Floating Constructed Wetlands Efficiency in Removal of Total Hardness, Calcium and Magnesium from Secondary Treated Sewage Water

Abstract

Floating Constructed wetlands (FCWs) also popular as Floating Treatment Wetlands (FTWs) were used in situ for suspended solids,heavy metals, biological oxygen demand (BOD), chemical oxygen demand (COD), faecal coliform bacteria, nutrients and heavy metalsremediation from various types of wastewater. However, there was limited data available on total hardness (TH), calcium (Ca2+) andmagnesium (Mg2+) ions removal from secondary treated sewage water (STSW). This article focuses on TH, Ca2+ and Mg2+ ions removalefficiency of FCWs from STSW. Mesocosms include a control (without FCWs), FCWs planted with macrophyte plant species Cannaindica var. indica L. (S1) and Typha angustifolia L. (S2) and one mixed culture with both Typha and Canna plants (S3). The changes in TH,Ca2+ and Mg2+ concentration in wastewater were recorded at a 7-day hydraulic retention time (HRT) for 7 batches. Mean percentageremoval efficiency recorded was 9.8, 1.7, 4.9 and 11.2% for TH, -3.4, 7.6, 27.1 and 14.1% for Ca2+and 29.5, 4.2, -0.6, and -0.6% for Mg2+,in Control, S1, S2, S3 FCWs respectively. Results showed that S2 and S3 FCWs are effective in TH and Ca2+ removal but not for Mg2+ ions.Thus, FCWs can reduce TH and Ca2+ ions concentration along with nutrients from STSW.