Significance of natural treatment systems to enhance reuse of treated effluent: A critical assessment

This paper summarizes the results of the recently completed India-wide survey of 108 wastewater treatment facilities based on natural treatment systems (NTSs) engaged in wastewater treatment and reuse. During assessment of NTSs, a questionnaire survey was administered for collection of vital data on the shortlisted 41 treatment facilities - especially to obtain insights about the technical, economical and social issues influencing the success and failure of the given facility. Further, five case studies based on the most commonly practiced NTSs were selected for in-depth evaluation and the critical issues including effectiveness of technology and the socioeconomic aspects were studied. The treatment performance of these systems was assessed for one year by collecting primary data during January, June and August corresponding to the three seasons viz. winter, summer and monsoon. The effectiveness of the facilities was assessed in terms of percentage removals as well as the mass removal rate for commonly used parameters. As of today, the total load of sewges including sullages serviced by NTSs in India adds up to be around 1838 million liters a day. The most commonly practiced NTS in India has been the waste stabilization ponds (74 facilities) when compared with the phyto-remediation based systems (19 facilities) followed by the polishing ponds (15 facilities). Among the 41 facilities, nearly 75% facilities were compliant and managed to produce treated sewages suitable for irrigation, discharged into wastewater canals or percolated in the riparian zone of the river. All the five systems that were selected for in-depth evaluation were found compliant during assessment. Also, two facilities (Sewage-fed Aquaculture Karnal and Duckweed Pond Ludhiana) were found to be operating on the public private partnership model and generating revenue for operation and maintenance along with ample benefits to the operating agencies. The study also reveals the associated socioeconomic benefits of various practiced NTSs. Finally, strategies for achieving improved performance of NTSs were articulated - especially focusing the potential for recycling and reusing of treated wastewaters. (C) 2016 Elsevier B.V. All rights reserved

Evaluation of substrate removal kinetics for UASB reactors treating chlorinated ethanes

Lack of focus on the treatment of wastewaters bearing potentially hazardous pollutants like 1,1,2 trichloroethane and 1,1,2,2 tetrachloroethane in anaerobic reactors has provided an impetus to undertake this study. The objective of this exercise was to quantify the behavior of upflow anaerobic sludge blanket reactors and predict their performance based on the overall organic substrate removal. The reactors (wastewater-bearing TCA (R2), and wastewater-bearing TeCA (R3)) were operated at different hydraulic retention times (HRTs), i.e., 36, 30, 24, 18, and 12 h corresponding to food-to-mass ratios varying in the range of 0.2-0.7 mg chemical oxygen demand (COD) mg(-1) volatile suspended solids day(-1). The process kinetics of substrate utilization was evaluated on the basis of experimental results, by applying three mathematical models namely first order, Grau second order, and Michaelis-Menten type kinetics. The results showed that the lowering of HRT below 24 h resulted in reduced COD removal efficiencies and higher effluent pollutant concentrations in the reactors. The Grau second-order model was successfully applied to obtain the substrate utilization kinetics with high value of R (2) (> 0.95). The Grau second-order substrate removal constant (K (2)) was calculated as 1.12 and 7.53 day(-1) for reactors R2 and R3, respectively. This study demonstrated the suitability of Grau second-order kinetic model over other models, for predicting the performance of reactors R2 and R3, in treating wastewaters containing chlorinated ethanes under different organic and hydraulic loading conditions

Study of different image windowing on Turbidity regression model using remotely sensed data

The Thane creek region, near Mumbai city is being used as dumping site for treated and untreated effluents by government agencies and private industries for the last several decades. This coastal water is very important from environmental point of view since it supports a vast area of mangrove forest besides a wide variety of flora and fauna. Turbidity, an important marine physical pollution parameter, affects the growth of mangroves, causes loss of swamps and poses threat to aquatic life. The work presented discusses the effect of 'variations in sampling time' on Turbidity regression model using Remotely Sensed Data. Marine water samples were collected synchronous to pass of Landsat satellite and Turbidity (NTU) was measured (During the post monsoon season of 1996/97 window of sample collection was +/- 1 hour, which was reduced during the post monsoon season of 1997/98 to 15 minutes). The digital satellite images were corrected initially for geometric, sun angle and atmospheric errors. From the corrected remotely sensed data, DNs values were extracted. Multiple regression model was developed between water quality parameter, turbidity and extracted Digital Numbers (DNs) from corresponding sampling locations by varying image window sizes (Le. 1x1, 3x3 and 5x5 pixels). It was deduced that averaging 3X3 window corresponding to water sample collection locations followed by multiple regression with water quality parameter, turbidity, gave best results of regression coefficient

