Unit 9 -Effluent

Question 1

Define effluent

Answer 1

Effluent is defined as the liquid flowing from a process. In the case of a distillery, this is our wastewater.

Question 2

What are the components of a typical distillery effluent?

Answer 2

Waste (wash and lees residues) from fermentation activities

Raw material or product residues removed from sieves or filters

CIP rinse water

Used (dirty) detergent and sanitiser

Environmental waste from general cleaning

Product waste from tank rinses

Question 3

What isn’t effluent?

Answer 3

Spent or dark grains
Pot ale or lees
Hazardous chemicals
Waste solvents, fuel, and paint
Wash and heads and tails
Spent oil and grease
Special cleaning chemicals
Biohazard waste (lab/sanitary/human)

Question 4

What are the key effluent parameters that we can measure?

Answer 4

Volume (also called hydraulic volume)

Suspended solids - solids are harder to treat & often require separate treatment steps

COD (chemical oxygen demand) measures the theoretical amount of oxygen required to break down (oxidise) biological matter in the effluent. Can use sulphuric acid and potassium to test.

BOD (biological oxygen demand) measures the amount of oxygen that is required by micro-organisms to digest the most available nutrients present in the effluent. Measured over a 5 day period.

pH -measure of the acidity or alkalinity of the effluent. Must be close to neutral (pH of 7).

Temperature - should typically be <20C if it is to be released into watercourses.

High temp effluent must be blended and or chilled to achieve a decrease in temperature.

Question 5

What are spot samples vs composite samples?

Answer 5

Spot samples - Taken at the point in time

Composite Samples - taken every few minutes using an autosampler and combined to provide an average across a period of time (typically 24 hrs)

Question 6

How can we target effluent loading?

Answer 6

Collecting last runnings from spent grains or draff, which can contain high-suspended solids and a high COD and BOD. We can reuse last runnings collected into a weak wort vessel for use in the next mash.

Wort cooling water can contribute to high volumes and temperatures. We can recover and reuse it for other purposes.

Water and chemicals for plant cleaning generally go straight to drain. They can contribute to high volume, pH and COD. However, we can recycle final rinses and detergents.

Pot ale has a very high BOD, so care is needed to ensure it does not go to drain but instead into a valuable co-product, such as dark grains or pot ale syrup.

Question 7

How can we reduce the volume of effluent we produce?

Answer 7

Use CIP final rinse water as pre-rinse

Limit washdown hose use (use squeegees)

Use low flow, high pressure rotary CIP heads

Question 8

what is the traditional method of treating effluent?

Answer 8

via facultative lagoons - resemble vast, shallow ponds, where microbes digest the BOD in effluent.

or low-rate trickling filters - are large vessels filled with rough stones, over which the effluent trickles. Microbes on these stones digest and remove the BOD from the effluent.

Both require large amounts of space and take a long time to treat the wastewater effectively. Used at municipal plants

Question 9

Describe primary treatment of effluent

Answer 9

deals with the pH and suspended solids using a series of screens, settling tanks, and clarifiers, which remove the solid and particulate matter as sludge

removes 40-50% of the loading

Question 10

Describe secondary treatment

Answer 10

deals with the BOD/COD and uses anaerobic or aerobic treatments

Question 11

Describe tertiary treatment

Answer 11

the water can be discharged to a watercourse or be recycled back into the distillery. Even though this water is completely safe, it is unlikely that we will reuse it as product water, as people generally do not like the thought of consuming spirits that has been made from waste.

Question 12

What is the typical consent limits?

Answer 12

Maximum volume: 10,000 L per 24 h

Maximum suspended solids: 500 mg/L

COD: 800 kg per 24 h period

pH range: 6-10

Maximum temperature: 40°C

Question 13

Describe secondary treatment

Answer 13

Deals with the BOD/COD and uses aerobic treatments
Removes 85-95%

Question 14

What is used in primary treatment?

Answer 14

A balance tank - they’re designed to ensure that any subsequent treatment equipment receives an even flow of effluent.
Generally designed to hold around 12 hours of effluent

Question 15

After the balance tank, how are settleable solids removed?

Answer 15

by gravity, using settling tanks or tilted lamella plate
Flocculants or coagulants are often added to effluent and make the solids easier to remove.
Another common method used is dissolved air flotation (DAF). In a DAF plant, millions of tiny air bubbles stick to the coagulated solids, float to the surface, and are then skimmed off - known as supernatant

Question 16

What happens to the sludge?

Answer 16

the sludge (the precipitate) from the screens and pre-clarifiers can be further de-watered, reducing its volume even more. It is then either incinerated or sent to landfill
It is often added to the sludge produced from any aerobic/anaerobic treatments.

Question 17

What are the two secondary treatments?

Answer 17

anaerobic and aerobic

Question 18

Describe anaerobic treatment

Answer 18

Anaerobic treatment means that the breakdown of the organic compounds, such as carbohydrates, proteins, and lipids, is achieved via anaerobic bacteria in the absence of oxygen.
A key benefit of anaerobic digestion is that it forms ample biogas and minimal biomass. The biogas can be used as a fuel for steam raising, or to run a gas engine powering a generator to make electricity.

Question 19

Describe aerobic treatment

Answer 19

The activated sludge system is the most common type of aerobic treatment system. Other types include the oxidation bed, the rotating disc contactor, and the fluid bed reactor. The activated sludge system consists of an aeration basin leading to a sedimentation basin, and then finally a sludge discharge facility.

Typically, 40-80% of dissolved organic material is converted into organic sludge