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A process for the production of biogas through the anaerobic digestion (AD) of date palm tree waste (DPTW) was developed. The effects of different substrate pretreatments and operating conditions on the yield of biogas and on the chemical composition of DPTW before and after AD were studied. The best results were obtained using alkali pretreatment, with a particle size of 2 to 5 mm, a C:N ratio of 30:1, a digestion temperature of 40 °C, an initial pH of 7.0, and a volatile solids concentration of approximately 10%. The production of flammable biogas containing up to 50% methane started after about one week of operation and continued for approximately 11 weeks. The highest average biogas yield obtained was 342.2 L gas/kg of volatile solids fed to the digester. The highest maximum and average volumetric biogas production rates obtained were 674.5 and 404.4 L/m3 of digester volume per day, respectively. After digestion, there was up to a 58% reduction in the organic matter content of the substrate. Reductions in the contents of cellulose, hemicellulose, and soluble organic compounds were 68.7, 73.4, and 71.9%, respectively, while the ash and lignin contents remained mostly constant. The remaining sludge contained nutrient minerals and some organic matter which qualifies it as a potential soil fertilizer for crop production.

Chains of accidents (the domino effect) have been occurring with ever increasing frequency in chemical process industries. This is reflected in several accidents ‘J Loss Prevent Process Ind 12 (1999a) 361’; the world's worst industrial accident of the 1990s — the Vishakhpatnam disaster — also involved the domino effect ‘J Loss Prevent Process Ind 12 (1999a) 361; and Process Safety Prog 18 (1999b) 135’. Such chains of accidents have a greater propensity to cause damage than stand-alone accidents ‘Process Safety Prog 17(2) (1998a) 107; and J Loss Prevent Process Ind 12 (1999a) 361’. In order to assess the likelihood of occurrence of the domino effect and its damage potential, use of deterministic models in conjunction with probabilistic analysis is required. Recently we have proposed a systematic methodology called ‘domino effect analysis’ (DEA). A computer-automated tool, DOMIFFECT, has also been developed by us based on DEA ‘Process Safety Prog 17(2) (1998a) 107; Environment Model Software 13 (1998b) 163; and Risk assessment in chemical process industries: advanced techniques. Discovery Publishing House (1998c)’. This paper illustrates the application of DEA and DOMIFFECT to an industrial complex comprising 16 different industries. Out of 12 credible accident scenarios envisaged in three different industries — namely Madras Refineries Limited (MRL), UB Petrochemicals (UBP) and Indian Organic Chemicals Limited (IOCL), eight scenarios are likely to cause the domino effect. A further detailed analysis reveals that accidents in the storage of liquified petroleum gas and propylene and in the reflux drum units of MRL may cause domino effects. Similarly, propylene storage of UBP and monoethylene glycol storage of IOCL are also likely to cause domino effects. The impact of various chains of accidents has been forecast which reveals that in several cases the accidents may be catastrophic, harming the entire industrial complex of 16 industries. The study leads to the identification of ‘hot spots’ — units that pose the greatest risk — in turn forewarning the industries concerned and enabling them to prioritize and augment accident-prevention steps.

The viability of vermireactors fed with different proportions of water hyacinth (WH) and cowdung (CD) was assessed over six-month trials. All reactors performed sustainably with a steadily rising vermicast output, worm zoomass, and number of offspring. There was no mortality in any of the reactors. A change in the WH:CD ratios from 4:1 to 6:1 had no discernable impact on the reactor performances. Attempts were also made to improve the efficiency of the reactors in terms of vermicast production per unit time and per unit digester volume. These attempts led to the 'high-rate' vermireactor in which 5.6 times greater vermicast was produced per litre of digester volume per day than in the 'low-rate' reactors. The high-rate vermireactors also performed sustainably, with steady vermicast output, animal growth, and reproduction.

A computer-automated tool TORAP, developed recently by us, has been applied to conduct an illustrative risk assessment of a typical fertilizer plant. Hazardous units have been identified and elaborate scenarios have been generated of the accidents likely in these units. The consequences of the accidents, in terms of the damage to life and property that they may cause directly as well as the likelihood of causing secondary and higher-order accidents (domino effect), have also been studied. Apart from demonstrating the applicability of TORAP, these studies reveal the nature and size of several major hazards existing in a typical fertilizer plant. The studies also, indirectly, highlight the lack of seriousness with which such hazards are normally perceived, and emphasize the need for a thorough reassessment of the risk posed by such industries.

Paper waste, spiked with varying proportions of cowdung, was vermicomposted in `low-rate' and `high-rate' reactors. The former type of reactors had earthworm populations and feed loading rates similar to ones recommended by previous workers. The `high-rate' reactors were operated with 12.5 times higher earthworm densities and feed loading rates. All the reactors were studied for six months to assess the vermicast output, survivability, growth and reproduction of the earthworms – hence the sustainability of the reactors – for long-term, continuous operation. The studies revealed the viability of the high-rate vermireactor concept. The high-rate reactors consistently produced over 6.5 times more castings per unit digester volume with no adverse effect on the earthworm population, as reflected by (a) absence of mortality, (b) consistent growth in worm zoomass, and (c) normal rate of reproduction. The studies also revealed that an increase in the cowdung fraction in the feed from 14.3% to 20% (4:1 paper:cowdung blends to 6:1 blends) had little positive impact on the vermicast output or earthworm health. This indicated that spiking of paper feed with ∼14% cowdung, or perhaps an even smaller fraction, might be adequate to support earthworms in the paper-fed vermireactors.