Post-treatment and reuse of secondary effluents using natural Itreatment systems: the Indian practices

Paper summarizes the results of India-wide survey of natural treatment systems (NTSs) for wastewater treatment and reuse. The quality of treated wastewater from different types of NTSs was analyzed for various physico-chemical and bacteriological parameters, and needs for post-treatment were identified. Currently, about 1838 million liters per day (MLD) of wastewater is being treated using NTSs, of which the contributions of polishing ponds, waste stabilization ponds, duckweed ponds, constructed wetlands, and Karnal technology were found to be 53.39, 45.15, 0.13, 0.55, and 0.78 %, respectively. Among the NTSs studied, constructed wetland was found most efficient in removal of pollutants including nitrogen, phosphorus, total coliform, and fecal coliform in the range of 76, 61, 99.956, and 99.923 %, respectively. Of all types of NTSs, only constructed wetland was found to meet the total coliform count requirements (<1000 per 100 ml). Of all the 108 NTSs in operation, 23 systems are producing treated effluents for irrigation; effluents from 48 systems are being discharged into river or lake, and remaining 38 systems have not found any designated use of treated effluent. The chlorination was the only post-treatment, which is being practiced at only three wastewater treatment facilities. During post-treatment, 1-2 ppm of chlorine is applied to the secondary effluent irrespective of its quality. The treated effluents from different NTSs contain fecal bacteria in the magnitude of 103 to 105, which may cause the severe health impacts through contamination of groundwater as well as surface water resources

Modeling of biological particle mixing in a fluidized-bed biofilm reactor

Performance of fluidized-bed biofilm reactors (FBBRs) greatly depends on the amount of biomass attached to the inert core support particles and overall bed voidage. Thus, for proper design of an FBBR, it is important to know the biological particle (bioparticle) mixing and bed expansion behavior, which in turn influence bed volume and consequently the residence time of the liquid phase. This paper first investigates the superiority of some of the predominantly used fluidization correlations for biological beds to predict bed voidage and, second, it investigates the implications of bioparticle mixing in FBBRs. The fluidization correlation suggested by Foscolo et al. (1983) was found to be superior to the more widely used Richardson and Zaki (1954) correlation to predict FBBR bed voidage. Furthermore, from the three different sets of published experimental results of bed voidage applied in this study, the fluidization correlation suggested by Foscolo et al. (1983), along with the terminal settling velocity equation suggested by Mulcahy and Shieh (1987), was found to be superior to other sets of correlations used in this study to predict bed voidage in an FBBR, having the lowest mean deviation of 12.7%. A mathematical model for fluidization of a binary bioparticle mixture is also presented in this paper to model the interaction of a variety of parameters, including upflow superficial liquid velocity, core support particle size and density, and biofilm thickness. Numerical simulations using this model revealed that, for sand-like core support particles (density ranging from 1500 to 2700 kg/m(3)), a complete segregation would likely occur in the bed with larger bioparticles at the top and smaller ones at the bottom. For charcoal- or polymer-like core support particles (density ranging from 1050 to 1300 kg/m(3)), a homogeneous bed made up of both larger and smaller bioparticles would likely occur. Comparison of the model predictions with published experimental results suggested excellent agreement

Life cycle-based decision support tool for selection of wastewater treatment alternatives

We report the development and application of a user-friendly, scenario-based decision support tool (TechSelect 1.0). The objective of the study focuses on implementation of the 'scenario-based' multiple attributes decision-making (MADM) approach recently proposed by Kalbar et al. (2012a). The tool incorporates multiple scenarios to deal with complex decision-making situations typically encountered in urban, suburban and rural areas. The scenario-based decision-making implemented through the tool reduces complexity in the selection of the appropriate wastewater treatment technology. It also uses a life cycle sustainability assessment framework for assessing technologies from environmental (life cycle assessment), economic (life cycle costing) and social (various sustainability indicators) perspectives. In addition, a user-friendly computational platform has been provided for the convenience of end users and stakeholders. The tool has been tested and validated on two real-life case studies pertaining to the problem of decision-making under complex situations. The results clearly explain the technology selection process and justify the simplicity of the tool in both the case studies. The proposed tool will broaden the application of scenario-based decision-making approaches in wastewater management. (C) 2016 Elsevier Ltd. All rights reserved

