Renu Bhargava

Vermitechnology for sewage sludge recycling.

The present paper is aimed at safe reuse and recycling of sewage sludge (SS) and production of good quality compost using vermicomposting. Three different earthworm species Eiseniafetida (E. fetida), Eudrilus eugeniae (E. eugeniae), Perionyx excavatus (P. excavatus) in individual and combinations were utilized to compare the suitability of worm species for composting of sewage sludge as well as the quality of the end product. The sewage sludge without blending can be directly converted into good quality fertilizer (vermicompost). Vermicomposting resulted in reduction in C/N ratio 25.6 to 6-9, TOC (25%) but increase in electrical conductivity (EC) (47-51%), total nitrogen (TN) (2.4-2.8 times), potassium (45-71%), calcium (49-62%), sodium (62-82%) and total phosphorous (TP) (1.5-1.8 times), which indicated that sewage sludge can be recycled as a good quality fertilizer. The present study also inferred that the application of sewage sludge in the agricultural fields after vermicomposting would not have any adverse effect as the heavy metals (Cu, Mn, Pb and Zn) are now within the permissible limits.

Bioconversion of filter mud using vermicomposting employing two exotic and one local earthworm species.

Three different earthworm species Eisenia fetida, Eudrilus eugeniae and Perionyx excavatus in individual (Monocultures) and combinations (Polycultures) were utilized to compare the suitability of worm species for vermicomposting of filter mud as well as the quality of the end product. The filter mud blended with saw dust can be directly converted into good quality fertilizer (vermicompost). Eight different reactors including three monocultures and four polycultures of E. fetida, E. eugeniae and P. excavatus and one control were used for the experiment. Vermicomposting resulted in significant reduction in C/N ratio, pH, total organic matter (TOC) but increase in electrical conductivity (EC), total nitrogen (TN), total phosphorus (TP) and macronutrients (K, Ca and Na). Oxygen uptake rate (OUR) dropped up to 1.64-1.95 mg/g (volatile solids) VS/day for monoculture reactors and 1.45-1.78 mg/g VS/day for polycultures reactors, respectively, after 45 days of vermicomposting. Cocoon production and the earthworm biomass increased as vermicomposting progressed. On an overall the mono as well as polyculture reactors produced high quality stable compost free from pathogens and no specific differentiation could be inferred between the reactors.

Effect of organic shock loads on a two-stage activated sludge-biofilm reactor.

The effects of short-term organic shock loads on the performance of a laboratory scale two-stage activated sludge (AS)-biofilm reactor working at 6 h HRT and treating medium strength domestic wastewater was studied by increasing the influent chemical oxygen demand (COD) to 2-4 times the normal values. Each shock load was applied for a period of 6 h, after which normal loading conditions were resumed. The maximum effluent COD concentration obtained was 169, 169, 250 and 617 mg/L under the shock loads of 808, 1170, 1358 and 1900 mg COD/L, respectively. The COD removal rate increased with increasing effective OLR. The system recovered quickly from shock loads; recovery time proportional to the magnitude of shock loads. The optimum loading rate of the reactor was found at effective OLR of 170 mg COD/m(3)/h. Shock loads changed the dominant bacterial type in the reactor from Gram-positive rods to Gram-negative oval shaped bacteria.

On site domestic organic waste treatment through vermitechnology using indigenous earthworm species.

In India the exotic epigeic species, Eisenia fetida is mostly used for vermicomposting. The introduction of exotic species into local bio system may affect the indigenous earthworm species population. A comparative study between exotic species (Eisenia fetida) and indigenous species Perionyx sansibaricus and Perionyx excavates was performed to determine the potential of indigenous species of the area vis-à-vis the exotic species for composting of domestic organic waste blended with cattle manure. The results of the study show a significant reduction in initial C/N ratio from 55 to 13 for P. excavates and 15 for P. sansibaricus of the ready product which was within the agronomic acceptable limit ( < 20). The total organic matter reduced by 50% and pH also reduced to be nearer to neutral, but there was an increase in total nitrogen to 102% and total phosphorus increased from the initial concentration of 7.62 g kg−1 up to 13.2 g kg−1. Overall, by employing above indigenous species, domestic organic waste can be directly converted into high-quality hygienic stable fertilizer (vermicompost) which is rich in nitrogen, phosphorus and potassium and free from pathogens.

