A Better World - Volume 3: Ensure Access to Water and Sanitation for All

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Constructed wetland for the treatment of industrial effluent

A small CW was commissioned at the Sangareddy campus of

SAB Miller, a large brewery, to investigate the bioremediation

potential of industrial wastewater. The CW comprised two

chambers; a 20m x 20m x 1m sub-surface cell and a holding

tank of the same capacity for the treated wastewater. The sub-

surface cell featured a 250mm-deep layer of 40mm-diameter

gravel at the bottom, covered with two successive layers of

medium (20mm) and small (10mm) gravel, each to a depth

of 250mm. A 150mm layer of 1.5mm coarse sand constituted

the top layer. The CW was sown with

Cana indica

during

November 2015 and the plants were established by January

2016. The hydraulic loading rate was 60m

/day and the CW

operated with a hydraulic retention time of approximately

three days. The average wastewater treatment efficiency of

the wetland is given in Table 2. The pH value of the wastewa-

ter remained in the alkaline range throughout the trial, both

at the inlet and the outlet of the CW. The chemical oxygen

demand (COD) as well as the inorganic nitrogen removal

efficiency (RE) were 78% and 85% respectively. The treated

wastewater COD of 21mg/L was much less than the limit of

250mg/L prescribed by the Central Pollution Control Board

of India (CPCB, India) for irrigation suitability. The phos-

phate removal efficiency was 37.8 %.

The high salt concentration was reflected in the electrical

conductivity reading of above 2ms/cm for both the inlet and

outlet (the 2010 CPCB irrigation standard is set below 4 ms/

cm). The overall sodium absorption ratio (SAR) indicated

little change between inlet and outlet but fell well short of

the 2009 CPCB standards which sets the SAR limit at 26. The

treated wastewater had 166mg/L chloride which is less than

the The Food and Agriculture Organization of the United

Nations standard of 354mg/L. However, alkalinity – the

measure of dissolved carbonates, bicarbonates, and hydrox-

ides concentration – in the wastewater was much greater than

the desirable 100mg/L limit for agriculture. The combination

of high alkalinity and high pH therefore reduced the poten-

tial of use for irrigation of the treated wastewater. The treated

wastewater was subsequently used for sugar cane cultivation

in the adjacent black soil fields with a yield of 43t per acre.

Constructed wetland sown with

Cana indica

at SAB Miller, Sangareddy,

Telangana, India. Top: November 2015; bottom: January 2016

Phases of sugarcane cultivation at SAB Miller, Sangareddy, Telengana,

India, showing: planting; cane sprouting; 38 days after planting;

90 days after planting

Images: ICRISAT