Baja Serbajadi Humus 27 (organic fertilizer or compost) with
granular shape was purchased from a local market. A 10 g of the
fertilizer was immersed in 600 mL tap water and stirred for 24 h
using magnetic stirrer. Non-soluble particulate solids were
observed after the stirring process and were filtered using filter
paper (Double Rings 101). The resulting organic fertilizer medium
was dark-brown in colour with typical characteristics as shown in
Table 1. From the Table, the concentrated organic medium contains
two types of nutrients which are equally important to support microalgae
growth: (1) macronutrients, such as nitrogen, phosphorus,
potassium, calcium and magnesium and (2) micronutrients, such
as manganese, boron and iron. In addition, the prepared medium
also contains exceptional high level of Chemical Oxygen Demand
(COD) and Biochemical Oxygen Demand (BOD), in which those values
are similar to untreated wastewater [24]. On the other hand,
the filtered particulate solids (organic compost) can be further
used as soil amendment to increase the water and nutrients holding
capacity and to improve soil physical properties by providing
better aeration [25].