Pak. J. Bot., 46(3): 1011-1018, 2014. EVALUATION OF WASTE STABILIZATION PONDS EFFLUENT EFFICIENCY ON THE GROWTH AND NUTRITIVE CHARACTERISTICS OF CLUSTER BEANS (CYAMOPSIS TETRAGONOLOBA L.) TAUB. MOAZZAM ALI KHAN * , S. SHAHID SHAUKAT, AAMIR ALAMGIR AND SYED ADNAN HASAN Institute of Environmental Studies, University of Karachi, Karachi-75270, Pakistan Corresponding author e-mail: sherwanis@hotmail.com Abstract South Asian countries including Pakistan are facing chronic shortage of water supply which is anticipated to be aggravated in future. These countries are agribased where the continued water supply is crucial for sustainable economy. One of the possible alternatives to overcome the problems of water scarcity is the used of treated wastewater which is gaining much importance even in the western world. The treated wastewater can be used as a liquid fertilizer which could provide dual benefits both in terms of saving of fresh water as well as inorganic fertilizers. The potential of treated effluent from waste stabilization ponds (WSP) and equivalent basal fertilizer on growth and nutritive quality of cluster beans (Cyamopsis tetragonoloba L.) Taub. was investigated under field conditions. Treated effluent significantly increased fresh weight of leaves and stems. Dry weight of stem was also significantly higher with the treatment of WSP effluent as compared to the use of basal fertilizer and fresh water. Fresh and dry fruit weights, number of seeds per fruit and fruit length were also significantly increased in WSP effluent treatment as compared to other two treatments. Treatment with WSP effluent also improved the nutritive characteristics such as crude proteins and total carbohydrates. However, total fat and ash content percentage of Cyamopsis tetragonoloba remained unaltered. The application of WSP effluent also increased NPK and organic matter content of the soil after harvesting the crop which would be helpful for succeeding crop. The study demonstrated that treated effluent can be successfully used for unrestricted irrigation in the water deficient areas of Pakistan thereby saving huge quantities of fresh water. Introduction Fresh water scarcity is a common problem in countries like Pakistan which are situated in arid and semi arid regions of the world. Water scarcity problem in Pakistan is quite alarming in the face of agri-based economy of the country. One alternative to overcome the acute shortage of water supply is the use of treated wastewater for unrestricted irrigation (Aghtape et al., 2011; Oron et al., 2007; Mohammad & Mazahreh, 2003; Al-Rashed & Sherif, 2000; Vazquez-Montiel et al., 1996; Al-Jaloud et al., 1995; Feigin et al., 1991; Bouwer & Idelovitch, 1987). The major limitation pertaining to the use of treated wastewater is its effective management and treatment to protect public health at an affordable cost (Sipala et al., 2003; Anderson et al., 2001; Agunwamba, 2001; Asano & Levine, 1996; Marcos do Monte et al., 1996; Asano et al., 1992). The developing countries which cannot afford sophisticated biomechanical systems of wastewater treatment are exploiting waste stabilization ponds (WSP) technology for both restricted and unrestricted irrigation (Khan et al., 2010, Khan et al., 2009, Khan et al., 2008; Khan & Khan, 2007; Alcalde et al., 2003, Mara & Pearson, 1998). The technology provides low operation and maintenance cost with effective removal of pathogens which has made WSP technology as a treatment of choice in many parts of the world specially in tropical and subtropical regions (Alcalde et al., 2003; Mara & Pearson 1998; Khan & Ahmed, 1992; Mara, 1987). In Pakistan scientific work on WSP technology is very scanty, and the commercial exploitation has not been initiated so far through which the treated wastewater can be converted into economic asset rather than an economic burden (Khan et al., 2010; Khan et al., 2009; Khan et al., 2008; Khan & Khan, 2007). Cluster bean (Cyamopsis tetragonoloba L.), locally known as Guar, is a drought resistant annual crop grown in semiarid region. In Pakistan it is usually cultivated in May-June and harvested in August- September. It is used as a common vegetable in Pakistan where it is considered as summer delicacy. The crop is also used for the production of guar gum for which Pakistan is also one of the major world suppliers (Shaukat et al., 2010) through which the country earns huge foreign exchange (Vahidy & Yousuf Zai 1991). Cyamopsis tetragonoloba is also used as green manure owing to its high C/N ratio (Hussain et al., 1995). It increases the amount of nitrogen in soil (Gurusaravanan et al., 2012) besides altering a number of soil characteristics. It is well known that microbial biomass is a sensitive index of tillage and crop- induced changes in the biological characteristics of soils (Mele & Carter, 1995). Ashraf et al., (2002) reported that it can also be cultivated in hyper saline soil because of its inherent genetic potential. The present study was designed to explore the potential of treated effluent from Waste Stabilization Ponds (WSP) for the growth of Cyamopsis tetragonoloba. The study demonstrated that the effluent can be efficiently used for the commercial production of Cyamopsis tetragonoloba even in the areas where droughts cause frequent failure of many other crops. The use of treated effluent not only improves the characteristics of soil but also enhances the microbial biomass. Materials and Methods Technical details of ponds: The two waste stabilization ponds used in the present study are available at Karachi University Campus that were constructed in consultation with the Institute of Environmental Studies, University of Karachi. The technical details are given in Table 1.