RESULTS AND DISCUSSION

Water quality analysis was carried out to assess physico-chemical and biological properties of water at various stages of the treatment and its suitability for domestic and irrigation purposes. Water samples were collected from nine locations (marked in Figure 2) twice at 45 days interval. The water samples were collected in clean acid washed one liter polythene bottles. Temperature, TDS, Conductivity and pH were measured on the site. Water quality parameters were analyzed as per the standard protocol (APHA, 1998). Algal samples collected from sampling locations were identified using standard keys (Prescott 1973;1982) based on their external appearance, colour, morphological characteristics, size, habitat, structure and orientation of chloroplast, cellular structure and pigments etc. Water samples collected were concentrated by centrifuging 15 ml volume.
5.1 Dissolved Oxygen: Dissolved oxygen (DO) is the most essential feature in aquatic system that helps in aquatic respiration as well as detoxification of complex organic and inorganic mater through oxidation. The presence of organic wastes demands high oxygen in the water leading to oxygen depletion with severe impacts on the water ecosystem. The DO of the analyzed water samples varied between 0 to 17.74mg/l. The higher variations of DO especially lower DO values are indicative of high organic matter in the immediate vicinity. The DO was very low at the inlets of wetlands and increased immediately after the algal pond.  Lower DO values were observed near the macrophytes (invasive exotic weeds as water hyacinth, Eichhornia crassipes) infested regions at the outfalls outlets.
5.2 Total Dissolved Solids (TDS):Total dissolved solids present as as mineral matter in the form of dissolved cations and anions and to a smaller extent by organics, sourced from decomposing matter. Other sources include runoff from urban areas, road salts used on street, fertilizers and pesticides used on lawns and farms (APHA, 1998). TDS affect the water quality in many ways impacting the domestic water usage for cleaning, bathing etc as well as drinking purposes (Ramachandra et al., 2012). Surface as well as groundwater with high dissolved solids are of inferior flavor and induce an unfavorable physiological reaction to the dependent population. The TDS values in the samples analyzed, ranged from 612 to 710 mg/lacross all locations. It was higher in the inlets and reduced in the middle region of the lake. The TDS was little higher in the outlets than middle due to human activities (like washing, etc.), macrophyte and plankton cover etc.