In the context of risk assessment and loss prevention in chemical process industries, the term domino effect denotes ‘chain of accidents’, or situations when a fire/explosion/missile/toxic load generated by an accident in one unit in an industry causes secondary and higher order accidents in other units. Most of the past risk assessment studies deal with accident in a single industry, more so in one of the units of an industry. But, often, accident in one unit can cause a secondary accident in a nearby unit, which in turn may trigger a tertiary accident, and so on. The probability of occurrence and adverse impacts of such ‘domino’ or ‘cascading’ effects are increasing due to increasing congestion in industrial complexes and increasing density of human population around such complexes. The multi-accident catastrophe which occurred in a refinery at Vishakhapatnam, India, on 14 September 1997, claiming 60 lives and causing loss of property worth over Rs 600 million, is the most recent example of the damage potential of domino effect [Lees F.P. Loss prevention in process industries, 2nd ed. Butterworths, 1-3, London; Khan, F.I., & Abbasi, S.A. (1999a). Major accidents in process industries and an analysis of their causes and consequences. Journal of Loss Prevention in Process Industries, 12, 361–378; Khan, F.I., & Abbasi, S.A. (1999b). The worst chemical industry accident of 1990's–what happened and what might have been: A quantitative study. Process Safety Progress, 18, 135–145]. Recently, we have proposed a systematic methodology called ‘domino effect analysis’ (DEA). A computer automated tool DOMIFFECT has also been developed by us based on DEA [Khan, F.I., & Abbasi, S.A. (1998a). Models for domino effect analysis in chemical process industries. Process Safety Progress — AIChE, 17 (2), 107–113; Khan, F.I., & Abbasi, S.A. (1998b). DOMIFFECT (DOMIno eFFECT): a new software for domino effect analysis in chemical process industries. Environmental Modelling and Software, 13, 163–177.]. The methodology is based on deterministic models used in conjunction with probabilistic analysis. This paper illustrates the application of DEA and DOMIFFECT to an industrial complex. Out of 16 credible accident scenarios envisaged in four closely situated industries namely Madras Fertilisers Limited (MFL), SPIC–Heavy Chemical Division (SPIC–HCD). Manali Petrochemical Limited (MPL), and Tamilnadu Petroproducts Limited (TPL), ten scenarios forecast domino effect. Further analysis reveals that accidents in the ammonia synthesis unit, secondary reformer, and urea reactor of MFL may cause domino effect. Similarly, accidents in the storage units of propylene oxide, ethylene oxide and mono propylene glycol at MPL, hydrogen storage units at SPIC–HCD, and the propylene oxide and fuel oil storage units of TPL are likely to cause a domino effect. The consequences of all these credible accidents have also been forecast. The paper makes a strong case for making DEA an integral part of all risk assessment initiatives.

Four specices of detritivorous (humus-former) earthworms were tested for their ability to vermicompost paper waste blended with cowdung in 6:1 (w/w) ratio. The anecic Lampito mauritii, Kinberg and the epigeic Eudrilus eugeniae, Kinberg were the most effective of the four species employed; 20 animals of each of these species generated castings amounting to about 52% of the feed mass (75 g) per fortnight. The performance of these two species was followed by the anecic Drawida willsi, Michaelsen and the epigeic Perionyx excavatus, Perrier; they achieved approximately 46% vermiconversion in comparable settings. The vermireactors were sustainable as the animals have remained consistently healthy and reproductive over a period of six months, and are continuing to remain so, turning in a steadily rising vermicast output. During this period E. eugeniae have grown to 2.3 times their original weight while the other three species have more than trebled their weights. The studies establish the feasibility of vermicomposting as a viable process for the gainful utilization of paper waste in an environmentally clean manner. They also indicate that all the four species of the worms screened by us are suitable for the process, with L. mauritii and E. eugeniae a shade more efficient than the other two species.

Risk assessment is an essential prelude to the development of accident prevention strategies in any chemical process industry. But, the high costs and time involved in conducting risk assessment by conventional techniques often becomes a deterrent. In order to circumvent this problem, the authors have developed a risk analysis methodology based on a set of reliable rapid techniques and tools. The suitability of the methodology, named by us ORA (Optimal Risk Analysis), has been demonstrated by applying it to a real-life situation.

Trees, shrubs, and other vegetation can absorb and assimilate certain air pollutants if the pollutants are present within tolerable levels. This concept is being increasingly used in developing strips of vegetation, often called ‘greenbelts’ around sources of pollution. But several intricacies are associated with the exercise of effective and optimal designing of greenbelts. The pattern of dispersion of air pollutants, as effected by the density of the gaseous plume and the meteorology of the area, must be studied with great precision because these aspects would determine the location and the geometry of the greenbelt. The species composition in the greenbelt should confirm to the pollutants to be attenuated as to the geoclimatic conditions of the region. Decisions on the tree heights, and the sequence of plantation of trees and other vegetation also similarly require complex inputs. In this paper, the authors have addressed these issues and have presented a set of mathematical models, which may help in the rational and optimal design of greenbelts.