Bed voidage correlation in fluidized bed biofilm reactor

A simple predictive correlation for bed voidage in a three-phase fluidized bed biofilm reactor (FBBR) has been proposed in this study, based on a relationship between the effective up-flow superficial liquid velocity (U-L) and the corresponding up-few superficial liquid velocity in a three-phase FBBR (U-L'). The experimental observations of bed voidage both for this study as well as for experimental data from a study Trinet et al. for a three-phase FBBR compared reasonably well with the model predictions developed in this study, with mean deviations of 0.26% and 7%, respectively. Further, published experimental observations of bed voidage in a two-phase FBBR agreed well with the model predictions, with mean deviations of 26.4%, 5.2%, and 9.7% for studies conducted by Mulcahy and Shieh, Ngian and Martin, and Setiadi, respectively, and with a mean deviation of 18.7% for the total published experimental data (297 points) of the above researchers

Recycling hazardous jarosite waste using coal combustion residues

Increase in environmental concern due to improper management of both hazardous and non hazardous wastes released from different industrial process prioritized the necessity for the innovation research. In this context, this paper deals with the immobilization of jarosite waste released from the zinc industry and converting it into a value added product using coal combustion residues (CCRs) through solidification/stabilization (s/s) and sintering process. Experiments were conducted using different ratio of jarosite waste and clay soil with varying concentration of CCRs. The optimized experimental results (using jarosite waste and clay soil ratio of one with 15% CCRs) showed that it is possible to make a composite having desirable mechanical properties such as compressive strength (50-81 kg/cm(2)); water absorption (13-17%); shrinkage (11-32%); and density (1.6-1.8 gm cm(-3)) to use as a construction material. Under solid state sintering process, with the application of CCRs, the mineral phases such as x Fe(3) (SO(4))(2)(OH)(6) [where X=K and NH(4)], 2Fe(2)O(3)SO(3)center dot 5H(2)O, PbSO(4), CaSO(4) in jarosite waste were transformed into a silicate matrices. The leachate studies confirmed that the toxic elements such as Cd, Pb, etc. were immobilized in the jarosite waste composite and meeting the USEPA TCLP toxicity norms for safe utility. The composite product thus developed has showed potential for recycling jarosite waste in construction sector leading to cross sector waste recycling

Characteristics of sludge developed under different loading conditions during UASB reactor start-up and granulation

Sludge characteristics available inside the reactor are of vital importance to maximize advantages of UASB reactor. The organic loading rate and sludge loading rate applied during start-up are among the important parameters to govern the sludge characteristics. Effects of these loading rates on the characteristics of the sludge developed are evaluated in six laboratory scale UASB reactors. The sludge characteristics considered are VSS/SS ratio of the sludge, sludge volume index, specific gravity, settling velocity and metal contents of the sludge developed under different loading rates. The experimental results indicate that, for developing good characteristics sludge, during primary start-up from flocculent inoculum sludge, organic loading rate and sludge loading rate should be in the range of 2.0-4.5 kg COD/m(3) d and 0.1-0.25 kg COD/kg VSS d, respectively (chemical oxygen demand, COD). Proper sludge granulation and higher COD removal efficiency will be achieved by these loading rates. (c) 200

The influence of expert opinions on the selection of wastewater treatment alternatives: A group decision-making approach

The application of multiple-attribute decision-making (MADM) to real life decision problems suggests that avoiding the loss of information through scenario-based approaches and including expert opinions in the decision-making process are two major challenges that require more research efforts. Recently, a wastewater treatment technology selection effort has been made with a 'scenario-based' method of MADM. This paper focuses on a novel approach to incorporate expert opinions into the scenario-based decision-making process, as expert opinions play a major role in the selection of treatment technologies. The sets of criteria and the indicators that are used consist of both qualitative and quantitative criteria. The group decision-making (GDM) approach that is implemented for aggregating expert opinions is based on an analytical hierarchy process (AHP), which is the most widely used MADM method. The pairwise comparison matrices (PCMs) for qualitative criteria are formed based on expert opinions, whereas, a novel approach is proposed for generating PCMs for quantitative criteria. It has been determined that the experts largely prefer natural treatment systems because they are more sustainable in any scenario. However, PCMs based on expert opinions suggest that advanced technologies such as the sequencing batch reactor (SBR) can also be appropriate for a given decision scenario. The proposed GDM approach is a rationalized process that will be more appropriate in realistic scenarios where multiple stakeholders with local and regional societal priorities are involved in the selection of treatment technology. (C) 2013 Elsevier Ltd. All rights reserved