Pathogen removal during wastewater treatment by vermifiltration

The study was designed to determine the effect of earthworms and the mechanism behind removal of pathogens during wastewater treatment by vermifiltration. The experimental phase continued for 10 weeks, starting after the initial stabilization phase of one week. Significant organic matter degradation and coliform removal were observed during vermifiltration of domestic wastewater. It was observed that vermifilter (VF) reduced biochemical oxygen demand and chemical oxygen demand by 84.8% and 73.9%, respectively. Significant log removal was observed for total coliforms (TC), faecal coliforms (FC), faecal streptococci (FS) and Escherichia coli with a mean log removal value (K) of 2.92, 2.20, 1.85 and 1.68, respectively. The decay rate constant (k) for indicator organisms (TC, FC and FS) was observed to be high as 8.04, 6.59 and 5.55 m day−1, respectively. The population of total heterotrophic bacteria, total fungi and actinomycetes reduced remarkably by 3.14, 1.29 and 2.13 log units, respectively. Antibacterial activity of the isolated microorganisms from VF against gram-positive Staphylococcus aureus (ATCC 29213) and gram-negative E. coli (ATCC 25922) was observed which indicated the existence of a mechanism that may be responsible for pathogen removal during wastewater treatment. This demonstrated the production of antibacterial substance, from the microorganisms associated with earthworms, that causes inhibition of other microbes, specifying the effect of earthworms for pathogen removal. Overall, the present study contributes to the understanding of mechanism for pathogen removal during vermifiltration through antibacterial action of microflora.

A comparative study for pathogen removal using different filter media during vermifiltration.

The present study focuses on the effect of filter media (riverbed gravel, mud balls, coal and glass balls) for the removal of pathogens during vermifiltration of domestic wastewater. This novel study was conducted for the first time on different vermifilters (VFs) with different media, and pathogen removal was extensively investigated for a period of 3 months. Results indicated that vermifilter with riverbed material (VFR) showed maximum biochemical oxygen demand and chemical oxygen demand removal of 76 and 67%, respectively and vermifilter with mud balls (VFM) showed maximum log removal of total coliforms (2.8), fecal coliforms (2.7), fecal streptococci (2.2), Salmonella (2.1) and Escherichia coli (2.1). The area-based bacterial removal rate constant (k) was found in the range of 2.96-6.68 m/d, which is very high in comparison to the reported values. The population of total heterotrophic bacteria and total fungi was found to be 2-log (99%) higher in VFR and VFM, as compared to other media. The growth rate of Eisenia fetida was higher (42% increase in biomass) in glass balls vermifilter (VFG), and also the abrasions on the body wall of earthworms in VFG showed fewer injuries. Overall, the results of the study described the importance and role of each filter medium.

Nitrification kinetics of activated sludge-biofilm system: A mathematical model

Although activated sludge (AS)-biofilm system has many advantages, it lacks in the mathematical concepts for its design. This paper deals with deducing a mathematical model for the simulation of ammonical nitrogen in such systems starting from the basic mass balance equations. Monod kinetic equation and Fickian diffusion principles are coupled to derive the model. The model thus developed is solved numerically and validated with the experimental results obtained on a laboratory scale AS-biofilm system. It is found that the model validated well with the experimental results which was supported by the R(2) value of 0.79, further the statistical analysis between the observed and predicted values for various experimental conditions showed that the model tends to under-predict at high removal efficiency, whilst a slight tendency towards over-prediction at low removal efficiency values. Fractional error plot for the NH(4)(+)-N data sets showed that the difference between observed and predicted values are insignificant at 5% level of probability for NH(4)(+)-N.

Conserving urban lakes for tourism and recreation in developing countries: a case from Chandigarh, India

The Sukhna Lake of Chandigarh city is one of the prominent spots for outdoor recreation and tourism in northern India. In this paper, an attempt has been made to estimate the social benefit–cost ratio of this urban lake conservation project. It has been observed that social benefits completely outweigh the conservation costs incurred on the lake during last ten years. The efforts need to be augmented towards soil and water conservation measures in the lake catchment to make the lake aesthetically more appealing by way of utilising excess revenue earned over the conservation costs. Construction activities need to be banned in the catchment area and waste water needs to be prevented from entering the lake from catchment villages. All these measures will help not only in improving the water quality but also in increasing the recreational and aesthetic value of the lake resulting in enhanced tourist arrival and revenue.

Design of multistage activated sludge-biofilm reactors: a rational approach

This paper outlines a mathematical model developed for steady-state multistage completely mixed hybrid reactors, starting from basic mass balance expressions for the system and Ficks theory for diffusion of substrate into the biofilm. The model being complex, a design procedure has been proposed that uses predefined effluent quality profile across the system and results in an accurate and optimum design of the system for a desired degree of treatment. Using reported values of kinetic parameters from literature, it has been concluded that the proposed computationally efficient procedure can be successfully used for the design and control of these reactors.

Effect of nutrient addition on performance of animal waste fed stabilization ponds

Abstract Waste stabilization ponds have established as the most economical, convenient and complete treatment for domestic and industrial waste. Their use in the field of animal waste treatment, is however a recent one. The studies conducted for the evaluation of algal growth promoting substances, specifically Nitrogen, Phosphorus, Magnesium and Boron revealed that the controlled dosages of these nutrients are helpful in increased production and increased efficiency of treatment.