Understanding the Deteriorating Condition of Hussain Sagar Lake
Lakes are primary sources of water for domestic and industrial purposes worldwide. They also serve as infiltration sources for groundwater and recharging the aquifers. Due to rapid industrialization and population growth, the demand for clean water has also increased. Many natural water bodies are being polluted due to the dumping of untreated hazardous waste from industries and domestic households. Domestic sewage poses health-related issues, while industrial effluents carry a wide variety of toxic elements like Cd, Cr, Pb, Hg, and Zn, which can cause significant toxicity even in trace amounts.
Hussain Sagar Lake – once the primary source of water in Hyderabad, India, has become one of the most polluted lakes over the past few years due to the continuous discharge of untreated toxic effluents from nearby industries. Water quality monitoring of the lake is required to understand its characteristics and assess the current situation. In this study, we analyzed the lake water characteristics, existing cleaning methods implemented by authorities, and provided recommendations for restoration and management of the lake.
The water samples were collected from four different locations to test the water quality parameters. The results show that the concentration of total solids is 4300 mg/l, which is four times higher than the maximum suggested limit. Alkalinity (875 mg/l) and turbidity (134 NTU) are very high, indicating the high concentration of wastewater. The dissolved oxygen is nearly zero – posing a threat to aquatic life, and the Biochemical Oxygen Demand (BOD) is 105 mg/l, much higher than the acceptable limits.
In conclusion, the water quality in the Hussain Sagar lake is significantly degraded and demands immediate attention. We recommend undertaking a performance evaluation of its existing treatment facilities to analyze their efficiency. Construction of a new sewage treatment plant, implementation of wetland method, rapid sand filtration, and floating treatment methods can aid the restoration of the lake.
Assessing the Impact of Industrial Effluents on Urban Water Bodies
Urban areas with dense populations and high water demands require effective management of water resources for sustainable development. This includes optimizing water usage and recycling wastewater to balance supply and demand. Urban rivers, which now carry sewage year-round due to increased urban water consumption, are increasingly used for irrigation in peri-urban regions.
This study aims to assess the suitability of an urban stream for irrigation compared to catchment groundwater, using hydrochemical parameters to evaluate water quality indices. Analysis of major ion distribution from upstream to downstream reveals a significant increase of TDS (r^2 = 0.65; p < 0.001), with the order of cations Ca^2+ > Mg^2+ > K+ and anions HCO3- > Cl- > SO4^2- > NO3- > CO3^2- > PO4^3- > F- in decreasing concentration.
In the case of groundwater samples, the concentration of cations Na+ > Ca^2+ > Mg^2+ > K+ and the anions Cl- > HCO3- > SO4^2- > NO3- > CO3^2- > F- follow a typical trend along the Musi river. The high concentrations of major ions are noticed in the Musi catchment in comparison to the surface water chemistry of peninsular rivers, attributed to wastewater discharge from industrial and pharmaceutical sources.
The calculated wastewater fraction (Fw) in the surface water and groundwater samples varied from 0 to 0.82 and 0 to 0.38, respectively. The urban stretch region witnessed the highest Fw values, mainly in surface water samples, further validating that the anthropogenic municipal waste discharge is the major source of contamination in the Musi river.
Evaluating Irrigation Suitability of Polluted Urban Water
The wastewater fraction (Fw) and ionic deltas (ΔNa+, ΔCa^2+, ΔMg^2+, ΔHCO3-, ΔPO4^3-, ΔK+ and ΔNO3-) were plotted to assess the impact of wastewater on surface water and groundwater quality. The distribution of scatter plots indicates that except K+, all major ions show positive ionic delta values. Spatially, the upstream region displays negative ionic delta values, suggesting minimal wastewater influence. In contrast, the midstream region exhibits enriched major ion concentrations due to wastewater contribution in both surface water and groundwater samples.
Pearson correlation analysis revealed significant (p < 0.01) positive correlations between major ions, indicating the influence of wastewater on water quality. The Kelly’s ratio, a widely used irrigation suitability index, varies from 0.2 to 2.1 (average: 1.2) and 0.1 to 4.0 (average: 0.9) in surface water and groundwater, respectively. Only 16% of the surface water samples are suitable for irrigation, while 60% of the groundwater samples are suitable.
The spatial pattern of nitrogen, phosphate, and potassium ions in the surface and groundwater samples shows a clear increase of NO3–N concentrations in the midstream and downstream regions. The mean value of NO3- in the midstream (114 mg/l) is double that of the upstream (43 mg/l) and downstream (45 mg/l) regions, indicating that the urban stretch is the major source of nitrate. In the case of groundwater, a clear source-to-sink increase of NO3–N is noticed, with the mean value four times higher than the surface water in the downstream region.
The NPK ratios across the basin are exceptionally higher than the recommended levels for crop cultivation, suggesting that crops irrigated using the Musi water might not require additional fertilizer applications. However, the excess NPK in the supplied water can still lead to the accumulation of nitrate in groundwater, posing environmental and health concerns.
Recommendations for Sustainable Water Management
The downstream utilization of treated river water and groundwater for irrigation purposes needs special attention, as the reuse of this water might alleviate water scarcity and provide essential nutrients to crops. However, the environmental and human health consequences of heavy metals, organic pollutants, and pathogens in partially treated urban wastewater remain unknown.
This study emphasizes the need for a comprehensive assessment of irrigation suitability for wastewater reuse, focusing on chemical and microbiological parameters through integrated water quality modeling and risk assessment frameworks. Additionally, the development of holistic policies that balance wastewater reuse with environmental protection and public health is crucial for achieving sustainable agriculture in regions like the Musi river basin.
The city’s municipal administration must immediately ramp up sewage treatment facilities to ensure that the sewage water leaving the city boundaries and used for irrigation downstream is adequately treated. The use of synthetic fertilizers should also be regulated to achieve sustainable agricultural growth and safeguard public health.
Further studies are required to estimate the bioaccumulation of trace elements, heavy metals, organic pollutants, and pathogens to suggest switching to commercial non-food crops. Strategic policies and guidelines that balance wastewater reuse, environmental protection, and public health must be developed for achieving sustainable agriculture in the downstream regions of urban rivers.
