A novel method of sludge pretreatment using the combination of alkalis.

The present study aims to utilise the advantage of higher sludge solubilisation potential of sodium hydroxide (NaOH) and sludge management properties of lime to achieve sludge pretreatment and its subsequent management. The optimum dosage and time required for sludge pretreatment using NaOH was found to be 1.6 g l-1 and 3 hr, respectively. At the optimized condition, lime was added at varying concentration (0.3 to 1.6 g l-1) to study its effect on capillary suction time, soluble chemical oxygen demand (SCOD) release and total phosphorous (TP) removal. A lime dosage of 0.7g l-1 was found to be beneficial for soluble chemical oxygen demand (COD) release. When compared to control, the combination of alkalis (NaOH and lime) reduced the TP and capillary suction time (CST) in the supernatant of the sludge. The TP removal was from 100 to 40 mg l-1 and CST reduction was from 1360 to 350 sec, respectively. The combined alkali pretreatment not only prevent the subsequent TP increase in the effluent, but also decreased the time to filter the sludge, thus makes the digested sludge easier to manage.

A study on the performance of a pilot scale A2/0-MBR system in treating domestic wastewater.

Phosphorus and nitrogen are the important eutrophication nutrients. They were removed in the anaerobic/anoxic/oxic (A2/O) system through biologically. The use of pilot scale A2/O systems with immersed membranes in removing nutrients phosphorus and nitrogen were investigated over a period of 150 days. The A2/O membrane bio reactor (MBR) was operated at a flux of 17 LMH. The designed flux was increased stepwise over a period of one week. The reactor was operated with the mixed liquid suspended solids (MLSS) concentrations in the range of 7000-8000 mg l-1. The phosphorus removal was found to be in the range of 74-84%. The ammonification was completed in the aerobic zone and the ammonia concentration was almost nil. Nitrate concentration in the anoxic zone was found to be in the range of 0.3-1.6 mg l-1 indicating efficient denitrification. The nitrogen removal efficiency of the A2/O-MBR system was in the range of 68 to 75%. The chemical oxygen demand (COD) in the effluent was in the range of 8-5 mgl-1 indicating the efficiency of membrane. During the period of reactor operation transmembrane pressure (TMP) of the reactor increased slowly from 0 to 6 -cmHg over a period of 150 days.

Biomanagement of sago-sludge using an earthworm, Lampito mauritii.

In the present study vermicomposting was carried out at three different concentrations of sago-sludge namely 50, 75 and 100% with an indigenous earthworm, Lampito mauritii for a period of 50 days. The fecundity of earthworm Lampito mauritii was found to be high in 50%. At the end of 50 days composting period. There were about 12 cocoons, 5 juveniles and 2 nonclitellates appeared at 50% sago-sludge concentration. The microbial analysis showed that after 40 days of composting their population stabilized and further increase in composting period did not increase their population size. Chemical analysis of Lampito mauritii worked substrates showed there is a step wise increase of nitrogen and phosphorus. The fold increase of phosphorus and nitrogen were found to be high for sago-sludge undergoing vermicomposting than the control. From the initial value of 1.8, 1.4 and 0.5 mg kg(-1) total nitrogen increased in a stepwise manner and reached a value of 5.8, 3.9 and 2.3 mg kg(-1), respectively for vermicomposting at 50, 75 and 100%. During composting the organic carbon decreased from its initial value of 56, 74 and 107 mg kg(-1) to 15, 25 and 58 mg kg(-1) for vermicomposting and 34, 45 and 72 mg kg(-1) for 50, 70 and 100% control, respectively. The results indicate that 50% and 75% concentration of sludge mixed with bedding material was ideal for the vermicomposting.

Biomanagement of sago-sludge using an earthworm, Eudrilus eugeniae.

Sago, the tapioca starch is manufactured by over 800 small-scale units located in the Salem district, Tamil Nadu, India. During the processing of sago it generates huge quantities of biodegradable solid waste, as crushed tubers. In present study an attempt was made to convert these biodegradable solid sago tubers into value added compost using an exotic earthworm, Eudrilus eugeniae. The experiments were carried out in a plastic tray at various concentrations of sago-sludge (50% 75% and 100%) for a period of 90 days. During the vermicomposting, data were collected on life form (cocoon, non clitellates, clitellates) of earthworm and it was found to be high in 50% followed by 75% and 100% concentrations. Chemical analysis of worked substrates showed a step wise increase of nitrogen and phosphorus. The fold increase of phosphorus and nitrogen were found to be high for sago-sludge undergoing vermicomposting than the control. During the composting period the organic carbon decreased from its initial value of 58, 76 and 107 mg/kg to 21, 24 and 65 mg/kg for 50, 70 and 100%, respectively The microbial analysis showed that after 75 days of composting, their population stabilized and further increase in composting period did not increase their population size. The results indicate that 50% and 75% concentration of sludge mixed with bedding material was ideal for the vermicomposting.