There is, as yet, no proven methodology to enable, objectively,the identification of key parameters out of a large number one normally encounters during any EIA. As EIA is a costly and time-consuming exercise, it is necessary to separate the man from the boys – so to speak – in order to optimize costs andefforts.In this paper a methodology for distinguishing the moreimportant parameters from the less important ones, developed byus, is described. The methodology aims at identifying andshortlisting the key parameters which ought to be studied in agiven EIA situation, thereby helping in reducing time, effort,and cost of EIA. With this methodology a system structure is developed whichgives hierarchical pattern of inter-parameter interaction, andreveals several distinguishing features of each parameter. Asoftware package INTRA (INTer-parameter Relationship Analysis)based on this methodology, has been developed. The paper alsodescribes a case study in which INTRA has been used to study theenvironmental impacts of urbanization of a typical third worldtown (Roorkee).

This paper presents a risk assessment study of a typical chemical process (sulfolane manufacturing) industry using optimum risk analysis (ORA) methodology recently proposed by these authors ( Khan, F. I., & Abbasi, S. A. (1995) . Risk analysis; a systematic method for harzard identification and assessment. Journal of Industrial Pollution Control, 9(2), 66; Khan, F. I., & Abbasi, S. A. (1998a). Techniques for risk analysis of chemical process industries. Journal of Loss Prevention in Process Industries, 11(2), 91.) The paper also describes briefly the different steps of ORA methodology and the available techniques and tools to conduct each step of the ORA. The study suggests that the reactor and the storage units of the industry are highly vulnerable to accidents and need elaborate safety arrangements. The damage potential of these units is such that its impact would permeate far beyond the plant boundaries and would cause damage to nearby areas. A few recommendations have been made to reduce the existing risk potential. However, the industry still needs to have high level safety arrangements and emergency procedures in position to counter any unwanted situation in the industry.

Fault tree analysis (FTA) is based on constructing a hypothetical tree of base events (initiating events) branching into numerous other sub-events, propagating the fault and eventually leading to the top event (accident). It has been a powerful technique used traditionally in identifying hazards in nuclear installations and power industries. As the systematic articulation of the fault tree is associated with assigning probabilities to each fault, the exercise is also sometimes called probabilistic risk assessment. But powerful as this technique is, it is also very cumbersome and costly, limiting its area of application. We have developed a new algorithm based on analytical simulation (named as AS-II), which makes the application of FTA simpler, quicker, and cheaper; thus opening up the possibility of its wider use in risk assessment in chemical process industries. Based on the methodology we have developed a computer-automated tool. The details are presented in this paper.

Anaerobic digestion is one of the major steps involved in the treatment of dairy industry waste-waters and many CSTRs (continuously-stirred tank reactors) are functioning for this purpose all over the world. In this paper, the authors describe their attempts to upgrade a CSTR's performance by incorporating a biofilm support system (BSS) within the existing reactor. The focus of the work was to find an inexpensive and easy to install BSS which could significantly enhance the rates of waste treatment and methane recovery. Rolls of nylon mesh (with ∼1 mm openings), of 5 cm height and 2 cm dia, when incorporated in the CSTR at the biofilm surface (with a digester volume ratio 0.3 cm2/cm3), enabled the CSTR to perform better with > 20% improvement in the methane yield. Such simple BSS devices can significantly improve the performance of a CSTR anaerobic digester treating dairy wastes. The enhancement is due to the development of active biofilms which not only enhance the microorganism-waste contact but also reduce the microbial washout. Such devices are inexpensive and very easy to incorporate — the gains are thus achieved with very little cost and effort.

The use of a new computer-automated tool TORAP (TOol for Rapid risk Assessment in Petroleum refinery and Petrochemical industries) is demonstrated through a rapid and quantitative risk assessment of a typical petroleum refinery. The package has been applied for an appraisal of the risks of accidents (fires, explosions and toxic release) posed by different units of the refinery, and to identify steps to prevent/manage accidents. The studies reveal that TORAP enables a user to quickly focus on the accidents likely to occur, and enables forecasting the nature and impacts of such accidents. This information is directly utilizable in identifying 'soft' spots and in taking appropriate remedial measures to prevent or control accidents. The special attributes of TORAP are: (a) wide range of applications — achieved by incorporating models capable of handling all types of industrial fires and explosions, (b) sophistication — brought about by including state-of-the-art models developed by these authors and others, (c) user-friendliness — achieved by incorporating on-line help, graphics, carefully formatted output, and, above all, an automatic module, with which even a lay user can conduct a risk assessment. The entire package, especially its automatic module, is supported by an extensive knowledge-base built into the software.

The global attention has always been focussed on the adverse environmental impacts of conventional energy sources. In contrast nonconventional energy sources, particularly the renewable ones, have enjoyed a ‘clean’ image vis a vis environmental impacts. The only major exception to this general trend has been large hydropower projects; experience has taught us that they can be disastrous for the environment. The belief now is that minihydel and microhydel projects are harmless alternatives. But are renewable energy sources really as benign as is widely believed? The present essay addresses this question in the background of Lovin's classical paradigm, which had postulated the hard (malignant) and soft (benign) energy concepts in the first place. It critically evaluates the environmental impacts of major renewable energy sources. It then comes up with the broad conclusion that renewable energy sources are not the panacea they are popularly perceived to be; indeed in some cases their adverse environmental impacts can be as strongly negative as the impacts of conventional energy sources. The paper also dwells on the steps we need to take so that we can utilize renewable energy sources without facing environmental backlashes of the type we got from hydropower projects.

