Abstract:
A high level of water hardness in drinking water is a serious problem in different regions
of Sri Lanka. Phytoremediation acts as an effective, environmentally friendly, and lowcost technology for the removal of water hardness. Therefore, the current study was
intended to identify the potential usage of Hygrophila schulli (Neeramulliya) for the
removal of water hardness using a hydroponic system. This plant was selected for the
current study based on traditional beliefs, literature records, and availability in the natural
environment. Preliminary trials were conducted to identify the appropriate maturity stage
of plants, the number of plants, treatment time, and growth medium of hydroponic
system. Based on the above results, final experiments were conducted in two hydroponic
systems (Treatment 01: 4 plants, Treatment 02: 5 plants) with 16 L of natural hard water
(Initial hardness: 300 mg L-1 CaCO3) in the growth medium of 1:1 ratio of coconut coir:
sand using one-month-old H. schulli plants. Three replicates for each of the systems were
used during the final experiment. Temperature, pH, Electrical Conductivity, Dissolved
Oxygen, and Hardness level of water were measured every 12 hours for 36 hours of the
experimental period. According to the results, the number of plants and treatment time
had a significant effect on the removal rate of water hardness (p<0.05). The hardness
removal efficiency of 2 treatment systems ranges at an average of 3.85-21.25% within 36
hours. This explains the capacity of H. schulli plants in absorbing causative ions
responsible for water hardness during the phytoremediation process. The hydroponic
system with 5 plants per unit was recorded average 250 mg L-1 of hardness which satisfies
the standard level permissible for drinking water after 36 hours of the time. Accordingly,
the absorbance level of Ca2+ ions had recorded 10 mg L-1 per single plant of H. schulli.
Consequently, the treatment system having 5 plants acts as the most effective hydroponic
unit in the removal of water hardness. There was no significant difference between pH,
Dissolved Oxygen, Electrical Conductivity level in each experimental system, and
treatment time (p>0.05). The current study recommends identifying the applicability of
similar hydroponic units for removal of extremely high hardness levels from natural water
which is over 500 mg L-1
in certain areas of Sri Lanka. In conclusion, this study reveals
the appropriateness of H. schulli for the reduction of hardness level (300 mg L-1 CaCO3)
during the water treatment process.
Keywords: Hardness Removal Rate, Phytoremediation, Hydroponic system, Water
quality parameters, Water treatment
