Anaerobic treatment of wastewater

ANAEROBIC TREATMENT OF WASTEWATER

* GROUP NUMBER: 7
* TEAM MEMBERS: VINCENT DE CAMOTTE, TIM DONKERS AND CELIA MARÍA TARDÍO RODRÍGUEZ
* DATE: FOURTH WEEK SEPTEMBER 2011

* SUMARY:
* INTRODUCTION:

Anaerobic wastewater treatment differs from conventional aerobic treatment in that no aeration is applied. The absence of oxygen leads to controlled anaerobic conversions oforganic pollutants to carbon dioxide and methane, the latter of which can be utilised as energy source. The main advantages of anaerobic treatment are the very high loading rates that can be applied (10 to 20 times as high as in conventional activated sludge treatment) and the very low operating costs. Anaerobic treatment often is very cost-effective in reducing discharge levies combined with theproduction of reusable energy in the form of biogas. [1]
In this practical we want to show the inter-dependency of parameters like COD concentration, composition and HRT of influent, of which influence the UASB reactor efficiency in anaerobic treatment wastewater. Also we should learn the performance of a UASB and how it works. We have to make mass balance and we should find the effects that processparameters have on the bacterial conversion processes. At the end we have to compare the results of the UASB reactor to BATCH with the same types and initial concentrations of substrates.
It is important to know what a UASB reactor and BATCH reactor are. UASB reactors (Upflow Anaerobic Sludge Blanket) are a type of tubular bioreactor operating in continuous and upward flow; the tributary entersthe bottom of the reactor, through the entire longitudinal profile, and out of the top. They are anaerobic reactors in which microorganisms are grouped to form biogranules. [2] A batch reactor consists of a tank with an agitator and integral heating/cooling system. These vessels may vary in size from less than 1 litre to more than 15,000 litres. They are usually fabricated in steel, stainlesssteel, glass lined steel, glass or exotic alloy. Liquids and solids are usually charged via connections in the top cover of the reactor. Vapours and gases also discharge through connections in the top. Liquids are usually discharged out of the bottom. [3]

UASB reactor Batch reactor
* MATERIALS AND METHODS
Materials:
We have used an UASB reactor that contained effective liquid volume 0.83L. anaerobic granular sludge 216 g TSS/kg wet sludge and 134 g VSS/kg wet sludge.
Also we have worked with pumps, thermostats, gas meters, batch bottles, caps and Oxi-Top heads (shaker at 30ºC). The artificial substrate in this practical has been: sodium acetate C2. The used influent will be prepared by the practical assistants.
Furthermore we need: nutrient, buffer, trace element solutions,syringes, test tubes, epjes, centrifuge, COD determination kits, volatile fatty acid (VFA) and gas composition determination materials.
Execution:
Before starting our work we have to know something:
* About substrates (Influent): we have to check if 212.6 g of sodium acetate 3H2O (NaC2H3O23H2O) is correct for preparing a stock solution of 100 g COD/L. Also we have to check if 91 g ofgelatine is correct for preparing a stock solution of 100 g COD/L using the general chemical notation for proteins (C4H6.1O1.2N)x
* 100g COD/L ~100gO2L~100g32=3,125 mol O2
The reaction is: C2H3O23H2O+H2O→C2H4O2+7OH-+Na- , we take C2H4O2 because Na is not going to be oxidated and the relation mol with NaC2H3O23H2O is the same so we can work better with this one. The relation with O2 is 1:2 we havegot 3,125 moles of O2 so we need 1,5625 moles of C2H4O2. 1 mol of NaC2H3O23H2O are 136 g and we have got 1,5625 moles so we have got 212,5 g. It is correct.
* In this case we do not have to separate things the only strange thing is N but we have to know how to work with it. It becomes into NH3. We do the same as we have done in the exercise before, now the relation of moles is 1:4 so we need...