The three aspects of accidents in chemical process industries which cause most serious damage—explosions, fires, and toxic releases—can all be controlled to some extent if greenbelts are present around the affected industry. We have recently developed and validated a system of methodologies for greenbelt design. In this paper we present the application of these models in designing greenbelts and forecasting their role in cushioning the impact of accidental release of toxic gases. With properly located and designed greenbelts as much as 33% of the accidental release of SO2, 43% of H2S, and 51% of NH3 under stable atmospheric conditions (in which the dispersion is very slow and the release thus has maximum toxic impact) can be absorbed.

Anaerobic digestion of municipal solid waste (MSW) was studied in ‘high solids digesters’ (HSDs) for generating energy (as methane). Three kinds of HSDs were employed in which the waste along with inoculum (consisting of pre-digested cow dung slurry) were subjected to anaerobic digestion. The first type (HSD-I) was provided with two chambers; the upper chamber served as a solid phase in which only the solid portions of vegetable waste were subjected to digestion, while the lower chamber served as liquid phase where the leachates were allowed to ferment. The second type (HSD-II) was similar to HSD-I but had no partition. The third type (HSD-III) had two distinct units, one for solid phase and the other for the liquid phase; the units were connected by a tap with a flow regulator valve. The reactor performance was assessed in terms of biogas yield. The results of the study indicate that the performance efficiency (in terms of biogas yield) of the HSDs increased with the increase in the degree of phase separ...

Fertilizer industries are among the chemical process industries where hazardous chemicals are handled and accidents involving heat/mass/momentum transfer can result in explosions, fires, and toxic releases. Based on experience gained from past incidents in the fertilizer industries risk assessment tools and techniques are often employed in order to identify hazards and to forecast potential disasters. These efforts have almost always focused on single events or “stand alone” accidents. The interaction of an accident with other hazardous units with the potential to cause secondary, tertiary, or higher order accidents is seldom studied. Yet, chain of accidents have been occurring in the past and the probability of a repetition in the future constantly increases because of the proximity of industrial plants and the increasing population pressure in most countries. Consequently we have developed models and computer-automated tools to study chain of accidents or “domino effects.” In this paper we discuss the concept of domino effect in the context of our methodologies, and present an illustrative case study of a major fertilizer industry situated near the city of Chennai(Madras, India).

The article draws attention towards the importance ofgreenbelts in attenuating gaseous pollutants andpresents the meteorological, physico-chemical,biological, and horticultural dimensions associatedwith effective greenbelt design.We have presented the gist of a system ofmethodologies, developed by us, for greenbelt design. A case study demonstrating the applicability of thesystem has been presented.

An expert system has been developed for automating HAZOP (HAZard and Operability) studies. The system, EXPERTOP (EXPERT system for conducting HAZOP) is capable of performing HAZOP studies at significantly lesser costs and with better accuracy than conventional HAZOP studies. By facilitating automation of HAZOP, EXPERTOP is expected to contribute significantly to the initiatives of the chemical process and other industries in conducting risk assessment. This, in turn, would contribute to an improvement in the production efficiency and, more significantly, risk minimisation of the industries. The latter aspect has assumed ever-increasing significance because frequency of industrial accidents has been increasing over the years as has the extent of damage caused by such accidents.

The paper describes the application of a new computer automated tool, developed by us, in the risk analysis of a typical chemical industry engaged in the manufacture of linear alkyl benzene. Using the tool—a comprehensive software package maxcred-III (MAXimum CREDible accident analysis)—nine different scenarios, one for each storage unit, have been studied. It is observed that the accident scenario for chlorine (instantaneous release followed by dispersion) leads to the largest area-under-lethal-impact, while the accident scenario for propylene (CVCE followed by fireball) forecasts the most intense damage per unit area. The accidents involving propylene, benzene, and fuel oil have a high possibility of causing domino/secondary accidents as their destructive impacts (shock waves, heat load) would envelope other storage and process units. Besides demonstrating the utilizability of maxcred-III, this study also focuses attention on the need to bestow greater effort towards risk assessment/crisis management. The authors hope that the study will highlight the severity of the risk posed by the industry and thus generate safety consciousness among plant managers. The study may also help in developing accident-prevention strategies and the installation of damage control devices.

This paper briefly recapitulates some of the major accidents in chemical process industries which occurred during 1926–1997. These case studies have been analysed with a view to understand the damage potential of various types of accidents, and the common causes or errors which have led to disasters. An analysis of different types of accidental events such as fire, explosion and toxic release has also been done to assess the damage potential of such events. It is revealed that vapour cloud explosion (VCE) poses the greatest risk of damage. The study highlights the need for risk assessment in chemical process industries.

The use of a new computer-automated tool TORAP (TOol for Rapid risk Assessment in Petroleum refinery and petrochemical industries) is demonstrated through a rapid and quantitative risk assessment of a typical petroleum refinery. The package has been applied for an appraisal of the risks of accidents (fires, explosions, toxic release) posed by different units of the refinery, and to identify steps to prevent/manage accidents. The studies reveal that TORAP enables a user to quickly focus on the accidents likely to occur, and enables forecasting the nature and impacts of such accidents. This information is directly utilisable in identifying “soft” spots and in taking appropriate remedial measures to prevent or control accidents. The special attributes of TORAP are: (a) a wide range of applications—achieved by incorporating models capable of handling all types of industrial fires and explosions, (b) sophistication—brought about by including state-of-the-art models developed by these authors and others, (c) user-friendliness—achieved by incorporating on-line help, graphics, carefully formatted output, and, above all, an automatic module with which even a lay user can conduct risk assessment. The entire package, especially its automatic module, is supported by an extensive knowledge-base built into the software.

