Soil Salinity and Exchangeable Cations in a Wastewater Irrigated Area, India

Abstract

The salinity and cation composition of water and soil were documented in a large (98 km(2)) wastewater-irrigated area (WIA) downstream of Hyderabad, India. The wastewater, which flows in a river that passes through the city, had a high to very high salinity hazard (EC = 1.1-3.0 dS m(-1)) that increased with distance from the city. The EC of soil irrigated by wastewater sampled within 8 km of the city was 6.2 to 8.4 times the EC of soil irrigated by uncontaminated groundwater. Between 57 to 100% of soil samples in the upper 10 cm within 8 km of the city exceeded the salinity tolerance of rice (Oryza sativa L.). Soil salinity fell rapidly after 8 km downstream and changed most in the upper 0 to 5 cm of the soil, indicating retention of cations in the upper soil horizon. The effect of wastewater irrigation on soil exchangeable cations was most evident for Na(+) (Exch-Na) near the city (<8 km downstream), where Exch-Na averaged 20 to 22 times the Exch-Na in soils irrigated by groundwater outside the WIA. Exchangeable Mg(+) and K(+) correlated with clay percentage, though both still had higher concentrations near the city controlling for clay content. Near the city, where salinity and Exch-Na concentrations were highest, farmers had replaced rice with para grass [Brachiaria mutica (Forsk.)], which has higher salinity tolerance and expanding demand as a fodder crop. Salinity may constrain rice production in wastewater-irrigated areas of India and elsewhere.

Impact of reclaimed water irrigation on soil health in urban green areas

“…Irrigation with reclaimed water has become one of the important alternatives to sustain the existing water resources and enhance current urban water supplies in many cities (Biggs and Jiang, 2009). The conservational benefits of reclaimed water reuse in landscape irrigation are obvious (Anderson, 2003).…”

Natural Water Treatment Systems for Safe and Sustainable Water Supply in the Indian Context: Saph Pani

“…The relatively low TTC counts at the hilly BF sites in Uttarakhand are due to the low population living upstream accompanied by enhanced biodegradation due to the relatively high dissolved oxygen content in the rivers and high river gradient allowing for enhanced aeration of the water. During the non-monsoon period, the turbidity in the river water was found to be below the 5 Nephelometric Turbidity Unit (NTU) drinking water limit (BIS 10500, 2012), except in Srinagar where it was 12 NTU. Under such favourable surface water quality conditions, including extremely low dissolved organic carbon concentrations of mostly ≤1 mg/L, the surface water treatment plants are able to produce potable water conventionally by flocculation, rapid sand filtration and disinfection.…”

“…All sites produce bank filtrate that meets the acceptable limits of most of the general ionic water quality parameters of the Indian Standards (BIS 10500, 2012). An exception is found in Srinagar, where nitrate in the abstracted water from the BF well exceeds the 45 mg/L limit (BIS, 10500, 2012). There the abstracted water is diluted prior to distribution.…”

“…Guideline values for nitrogen species given in the Indian standard (BIS, 10500, 2012) and the WHO drinking water quality guidelines (WHO, 2011) are compared in Table 4.2. The WHO did not establish a guideline value for total ammonia because it usually occurs in drinking water at concentrations well below those of health concern.…”

“…The water quality guidance for MAR (Dillon et al, 2014) refers to a number of existing specifications and guidelines, including the Bureau of Indian Standards (BIS) specifications for drinking water (BIS, 2012) and guidelines for the quality of irrigation water (BIS, 1986). Related guidance is available from Central Pollution Control Board (CPCB) on water quality monitoring protocols (CPCB, 2007) and on well head protection and from BIS on construction of drinking water wells.…”