Feasibility of hydraulic separation in a novel anaerobic-anoxic upflow reactor for biological nutrient removal

ABSTRACT : This contribution deals with a novel anaerobic-anoxic reactor for biological nutrient removal (BNR) from wastewater, termed AnoxAn. In the AnoxAn reactor, the anaerobic and anoxic zones for phosphate removal and denitrification are integrated in a single continuous upflow sludge blanket reactor, aiming at high compactness and efficiency. Its application is envisaged in those cases where retrofitting of existing wastewater treatment plants for BNR, or the construction of new ones, is limited by the available surface area. The environmental conditions are vertically divided up inside the reactor with the anaerobic zone at the bottom and the anoxic zone above. The capability of the AnoxAn configuration to establish two hydraulically separated zones inside the single reactor was assessed by means of hydraulic characterization experiments and model simulations. Residence time distribution (RTD) experiments in clean water were performed in a bench-scale (48.4 L) AnoxAn prototype. The required hydraulic separation between the anaerobic and anoxic zones, as well as adequate mixing in the individual zones, was obtained through selected mixing devices. The observed behaviour was described by a hydraulic model consisting of continuous stirred tank reactors and plug-flow reactors. The impact of the denitrification process in the anoxic zone on the hydraulic separation was subsequently evaluated through model simulations. The desired hydraulic behaviour proved feasible, involving little mixing between the anaerobic and anoxic zones (mixing flowrate 40.2% of influent flowrate) and negligible nitrate concentration in the anaerobic zone (less than 0.1 mgN L-1) when denitrification was considered

Wastewater renovation using constructed soil filter (CSF): A novel approach

Constructed soil filter (CSF) also known as Soil Biotechnology (SBT) is a process for water renovation which makes use of formulated media with culture of soil macro- and microorganisms. CSF combines sedimentation, infiltration and biodegradation processes to remove oxidizable organics and inorganics of wastewater in a single facility. Operating experience shows hydraulic loading in the range of 0.05-0.25 m(3)/m(2) h and organic loading up to 200-680 g/m(2) d. The results show increase in dissolved oxygen levels, COD removal (from 352 mg/l to 20 mg/l); BOD removal (from 211 mg/l to 7.0 mg/l); suspended solids removal (from 293 mg/l to 16 mg/l): turbidity reduction (from 145 NTU to 5.3 NTU): iron (from 5 mg/l to 0.3 mg/l); arsenic (from 500 mu g/l to 10 mu g/l); total coliform and fecal coliform removal (from 145 x 10(5) to 55 CFU/100 mL and 150 x 10(8) to 110 CFU/100 mL respectively), with desired pathogen levels as per WHO standards, i.e. <= 10(3) CFU/100 mL CSF reveals advantages such as low HRT (0.5-2.0 h), low energy requirement (0.04 kW h/m(3)), no pre-treatment, high dissolved oxygen levels in the effluent, no biosludge production, no mechanical aeration and no odor, fish compatible water quality and evergreen ambience. (C) 200

Adsorption of arsenic from aqueous solution on naturally available red soil

In the present study arsenate and arsenite removal from naturally available red soil in and around Western Ghats of Maharashtra near Mumbai has been investigated. The parameters like adsorbent dose, operating pH, contact time, initial arsenite concentration, adsorbent particle size, etc. on the removal of arsenite and arsenate are examined. Kinetic study in centrifuge vessel reveals that uptake of As (III) ions is rapid in the first two hours and slows down thereafter Maximum removal efficiency of As (III) achieved is 98% at an adsorbent dose of 45 g l(-1) with initial As (III) concentration of 1000 mu g l(-1) in batch studies and 95% at 25 g l(-1) absorbent dose under the same conditions. Equilibrium time is almost independent of initial arsenite concentration. Equilibrium studies show that As (III) ions have high affinity towards red soil even at very low concentration of arsenite. In speciation study, about 25% conversion to As (III) from As (III) is observed, with initial As (III) concentration of 1000 mu gl(-1) and at 25 g l(-1) adsorbent dose. The results suggest that red soil could be used as effective filter medium for removal of arsenic from water

Removal of arsenite from water by soil biotechnology

In this paper we present oxidation of As(III) to As(V) by formulated media via natural oxidation in Soil Biotechnology (SBT) and subsequent co-precipitation by ferric chloride. SBT houses an engineered ecology of formulated media containing selected micro and macroorganisms, such as earthworms, and indicator plants. In SBT, fundamental chemical reactions of nature, such as respiration, photosynthesis and mineral weathering, are integrated and synergised together with microbial diversity which is very active in formulated media. It is found that residual arsenic in water via SBT is below 10 ppb. It is also shown that arsenic content on solid iron residue after SBT is 150 mu g/mg of iron