Dispersion of several common `heavy' gases (ethylene, propylene, ammonia, and chlorine) has been modelled on the basis of modifications in plume path theory. The model takes into account, among other things, the variations in temperature, density, and specific heat during the movement of the heavy gas plume. The effects of wind speed, density of the gas, and venting speed on the plume dispersion have been simulated. Based on the simulations a set of empirical equations has been developed. The equations have been validated by theoretical as well as experimental studies. Studies have also been carried out to simulate the effect of venting speed (manipulated by injecting hot air with the released gas) on the plume dispersion. The study reveals that the effect of venting speed on dispersion is very pronounced and can be used to reduce the risk posed by the accidental luxurious release of toxic/flammable gases. For example an increase of 20% in venting speed of chlorine (54.1 m/s) can reduce the distance up to which toxic concentration would occur by about 1100 meters.

A methodology has been developed to conduct probabilistic fault tree analysis during risk assessment in chemical process industries. The methodology is based on a system involving (a) development of fault tree, (b) determination of minimum cutsets or shortest pathways leading from initiating events (malfunctioning) to the top event (the major accident), (c) probability analysis, and (d) working out improvement index values. To this end techniques of Boolean algebra, structure moduling, analytical method of cutsets finding (top-to-bottom algorithm), Monte-Carlo simulation, optimization technique and fuzzy probability set have been used. We named the methodology Analytical -Simulation Methodology (ASM) and we developed a software package PROFAT (PRObabilistic fault tree analysis) to facilitate the use of the methodology in a rapid and eflective, yet user-friendly manner. PROFAT enables the user to find out, in an industry, (i) initiating events which may eventually lead to a major accideizt, (ii) shortest routes (minimum cutsets) a series of initiating events may take place while aiding each other in causing the accideizt. (iii) the probabilities of occurrence of such initintirig events, (iv) relative contributiom of each of the initiating events and, finally, (v) identfiing initiating events with the greatest potential to cause the top event (major accident) so that accident prevention strategies aud emergency preparedness plans can be focused on them. The noteworthy attributes of the system are: resilience towards lack of precision in the basic data, swift processing with moderate requirements of computation cupacity (sophistication of computers needed), ease of use, and direct1y utiliz-able output. The applicability of PROFAT has been denionstrated with a case study of a sulfolane manufacturing unit.

The world's most destructive industrial accident of the current decade, in terms of human lives lost (over 60) and damage to property (over $15 million), occurred at the petroleum refinery of Hindustan Petroleum Corporation Limited (HPCL) at Vishakhapatnam, India, on September 14, 1997. In this paper we have used two computer automated tools recently developed by us, MAXCRED [7], and DOMIFFECT [8], to determine their ability to forecast the details of the incident. When the situation at Vishakhapatnam, prior to the accident, was studied with MAXCRED for potential accidents and their likely consequences, the tool was able to generate a scenario which forecast the incident quite closey. We then used MAXCRED and DOMIFFECT to tell us what else might have occurred. The prognosis is quite scary. The computer tools reveal a few lucky breaks: had the situation and the events conspired a little more treacherously, the HPCL disaster would have been much larger in magnitude. Indeed the incident could have resulted in a death toll of the magnitude of the Bhopal Gas Tragedy with additional massive damage to propert. This paper show-cases the usefulness of MAXCRED and DOMIFFECT and also brings forth lessons which all industries would benefit from learning.

FPGA based implementation and VHDL based design of a reconfigurable CRC code generator chip with a CRC of 16 bits using a powerful byte-wise rather than the conventional bit-wise algorithm is presented. The hardware design and simulation has been carried out with the help of high level design environment tools using VHDL. The circuit has been simulated and implemented in FPGA. The approach adopted is absolutely general and can be extended to other types of CRC's as well. The CRC chip has all the inherent advantages of FPGA and has applications in areas such as error detection and correction in data communication and signature analysis.

The importance of inherently safer design (ISD) as a strategy to minimize risk of accidents in chemical process industries is being repeatedly stressed in recent years. The increasing number, frequency, and extents of damage caused by such accidents across the world have contributed to this thinking. However even as the need for ISD is being underscored, there are very few reports on precise methods to implement this concept. Significant recent reports are by Berge (1993 Berge, 1995) who has suggested a scenariobased design procedure in which construction of accident scenarios in a structured manner is made the basis of ISD. We have been developing and applying the concept of rapid risk analysis ( Khan & Abbasi, 1995 , Khan & Abbasi, 1996 , Khan & Abbasi, 1997a , Khan & Abbasi, 1997b , Khan & Abbasi, 1998a , Khan & Abbasi, 1998b ). In this paper we present an approach to ISD utilizing this concept. We believe, as detailed in this paper, that this approach is a significant improvement upon Berge's procedure in terms of ease, speed, and effectiveness.

A new software package for conducting rapid risk assessment (RRA) in chemical process industries and the system of methodologies on which it is based are described. The objectives behind the development of the package are to achieve greater breadth and depth, sophistication, and user-friendliness in conducting RRA. In pursuit of these objectives we have incorporated in the package state-of-the-art models for generating accident scenarios and assessing their consequences. The package has been coded in C++ using the concepts of object-oriented programming to enhance the tool's speed of execution and ease of use. The paper also demonstrates the applicability of MAXCRED with an illustrative example of a RRA conducted with its assistance.

