Anaerobic-aerobic treatment of purified terephthalic acid (PTA) effluent; a techno-economic alternative to two-stage aerobic process

This paper addresses the treatment of purified terephthalic acid (PTA) effluent using anaerobic and aerobic processes. Laboratory studies were carried out on flow proportionate composite wastewater generated from the manufacturing of PTA. An activated sludge process (ASP-two stage and single stage) and an upflow anaerobic fixed film fixed bed reactor (AFFFBR) were used, individually and in combination. The performance of a full-scale ETP under existing operating conditions was also studied. Full scale ETP studies revealed that the treatment of PTA effluent using a two-stage ASP alone does not meet treated effluent quality within the prescribed Indian Standards. The biomass produced in the two stage ASP was very viscous and fluffy and the sludge volume index (SVI) was very high (200-450 ml/g). However, pretreatment of PTA effluent using an upflow AFFFBR ensured substantial reduction in BOD (63%) and COD (62%) with recovery of biogas at 1.8-1.96 l/l effluent treated at a volumetric loading rate (VLR) 4-5 kg COD/m(3) d. The methane content in the biogas varied between 55% and 60%. The pretreated effluent from the upflow AFFFBR was then treated through a single stage ASP. The biomass produced in the ASP after anaerobic treatment had very good settlability (SVI: 75-90 ml/g) as compared to the two stage ASP and the treated effluent quality with respect to BOD, COD and SS was within the prescribed Indian Standards. The alternative treatment process comprising an upflow AFFFBR and a single stage ASP ensured net power saving of 257 kW and in addition generated 442 kW of power through the AFFFBR.     

Qualitative evaluation of Kanhan river and its tributaries flowing over central Indian plateau

Water quality evaluation of Kanhan river and its tributaries viz. Pench and Nag rivers was carried out in order to assess the qualitative changes and possibility of point and non-point pollution loads in these rivers for the post monsoon and summer seasons. pH, turbidity, conductivity, total alkalinity and total hardness were found in the range 7.18.7, 0.835 (NTU), 227970 (microScm(-1)), 7.18.7, 158486 (mg/L) and 142246 (mg/L), respectively. Ca, Mg, Na and K were in the range 2462, 1328, 15183 and 333 mg/L, respectively. The respective ranges of Cl, SO(4), NO(3) and PO(4) were observed between 19102, 823, 332 and 0.11.4 mg/L. DO and COD in the rivers ranged between nil to 8.5 and 7172 mg/L, respectively. Absence of DO and higher COD in Nag river is due to its sewage content from Nagpur city. Nag river showed higher bacterial counts than Kanhan and Pench rivers. The temporal and spatial variability in the river water quality may be attributed to catchment characteristics, agricultural and urban activities in catchment and on the bank of the river. The values of RSC, ESP and SAR indicated that the water of Kanhan and Pench rivers are suitable, whereas that of Nag river is unsuitable for irrigation purpose.     

Estimation and allocation of solid waste to bin through geographical information systems.

This study presents a geographical information system (GIS)-based procedure for the precise estimation of solid waste generation, computed using the local population density and income group distribution. Using a triangulated irregular network (TIN) in a GIS environment, the procedure further determines the command area for waste allocation to a particular bin which is generally located so the route slopes towards the collection points for ease of transportation by cart pullers. Computational results of bin location, type, size and the frequency of removal are presented for a typical urban area with known population density, income group distribution, road network and topology.     

Impact of climate change on Indian forests: a dynamic vegetation modeling approach