Solid state biomethanation of fruit wastes.

Overtones of fruit wastes accumulate daily in the city of Chennai, India and there is an urgent need to develop, assess and use ecofriendly methods to dispose them. Presently an attempt has been made to study solid state biomethanation of fruit wastes using a laboratory scale anaerobic digester Fruit wastes containing 3%, 4% and 5% solids were used for experimentation. Daily and cumulative production of biogas produced during the study was recorded. Increase in nitrogen, phosphorus and potassium content in the feed was observed during the digestion. During the study the biogas generation increased with increase in total solids. While the gas generation was 0.006 m3/day/m3 of the reactor volume when the solid content was 3% the corresponding values for 4% and 5% solids were 0.27and 0.35 m3 respectively Varying TS 3% to 4% has no effect on fermentation stability and pH remained between 6.8 and 7.4, but an inhibition of methanogenic bacteria was observed for TS 5%. The overall performance of the reactor was depressed by changing feed concentration from 3% to 5%. Experiments with 4% initial solid contend was ideal for solid-state biomethanation.

Treatment of spent wash in anaerobic mesophilic suspended growth reactor (AMSGR).

Approximately 400 KL of spent wash or vinasse per annum is generated at an average COD concentration of 100,000 mg/l, by over 250 distilleries in India. There is an urgent need to develop, assess and use ecofriendly methods for the disposal of this high strength wastewater. Therefore, an attempt was made to investigate a few aspects of anaerobic digestion of spent wash collected from a distillery. The study was carried out in a 4 L laboratory scale anaerobic mesophilic suspended growth reactor. After the successful startup, the organic loading was increased stepwise to assess the performance of the reactor. During the study period, biogas generated was recorded and the maximum gas generated was found to be 16.9 L at an Organic Loading Rate (OLR) of 38 g COD/L. A 500% increase in the Volatile Fatty Acid (VFA) concentration (2150 mg/L) was observed, when the OLR was increased from 38 to 39 g COD/L. During the souring phase the removal of COD, Total Solids (TS) and Volatile Solids (VS) were in the order of 52%, 40% and 46% respectively. The methane content in the biogas varied from 65% to 75%.

Growth of Brassica juncea under chromium stress: influence of siderophores and indole 3 acetic acid producing rhizosphere bacteria.

Plant growth promoting rhizobacterial (PGPR) strains A3 and S32 have been shown to promote the growth of Brassica juncea under chromium stress which has been related to the microbial production of siderophores and indole 3 acetic acid (IAA). The aim of the present study is to evaluate the importance of siderophores and IAA producing PGPR on the growth of Brassica juncea under chromium stress. The production of IAA and siderophores were observed in the strains A3 and S32, respectively. Both PGPR strains promote the growth of Brassica juncea under chromium stress. The maximum growth was observed in plants inoculated with siderophores producing strain 32. Both the bacterial inoculum did not influence the uptake of chromium by plants. The present observation showed that PGPR isolates A3 and S32 are capable of protecting the plants against the inhibitory effects of chromium by producing the siderophores and IAA.

Biomanagement of petrochemical sludge using an exotic earthworm Eudrilus eugineae.

Petrochemical industry have severe problem in disposing effluent and semisolid sludge despite repeated recycling. It requires further treatment prior to disposal of sludge. In recent years biological treatment methods received much attention and considered as an efficient low-cost treatment. One such method is vermiculture treatment The end product of vermicompost is rich in essential micro and macronutrients along with microorganisms in a very simple form. Adding cast, not only improves the soil structure and fertility but also leads to improvement in overall plant growth and thus increase their yield. The present study was carried out to dispose the petrochemical sludge biologically using an exotic earthworm Eudrilus eugineae. The petrochemical sludge at various concentrations 25, 50 and 75% were subjected to vermicomposting treatment for a period of 60 days. During the period of study, data were collected on life form of earthworm and chemical analysis of the sludge before and after treatment. The microbial analysis was carried out fortnightly. The results indicate that 25 and 50% concentration of sludge was ideal for the vermicomposting, whereas the higher concentration inhibits the vermicomposting.