This paper presents a state-of-art-review of the available techniques and methodologies for carrying out risk analysis in chemical process industries. It also presents a set of methodologies developed by the authors to conduct risk analysis effectively and optimally.

Most of the past risk assessment studies deal with accidents in a single industry, more so in one of the units of an industry. However, it is always possible that an accident in one unit can cause a secondary accident in a nearby unit which in turn may trigger a tertiary accident, and so on. The probability of occurrence and adverse impacts of such domino or cascading effects are increasing due to increasing congestion in industrial complexes and increasing density of human population around such complexes. This is particularly so in developing countries. The recent disaster at a refinery in Vishakhapatnam, India, which claimed over 60 lives and damaged property worth Rs 600 million, has brought the damage potential of domino effect into sharp focus. This paper presents a new computer automated tool DOMIFFECT (DOMIno eFFECT) which is the first ever such tool reported for studying domino effects. The package is capable of a) estimating the hazards of fire, explosion, toxic release, or combination of these present in a chemical process industry; b) the damage potential of likely accidents, assessed on the basis of credible scenarios the tool develops; c) the likelihood of a second accident being triggered by the first, d) the scenarios of the second accident, their damage potential, and the probability of their causing a third accident (steps similar to a–c above), and so on. The software has been coded in C++ and has the attributes i) wide applicability, ii) sophistication, iii) user friendliness, and iv) flexibility for improvement.

Accidents involving toxic releases, explosions, and fires in chemical process industries take a heavy toll of property, human lives, and environment quality. If one could forecast the accidents likely to occur and the damage they were likely to cause, one could devise appropriate strategies to prevent the accidents and contain the damage that did occur. Using this concept, we have developed a computer-automated tool for accident simulation. In this paper the applicability of the concept and the tool is described on the basis of a case study of a typical petrochemical industry. The study reveals that out of eight credible accident scenarios, four would be ’stand-alone’ events, whereas four others would also cause secondary or higher order accidents (domino effects). Of the accidents in the former category, the one as per scenario 8 is the worst as it would adversely impact (within the set limit of 50 % probability of causing lethality) larger areas than the other three such accidents. Among the second category, scenario 1 would be the most undesirable because it would simultaneously cause heat radiation, shock waves, and missile effects over a larger area.

Petrochemical industries use hazardous chemicals and processes which have the potential to cause major accidents if human or equipment failure occurs. As most such industries are situated close to densely populated urban or rural locations, especially so in developing countries, it is very important to study the accidents that may take place, and the damage these may cause, so that preventive/mitigative measures may be taken before any tragedy does occur. Such a study would also contribute towards evolving strategies for cleaner functioning of these industries. In this paper we have conducted a detailed risk assessment study of a typical petrochemical industry using the software package MAXCRED recently developed by us. The study has two objectives, (a) to provide a quantitative assessment of the accidents likely to be caused and the damage potential (as inputs for crisis prevention/management) and (b) to demonstrate the viability of MAXCRED as a user friendly tool for rapid risk assessment. It also suggests some measures to control the risk potential. The authors hope that these studies would highlight the severity of risk posed by the industry and would thus generate safety consciousness among plant managers. The studies may also help in developing accident-prevention strategies and installation of damage control devices.

In the risk assessment parlance, especially with reference to chemical process industries, the term “domino effect” is used to denote “chain of accidents,” or situations when a fire/explosion/missile/toxic load generated by an accident in one unit in an industry causes secondary and higher order accidents in other units. The multi-accident catastrophe which occurred in a refinery at Vishakhapatnam, India, on September 14, 1997, claiming 60 lives and causing damages to property worth over Rs 600 million, is the most recent example of the damage potential of domino effect. But, even as the domino effect has been documented since 1947, very little attention has been paid towards modeling this phenomena. In this paper we have provided a conceptual framework based on sets of appropriate models to forecast domino effects, and assess their likely magnitudes and adverse impacts, while conducting risk assessment in a chemical process industry. The utilizability of the framework has been illustrated with a case study.

Risk analysis in chemical process industries is an elaborate exercise involving several steps from preliminary hazard identification to development of credible accident scenarios, to preparation of strategies for prevention or control of damage. All this requires substantial inputs of time and money. In order to get an approximate yet workable assessment of risk at much lesser costs, indices have been developed which link typical findings of elaborate risk analysis to scales of risk. The scales, in turn, provide workable measures of hazards/risks/safety. In the past, indices have been reported for swift risk assessment—the noteworthy among them include Dow fire and explosion index, Mond fire, explosion and toxicity index, IFAL index, and mortality index. A few rapid ranking techniques have also been proposed. This paper presents a new system of methodologies for Hazard Identification and Ranking (HIRA). The system consists of two indices: one for fire and explosion hazards and another for the hazard due to likely release of toxic chemical. The magnitudes of these indices indicate the severity of the likely accident; in terms of the size of the impacted area. HIRA has been applied to a typical chemical process industry—a sulfolane plant—and its performance has been compared with that of the Dow's and the Mond's indices. The study reveals that HIRA is more sensitive and accurate than the other indices.