We make an assessment of the impact of projected climate change on forest ecosystems in India. This assessment is based on climate projections of the Regional Climate Model of the Hadley Centre (HadRM3) and the dynamic global vegetation model IBIS for A2 and B2 scenarios. According to the model projections, 39% of forest grids are likely to undergo vegetation type change under the A2 scenario and 34% under the B2 scenario by the end of this century. However, in many forest dominant states such as Chattisgarh, Karnataka and Andhra Pradesh up to 73%, 67% and 62% of forested grids are projected to undergo change. Net Primary Productivity (NPP) is projected to increase by 68.8% and 51.2% under the A2 and B2 scenarios, respectively, and soil organic carbon (SOC) by 37.5% for A2 and 30.2% for B2 scenario. Based on the dynamic global vegetation modeling, we present a forest vulnerability index for India which is based on the observed datasets of forest density, forest biodiversity as well as model predicted vegetation type shift estimates for forested grids. The vulnerability index suggests that upper Himalayas, northern and central parts of Western Ghats and parts of central India are most vulnerable to projected impacts of climate change, while Northeastern forests are more resilient. Thus our study points to the need for developing and implementing adaptation strategies to reduce vulnerability of forests to projected climate change.     

Measuring disaster recovery: bouncing back or reaching the counterfactual state?

How should one measure the recovery of a locale from a disaster? The measurement is crucial from a public policy and administration standpoint to determine which places should receive disaster assistance, and it affects the performance evaluation of disaster recovery programmes. This paper compares two approaches to measuring recovery: (i) bouncing back to pre‐disaster conditions; and (ii) attaining the counterfactual state. The former centres on returning to normalcy following disaster‐induced losses, whereas the latter focuses on attaining the state, using quasi‐experimental design, which would have existed if the disaster had not occurred. Both are employed here to assess two housing recovery indicators (total new units and their valuations) in Hurricane Katrina‐affected counties (rural and urban). The examination reveals significantly different outcomes for the two approaches: counties have not returned to their pre‐disaster housing conditions, but they do exhibit counterfactual recovery. Moreover, rural counties may not be as vulnerable as assumed in the disaster recovery literature.     

Measurement of natural radioactivity in chemical fertilizer and agricultural soil: evidence of high alpha activity

People are exposed to ionizing radiation from the radionuclides that are present in different types of natural sources, of which phosphate fertilizer is one of the most important sources. Radionuclides in phosphate fertilizer belonging to ²³²Th and ²³⁸U series as well as radioisotope of potassium (⁴⁰K) are the major contributors of outdoor terrestrial natural radiation. The study of alpha activity in fertilizers, which is the first ever in West Bengal, has been performed in order to determine the effect of the use of phosphate fertilizers on human health. The data have been compared with the alpha activity of different types of chemical fertilizers. The measurement of alpha activity in surface soil samples collected from the cultivated land was also performed. The sampling sites were randomly selected in the cultivated land in the Midnapore district, which is the largest district in West Bengal. The phosphate fertilizer is widely used for large agricultural production, mainly potatoes. The alpha activities have been measured using solid-state nuclear track detectors (SSNTD), a very sensitive detector for alpha particles. The results show that alpha activity of those fertilizer and soil samples varies from 141 Bq/kg to 2,589 Bq/kg and from 109 Bq/kg to 660 Bq/kg, respectively. These results were used to estimate environmental radiation exposure on human health contributed by the direct application of fertilizers.     

Simulation of impact of oil spill in the ocean – a case study of Arabian Gulf

To meet the growing energy demand worldwide, oil and gas exploration and production activities have increased rapidly both in onshore and offshore areas. The produced oil from the ocean bed is transported onshore either by ship or pipeline. This has increased the risk of oil spill in the coastal area. In order to prepare an emergency preparedness plan and to assess the magnitude of risk involved in transporting and offloading oil, oil spill simulation studies play an important role. This paper describes a simulation of oil spill in coastal bay of Arabian Gulf where new developments are taking place using MIKE 21 model. The developments include a diesel based thermal power plant near Sir Baniyas Island, which is an ecological fragile area. Based on the project activity, two probable scenarios, one for diesel leak (250 m3/h) for 1 h and the other for instantaneous spill (500 m3) are considered. The MIKE 21 model was calibrated for hydrodynamics using measured field data followed by diesel-spill simulation to track its movement in the Arabian Gulf. The results for both leak and instantaneous spill indicate that spilled diesel will not move towards the Sir Banyas Island and more than 45% of the diesel will be evaporated within 48 h of oil spill. Based on the results, a clean up and contingency plan is proposed to mitigate the adverse impacts arising due to diesel spill in the study area.