Devendra Saroj

A group decision-making tool for the application of membrane technologies in different water reuse scenarios

A global challenge of increasing concern is diminishing fresh water resources. A growing practice in many communities to supplement diminishing fresh water availability has been the reuse of water. Novel methods of treating polluted waters, such as membrane assisted technologies, have recently been developed and successfully implemented in many places. Given the diversity of membrane assisted technologies available, the current challenge is how to select a reliable alternative among numerous technologies for appropriate water reuse. In this research, a fuzzy logic based multi-criteria, group decision making tool has been developed. This tool has been employed in the selection of appropriate membrane treatment technologies for several non-potable and potable reuse scenarios. Robust criteria, covering technical, environmental, economic and socio-cultural aspects, were selected, while 10 different membrane assisted technologies were assessed in the tool. The results show this approach capable of facilitating systematic and rigorous analysis in the comparison and selection of membrane assisted technologies for advanced wastewater treatment and reuse.

Assessment of biological trickling filter systems with various packing materials for improved wastewater treatment

Attached growth processes for wastewater treatment have significantly been improved during recent years. Their application can be extended to sustainable municipal wastewater treatment in remote locations and in developing countries for the purpose of organic matter (biochemical oxygen demand, BOD) removal and pathogenic decontamination. The aim of this study is to assess selected packing media for biological trickling filters (BTFs) and to develop a simplified model for describing the capacity of BOD removal in BTFs. In this work, BTFs with four different media viz., rubber, polystyrene, plastic and stone have been investigated at two temperature ranges of 5–15°C and 25–35°C. The average removal of both chemical oxygen demand and BOD was higher than 80 and 90% at temperature ranges of 5–15 and 25–35°C, respectively. The geometric mean of faecal coliforms in BTF using polystyrene, plastic, rubber and stone as filter media was reduced by 4.3, 4.0, 5.8 and 5.4 log10, respectively, at a low temperature range of 5–15°C. At a higher temperature range of 25–35°C, the faecal coliform count was reduced by 3.97, 5.34, 5.36 and 4.37 log10 from polystyrene, plastic, rubber and stone media BTF, respectively. Simplified model was developed and used to estimate the optimal BOD loading rates (Bvd) for designing robust BTF systems, with appropriate filter media. It has been concluded that highly efficient BTFs can be designed using various filter media, which may be capable of treating organic loading rates of more than 3 kg BOD/m3 day. These types of BTFs can be applied for the BOD and microbial contaminants removal of wastewater for potential reuse in developing countries.

Comparison of phosphorus recovery from incinerated sewage sludge ash (ISSA) and pyrolysed sewage sludge char (PSSC)

This research compares and contrasts the physical and chemical characteristics of incinerator sewage sludge ash (ISSA) and pyrolysis sewage sludge char (PSSC) for the purposes of recovering phosphorus as a P-rich fertiliser. Interest in P recovery from PSSC is likely to increase as pyrolysis is becoming viewed as a more economical method of sewage sludge thermal treatment compared to incineration. The P contents of ISSA and PSSC are 7.2-7.5% and 5.6%, respectively. Relative to the sludge, P concentrations are increased about 8-fold in ISSA, compared to roughly 3-fold in PSSC. Both PSSC and ISSA contain whitlockite, an unusual form of calcium phosphate, with PSSC containing more whitlockite than ISSA. Acid leaching experiments indicate that a liquid/solid ratio of 10 with 30min contact time is optimal to release PO4-P into leachate for both ISSA and PSSC. The proportion of P extracted from PSSC is higher due to its higher whitlockite content. Heavy metals are less soluble from PSSC because they are more strongly incorporated in the particles. The results suggest there is potential for the development of a process to recover P from PSSC.

Removal of organic micropollutants using membrane-assisted processes: a review of recent progress

The health risk of organic micro pollutants in water is yet to be comprehensively established. However, the persistence of these pollutants in the environment as a result of continuous discharge even at trace concentrations is considered to pose major environmental concerns. Advance treatment methods such as membrane-assisted processes (MAPs) are potential technologies capable of removing a wide range of these organic micropollutants (OMPs) detected in water. Tight membranes as regards pore size are reported to be more efficient than loose membranes mainly because of the removal mechanism involved, which is mainly influenced by the properties of the membrane and the pollutants in relation to solute–solute and solute–membrane interaction. The study and application of membrane processes to water and wastewater treatment have grown significantly in the last decade. Membrane processes application is diverse and flexible enough to allow adaptation into other physicochemical processes. Integration and hybridization of membrane processes with other physicochemical processes and natural systems are becoming a more economical and sustainable option for removal of OMPs. Nevertheless, there are shortfalls in the industrial application of membrane-assisted technologies. This paper reviews and assesses the applicability of various MAPs applied for the removal of OMPs from water and wastewater streams.

