Assessing the impact of vegetation coverage ratio in a floating water treatment bed of Pistia stratiotes

Kundan Samal,Shivanshi Trivedi,Sudhanshu Upadhyay,Soham Kar

doi:10.1007/s42452-020-04139-2

Abstract

Floating bed (FB) is one of the low cost and efficient system to treat polluted water bodies in rural as well as urban area. It requires less space compared to other macrophyte based treatment system. Vegetation coverage is an effective factor as atmospheric oxygen diffusion to water body depends upon this. When a water body is fully covered by vegetation, it prevents the diffusion of atmospheric oxygen, which is a major source of dissolved oxygen (DO). An optimum vegetation coverage is necessary to obtain maximum treatment efficiency and to verify this a laboratory scale experiment was performed with various vegetation coverage ratio (VCR) of 0, 0.25, 0.5, 0.75, 1. Organics and nutrient removal were measured corresponding to initial floating bed VCR. COD removal for VCR 1.0, 0.75, 0.5, 0.25 and 0 were 86.4%, 93.6%, 96.2%, 85.4% and 60.8%, respectively. The roots of macrophyte (Pistia stratiotes) supports growth of microorganism, which perform biodegradation of organics as well as uptake nutrients. Maximum NH4+-N and PO43−-P removal were observed at VCR of 0.75 and 1.0, respectively. In the tanks with VCR of 0.25, 0.5 and 0.75, the final DO was more than 4 mg/L, which is the requisite DO value for survival of aquatic organism.

Highlights

Rapid urbanization, uncontrolled population growth, climate change and industrial development are the major reasons of high wastewater generation
The discharge from various industries and surface runoff maximize the addition of nutrients, heavy metals, organics and other chemical pollutants to fresh water bodies/lake and transform those to polluted one [1]
Synthetic domestic wastewater was prepared by addition of sucrose, KH2PO4, NaHCO3, NH4Cl, MgSO4, KNO3, CaCl2, MnSO4, H3BO3 in tap water [13]

Summary

Introduction

Rapid urbanization, uncontrolled population growth, climate change and industrial development are the major reasons of high wastewater generation. The discharge from various industries and surface runoff maximize the addition of nutrients, heavy metals, organics and other chemical pollutants to fresh water bodies/lake and transform those to polluted one [1]. Increase in organic content raise the BOD and COD value of water body. Addition of nitrogen and phosphorous from agricultural fields to water body causes eutrophication. Low amount of DO hampers the aquatic life and results in the death of aquatic organisms [2]. Some phytoplankton species like cyanobacteria and blue green algae (BGA) have toxic effect which will be very much harmful if grows in water body. Death of phytoplankton release low molecular weight carbon in the water body which is untreatable by conventional treatment process. Residual carbon helps in regrowth of bacterial species in water distribution system [3]

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Conclusion