green　and　recyclable　coagulant　for　microalgal　harvesting.　However,　optimisation　is　still　needed　to　ensure　its　applicability　to　microalgae　cultivated　on　waste-waters,　no　effect　on　biomass　composition,　as　well　as　cost-effective　harvesting.　In　this　study,　microalgal　growth　and　nutrient　removal　capacity　of　Chlorella　vulgaris　(C.　vulgaris)　were　first　investigated　on　two　types　of　municipal　wastewaters.　C.　vulgaris　grew　well　on　both　primary　and　30%　(v/v)　diluted　centrate　wastewaters　with　biomass　productivities　of　0.071　+/-　0.005　and　0.062　+/-　0.006　g/(L.d),　respectively.　High　nitrogen　and　phosphorus　removal　efficiencies　(91.1-100%)　were　obtained.　Subsequently,　the　wastewater-cultivated　C.　vulgaris　was　harvested　using　a　novel　natural　coagulant　of　crystalline　nanocellulose　modified　with　1-(3-aminopropyl)　imidazole　(CNC-APIm).　Based　on　the　optimization　results　of　the　Design　of　Experiments　driven　response　surface　methodology　approach,　the　optimal　conditions　for　maximum　HEs　(86.5%)　and　RCs　(38.5　g-algae/g-CNC)　responses　were　determined　for　C.　vulgaris　under　the　following　conditions:　0.02　g-CNC-APIm/g-algae　of　mass　ratio,　5　s　of　CO2　sparging　time,　8　min　of　air　sparging　time,　and　50　ml/min　of　air　flow　rate.　Moreover,　no　statistically　significant　differences　were　observed　in　the　contents　of　carbohydrate,　protein,　lipid　and　fatty　acids　in　the　biomass　harvested　by　centrifugation　and　CNC-APIm,　respectively,　suggesting　that　CNC-APIm　would　not　impact　the　downstream　microalgal　application.　According　to　the　rough　technical　and　economical　estimation,　CNC-APIm　will　be　an　alternative　to　conventional　coagulants　for　commercial　microalgal　harvesting　application.