A biomimetic method of gold nanoparticle (AuNP) synthesis is presented which utilizes a terrestrial weed guduchi (Tinospora cordifolia), as the main bioagent. The method enables rapid synthesis of AuNPs at ambient temperature and pressure, with frugal energy use and no harmful emissions. It is possible to control the shape and size of the product by controlling the metal−bioagent stoichiometry. The electron micrographs of the synthesized AuNPs reveal the presence of particles of either monodispersed spherical or polydispersed triangular, pentagonal, and hexagonal shapes in sizes of 16-30 nm and 25-75 nm respectively. The presence of gold atoms was confirmed from the EDAX and X-ray diffraction studies. FT-IR spectral study indicated that the alkaloids in the plant extract could have been responsible for the reduction−cum−stabilization of the gold ions into AuNPs.

Hazard and operability (HAZOP) studies constitute an essential step in the risk analysis of any chemical process industry and involve systematic identification of every conceivable abnormal process deviation, its causes and abnormal consequences. These authors have recently proposed optHAZOP as an alternative procedure for conducting HAZOP studies in a shorter span of time than taken by conventional HAZOP procedure, with greater accuracy and effectiveness [Khan, F. I. and Abassi, S. A., optHAZOP. An effective and efficient technique for hazard identification and assessment Journal of Loss Prevention in the Process Industries, 1997, 10, 191–204]. optHAZOP consists of several steps, the most crucial one requires use of a knowledge-based software tool which would significantly reduce the requirement of expert man-hours and speed up the work of the study team. TOPHAZOP (Tool for OPTmizing HAZOP) has been developed to fulfil this need. The TOPHAZOP knowledge-base consists of two main branches: process-specific and general. The TOPHAZOP framework allows these two branches to interact during the analysis to address the process-specific aspects of HAZOP analysis while maintaining the generality of the system. The system is open-ended and modular in structure to make easy implementation and/or expansion of knowledge. The important features of TOPHAZOP and its performance on an industrial case study are described.

To conduct effective and efficient HAZOP (Hazard and Operability) study it is essential that the study should be planned and managed well. The planning and management can be done effectively only when the various steps of the study, scope of each step, and duration of each step are well defined. Significant work has been done over the identification of various applications of HAZOP, but not much work has been done over HAZOP study duration estimation, which is a key parameter for proper planning and management of HAZOP study. Freeman et al. (1992) [6] have proposed a model for HAZOP study time (duration) estimation, however, it still needs modification in terms of easy application and more reliable estimation. The present work is an effort in the same direction, a mathematical model being proposed to forecast (estimate) the HAZOP study duration for varying capacity and complexity of the problem. The accuracy of the results has been checked with some of the past case studies carried out by various agencies. It has been observed that the authors' model predicts result with accuracy of about 90–95%, while Freeman's model is restricted to 85–90%. Moreover, the proposed model is simple, easy to implement, and can be automated to software.

Qualitative hazard assessment is part of the detailed risk analysis of chemical process industries and a hazard and operability (HAZOP) study is the best technique to carry out this step. It is a systematic study conducted by a team of experts of different disciplines to identify and assess hazards using brainstorming discussion of deviation in operational parameters from normal/standard conditions. This study needs high levels of expertise and substantial time commitments. The various steps involved in any typical HAZOP (application of deviation, cause-finding, and consequence analysis of each and every line and equipment) need a sustained high level of mental performance and alertness for a long span of time, but the repetitious nature of these steps inevitably generates a feeling of drudgery and mental fatigue, even exhaustion. This may not only reduce the effectiveness of HAZOP, but even render it incomplete or erroneous. This paper is devoted to a discussion about the factors that have direct influence on the efficiency, effectiveness and reliability of such studies. It also suggests an optimal approach to HAZOP study procedures (optHAZOP) based on the utilization of an already developed information base. The optHAZOP technique reduces the mental execution load of experts by a half, and thus provides more time to study typical hazardous units and conceptualize better control strategies. This technique takes around 45% less time than that of the conventional HAZOP study procedure (estimated using CPM networking and time analysis of different steps of study) with better efficiency and effectiveness.

Studies pertaining to risk analysis, conducted on the storage units of a typical chemical industry engaged in the manufacture of epichlorohydrin, are described. A comprehensive software package MAXCRED (MAXimum CREDible accident analysis) recently developed by us has been utilized for the purpose. Eight different scenarios, one for each storage unit, have been studied. It is observed that the accident scenario for chlorine (BLEVE followed by dipersion) leads to the largest area-under-lethal-impact while the accident scenario for propylene (CVCE followed by fire ball) forecasts the most intense damage per unit area. The accidents involving propylene, epichlorohydrin and fuel oil have high possibility of causing domino/secondary accidents as their destructive impacts (shock waves, heat load) would envelope other storage and process units. Besides demonstrating the utilizability of MAXCRED, this study also focuses attention on the need to bestow greater effort towards risk assessment/crisis management. The authors hope that these studies would highlight the severity of risk posed by the industry and would thus generate safety consciousness among plant managers. The studies may also help in developing accident-prevention strategies and installation of damage control devices.

Picture synchronization is indispensable for proper reception in a television system. Complex synchronization signals are transmitted along with the picture information for proper reproduction of the picture at the receiver. A totally different design methodology has been adopted for the generation of complex synchronizing (sync) signals as compared to the one reported earlier, so as to reduce the memory size from 8 K to only 226 bytes. This massive reduction in memory size made it possible to implement the whole design in a highly miniaturized single FPGA. Since the sync signals are complicated, a PROM is used to hold the waveform. In order to reduce the memory size, the basic time durations are chosen judiciously. Moreover, the repeatability of the waveform is exploited by introducing looping in hardware at different places.