Membrane technologies for municipal wastewater treatment

The occurrence of emerging or newly identified contaminants in water resources is becoming a great concern for public health. The worldwide freshwater scarcity is also increasing. These have resulted in rapid growth in the demand for nonconventional water resources and sophisticated approaches to wastewater treatment. Existing conventional water treatment plants were not designed for these emerging contaminants. Therefore, new approaches to wastewater treatment are required. Among the most promising processes for various types of wastewater treatment and water reuse, membrane-assisted technologies have been accepted as suitable and reliable in different applications of water reuse. This chapter discusses the application of membrane processes and membrane-assisted technologies in wastewater treatment and water reuse. The chapter mainly focuses on membrane bioreactors (MBRs), including a comparison between conventional activated sludge processes and MBRs. Emerging membrane-assisted technologies are also discussed.

Membrane assisted technology appraisal for water reuse applications in South Africa

Water scarcity, pertaining to many interrelated issues e.g. rapid urbanisation and increasing water pollution, has been acknowledged around the world. Water reuse has emerged as a viable water conservation measure to satisfy water demand in many communities. Among the diversity of wastewater treatment processes, membrane assisted treatment technologies have been employed for different water reuse scenarios. In this regard, one of the most critical problems is how to select an appropriate membrane technology for a water reuse scenario. This research therefore develops a decision making framework for selection of wastewater treatment technology. The framework is applied to different non-potable reuse scenarios in South African cities and suburban areas by employing a multi criteria analysis method. The results show that this approach is able to provide a systematic and rigorous analysis which can help in comparing and selecting wastewater technologies.

Membrane reactors for bioethanol production and processing

Dwindling supplies of fossil fuel along with detrimental release of greenhouse gases have led to the quest for renewable sources of fuel such as bioethanol from cellulosic materials. Conversion of biomass to bioethanol involves a set of “biotransformation” and “recovery/concentration” processes. With the help of membrane technology, several process steps that were conventionally separate can be integrated and the production of bioethanol simplified. In addition to efficient recovery of bioethanol, this can facilitate removal of inhibitory side products from the fermentation broth and recovery of the inhibitory but valuable side products. This chapter provides a critical review of the application of membrane technology in various steps of bioethanol production. The challenges to widespread deployment of full-scale bioethanol facilities equipped with membranes have also been outlined.

Physiological activities associated with biofilm growth in attached and suspended growth bioreactors under aerobic and anaerobic conditions.

This research work evaluated the biofilm succession on stone media and compared the biochemical changes of sludge in attached and suspended biological reactors operated under aerobic and anaerobic conditions. Stones incubated (30 ± 2°C) with activated sludge showed a constant increase in biofilm weight up to the fifth and seventh week time under anaerobic and aerobic conditions, respectively, where after reduction (>80%) the most probable number index of pathogen indicators on ninth week was recorded. Reduction in parameters such as biological oxygen demand (BOD) (47.7%), chemical oxygen demand (COD, 41%), nitrites (60.2%), nitrates (105.5%) and phosphates (58.9%) and increase in dissolved oxygen (176.5%) of sludge were higher in aerobic attached growth reactors as compared with other settings. While, considerable reductions in these values were also observed (BOD, 53.8%; COD, 2.8%; nitrites, 28.6%; nitrates, 31.7%; phosphates, 41.4%) in the suspended growth system under anaerobic conditions. However, higher sulphate removal was observed in suspended (40.9% and 54.9%) as compared with biofilm reactors (28.2% and 29.3%). Six weeks biofilm on the stone media showed maximum physiological activities; thus, the operational conditions should be controlled to keep the biofilm structure similar to six-week-old biofilm, and can be used in fixed biofilm reactors for wastewater treatment.

Removal of Escherichia coli and heavy metals from aqueous solutions using silver-modified clinoptilolite

AbstractThe aim of this study was to investigate the removal of Escherichia coli and heavy metals (Pb2+, Cd2+ and Zn2+) from aqueous solutions using silver-modified clinoptilolite through the combined disinfection of E. coli by the silver ions and sorption of heavy metals on clinoptilolite. The silver-modified zeolites exhibited excellent disinfection performance with 100% removal of E. coli within 30 min. The as-received natural zeolites showed no disinfection characteristics under the same conditions. High metal removal efficiencies up to 92% were achieved with respect to the metals present in solution. In the E. coli-metals solution systems, disinfection was enhanced by the presence of metal ions which resulted in a relatively reduced amount of metals adsorbed by the zeolites due to the uptake of metal ions by the bacterial cells present the solution. The results of this study demonstrate that silver-modified clinoptilolite has a potential for the simultaneous removal of metals and pathogenic organisms...