Table 1: Onsite parameters

Table 2: Chemical parameters of Water analysis

Table 3: Nutrient analysis of water

5.3 pH: pH is a numerical expression that indicates the degree to which water is acidic or alkaline, with the lower pH value tends to make water corrosive and higher pH has negative impact on skin and eyes. The pH value ranged from 7.2 to 8.4.
5.4 Chlorides:Chlorides are essentially anionic radical that imparts chlorosity to the water. An excess of chlorides leads to the formation of potentially carcinogenic and chloro-organic compounds like chloroform, etc. Chloride values in samples collected from Jakkur lake system ranged from 166-260mg/l. Chloride values were high at inlets (treated and untreated water) and relatively lower at the outlet of algal pond and the middle portion of Jakkur lake. At outlets, it is higher due to washing activities with the use of bleaching powder i.e. CaO(Cl)2.
5.5 Sodium:Sodium (Na) is one of the essential cations that stimulate various physiological processes and functioning of nervous system, excretory system and membrane transport in animals and humans. Increase of sodium ions has a negative impact on blood circulation, nervous coordination, hence affecting the hygiene and health of the nearby localities. In this study the concentration of sodium ranged from 256 to 367 mg/land higher values were observed in samples collected at outlets.
5.6 Potassium:Potassium (K) is an essential element for both plant and animal nutrition, and occurs in ground waters as a result of mineral dissolution, decomposing of plant materials and also from agricultural runoff. Potassium ions in the plant root systems helps in the cation exchange capacity to transfer essential cations like Ca and Mg from the soil systems into the vascular systems in the plants in replacement with the potassium ions (APHA, 1998). Incidence of higher potassium levels in soil system affects the solute transfer (active and passive) through the vascular conducting elements to the different parts of the plants. The potassium content in the water samples ranges between 47-58mg/l. The potassium values were high at outlets due to decomposition of plant materials.
5.7 Alkalinity:Alkalinity is a measure of the buffering capacity of water contributed by the dynamic equilibrium between carbonic acid, bicarbonates and carbonates in water. Sometimes excess of hydroxyl ions, phosphate, and organic acids in water causes alkalinity. High alkalinity imparts bitter taste. The acceptable limit of alkalinity is 200mg/l. Alkalinity of the samples was in range 240-444 mg/l. High alkalinity of 448 and 444 mg/l was observed at the inlet of wetlands (or outlet of the treatment plant). These values declined after the water passed through wetlands (in particular the algal pond) and also in the middle of Jakkur lake.
5.8 Total hardness:Hardness is a measure of dissolved minerals that decides the utility of water for domestic purposes. Hardness is mainly due to the presence of carbonates and bicarbonates i.e temporary hardness and due to sulphates and chlorides i.e. permanent hardness. It is caused by variety of dissolved polyvalent metallic ions predominantly calcium and magnesium cation or other cations like barium, iron, manganese, strontium and zinc. In the present study, the total hardness ranged between 198 to 256mg/l. It was higher in the inlets. High values of hardness are probably due to the regular addition of sewage and detergents.
5.9 Calcium:Calcium (Ca) is one amongst the major macro nutrients which are needed for the growth, development and reproduction in case of both plants and animals. The presence of Ca in water is mainly due to its passage through deposits of limestone, dolomite, gypsum and other gypsiferous materials (APHA, 1998) along with the Ca (from sewage). It contributes to the total hardness of the water. Ca concentration in all samples analyzed periodically ranged between 39 to 71mg/l. Ca concentration was high in the sewage water (treated and untreated) entering into the lake.
5.10 Magnesium:Magnesium (Mg) in one of the most essential macro nutrients that helps as a co-factor in the enzyme systems and in the central metal ions that constitutes the chlorophyll molecule essential for plant photosynthesis. According to WHO guidelines the maximum admissible limit is 50mg/l. In this study the concentration of Magnesium ranged from 19– 26.82 mg/l.
5.11 Nutrients (nitrates and phosphates):Nutrients essentially comprise of various forms of N and P that readily mineralizes (inorganic mineral ions) to enable uptake by microbes and plants. Accumulation of nitrates and inorganic P induces changes in water quality that affects its integrity leading to higher net productivity. Nitrates in excess amounts together with phosphates accelerate aquatic plant growth in surface water causing rapid oxygen depletion or eutrophication in the water. Nitrates at high concentrations (10 mg/l or higher) in surface and groundwater used for human consumption are particularly toxic to young children affecting the oxygen carrying capacity of blood cells (RBC) causing cyanosis (methemoglobinemia). In the present study, nitrate values ranged from 0.2 to 0.38 mg/land phosphate values ranged between 0.09 to 1.29mg/l. The nitrate and phosphate values are higher at the wetlands inlets and significantly reduce after the passage through wetlands and algal pond as elucidated in Figure 4.
5.12 BOD and COD: BOD and COD are important parameters that indicate the presence of organic content. Biochemical oxygen demand (BOD) is the amount of oxygen required by bacteria while stabilizing decomposable organic matter under aerobic conditions. It is required to assess the pollution of surface and ground water where contamination occurred due to disposal of domestic and industrial effluents. Chemical oxygen demand (COD) determines the oxygen required for chemical oxidation of most organic matter and oxidizable inorganic substances with the help of strong chemical oxidant. In conjunction with the BOD, the COD test is helpful in indicating toxic conditions and the presence of biologically resistant organic substances (Sawyer and McCarty 1978). In this study the BOD values ranged from 17-128 mg/l. There was reduction of 66% in BOD after the algal pond and 23% removal in the water which flows out of the lake. The COD values ranged from 16 to 161 mg/l. The COD reduced by 45% in the algae pond and 32 % in the lake as shown in Figure 4.