Risk assessment, based on quantitative maximum credible accident analysis (MCAA), has been conducted for a chloralkali industry situated in the midst of densely populated coastal villages. The study has made use of a software package MAXimum CREDible accident analysis version 2 (henceforth referred to as MAXCRED-II) recently developed by us. Among the six different most credible accident scenarios developed using MAXCRED-II, the one envisaging ‘confined vapor cloud explosion followed by fire ball’ (in the hydrogen storage vessel) comes out to be the worst in terms of the highest propensity for damage (overpressure, missile, heat load). It also has the potential of causing domino effect (chain of accidents). The scenario of causing domino effect (chain of accidents). The scenario of ‘continuous release of chlorine from storage vessel’ is the second most disastrous, in terms of lethal toxic load likely over a large distance (3252 meters). In summary, the study reveals that given the masses of materials stored, and the conditions in which they are stored, there is a live risk of accidents in the storage vessels that would have far-reaching consequences. The industry thus poses a great risk to large areas of surrounding including densely populated villages (particularly Chinnakalapet and Kalapet) and the campuses of Pondicherry University and Pondicherry Engineering College. This paper demonstrates the utilizability of MAXCRED-II and also focuses attention on the need to bestow greater effort towards risk assessment. It is hoped that these studies will make plant managers conscious of the serious consequences that can result from accidents in their vulnerable units. Appreciation of the risk, we hope, will prompt them to develop accident prevention strategies and to put in position emergency preparedness plans to cushion the adverse impacts if accidents do occur.

Renewable energy sources are widely perceived as ‘clean’, ‘green’, and ‘inexhaustible’. In recent years the spectre of global warming and ocean acidification, which has been primarily attributed to fossil fuel burning, has brought renewable energy at the forefront of most climate change mitigation strategies. There is strong advocacy for large-scale substitution of conventional energy sources with the renewables on the premise that such a move would substantially reduce environmental degradation and global warming. These sentiments are being echoed by scientists and policy makers as well as environmental activists all over the world. ‘Small hydro’, which generally represents hydroelectric power projects of capacities 25 MW or lower, is one of the renewable energy options which is believed to be clean and sustainable even as its bigger version, large hydro, is known to cause several strongly adverse environmental impacts. This paper brings out that the prevailing perception of ‘eco-friendliness’ of small hydro is mainly due to the fact that it has only been used to a very small extent so far. But once it is deployed at a scale comparable to fossil fuel use, the resulting impacts would be quite substantially adverse. The purpose is not to denegrade small hydro, less so to advocate use of fossil fuels. It, rather, is to bring home the point that a much more realistic and elaborate assessment of the likely direct as well as indirect impacts of extensive utilization of this energy source than has been done hitherto is necessary.

It has been estimated that livestock manure contributes about 240 million metric tons of carbon dioxide equivalent of methane to the atmosphere and represents one of the biggest anthropogenic sources of methane. Considering that methane is the second biggest contributor to global warming after carbon dioxide, it is imperative that ways and means are developed to capture as much of the anthropogenic methane as possible. There is a major associated advantage of methane capture: its use as a source of energy which is comparable in 'cleanness' to natural gas. The present review dwells upon the traditional ways of methane capture used in India, China, and other developing countries for providing energy to the rural poor. It then reviews the present status of methane capture from livestock manure in developed countries and touches upon the prevalent trends.

Even as each and every water-quality index (WQI) is potentially utilisable in the planning of water resource protection, redemption and utilisation, some WQIs have been specifically developed to aid in environmental planning and decision making. This chapter describes several of the important planning and decision-making indices that have been reported so far.

Even as a large number of countries do not have even nation-specific WQIs, the USA and Canada have not only national WQIs but also several state-specific WQIs. Moreover, the WQIs of both countries have been used by other countries, either directly or with minor modifications. Hence, this chapter has been devoted to a review of the WQIs of these two countries.

This chapter is the first of the three chapters which describe avenues by which uncertainties inherent in crisp and deterministic approaches to water-quality monitoring, analysis and index development are side-stepped. Indices using relatively advanced techniques and tools of statistics have been described in this chapter.

Multivariate methods for bioassessment of water quality aim to be more ‘objective’ than biotic indices (BI) and indices of biotic integrity (IBI) described in the preceding chapters. In the multivariate approaches, statistical tools are used to develop relationships between fauna and water quality for an ‘ideal’ or high-quality reference site. The relationships are used to predict the fauna at any test site in the absence of pollution (or other type of stress). The observed fauna at the test site is then compared with the fauna expected at that site to make assessments of water quality at the test site.

The only one software reported so for, which is capable of generating water-quality indices, is described. The concept of ‘virtual water-quality meter’ is also presented.

This introductory chapter speaks about the difficulty inherent in quantifying and expressing water quality in contrast to the ease with which water quantity can be specified. The chapter then introduces the concept of water-quality indices with which the highly multiple-attribute aspect of water quality can be resolved into a single score. The various ways in which water-quality indices facilitate water-quality assessment and management are highlighted. The concept is elaborated by drawing parallels with share-market indices and is illustrated with the example of the first-ever modern WQI – the Horton's index – which was introduced in 1965.