Balancing is the storage and mixing of effluent over a chosen period to smooth out the variances in both volumetric discharge and pollutant strength.
These variances are particularly prevalent in the soft drink industry due to sudden high concentrations of syrup or detergents being discharged.
Balancing facilitates a controlled discharge of an effluent with a more or less constant pollution load.
Balancing is highly recommended even if the effluent is to be discharged to the municipality, since a balanced effluent is much easier to treat.
An alternative to balancing is segregation which is the separating of the different effluent flows into those that require treatment and those that do not.
This may allow for much smaller treatment works due to reduced volumes.
The intermittent or continuous dumping of caustic can cause extremely high pH and inorganic levels.
Effluents of this nature should be neutralised to bring the pH within acceptable limits before discharge into the final effluent sewer.
Neutralisation can be carried out, either as a batch or as a continuous process, using acid addition (hydrochloric or sulphuric) or CO2
Carbon Dioxide is the most convenient reagent for neutralisation in the soft drink industry since CO2 is cheap and readily available on site.
Approximately 1,1kg CO2 is required to neutralise 1,0 kg sodium hydroxide, producing sodium bicarbonate.
Neutralisation plants are available as propriety units and incorporate loop reactors.
Gaseous neutralization performs more economically if the gas is diffused in fine bubbles.
The majority of soft drink manufacturing plants discharge their waste water to municipal systems.
However, with ever increasing effluent tariffs, many plants may consider installing on-site treatment facilities.
The waste water can be treated by conventional biological processes provided the COD: nitrogen: phosphorus ratio is acceptable.
The characteristics of present-day bottling plant waste water make it amenable to anaerobic treatment.
Anaerobic treatment requires less nitrogen and phosphorous supplementation (both of which are deficient in bottling wastes), than the more popular aerobic treatment system.
A high rate anaerobic system has been developed and is now available.
This system requires a lower retention time and occupies much less space than the traditional anaerobic or aerobic treatment plants.
This is particularly relevant since space is often a limiting factor as soft drink plants tend to be located in or near urban areas.
Future developments are likely to include the use of reverse osmosis and ultra filtration techniques to achieve total water reclamation for a plant.
Complete caustic recovery is also feasible using these techniques.
Emergency process liquor discharge/bulk dumping of process liquors
In the event of the emergency discharge of process liquors e.g. syrups or the regular dumping of caustic solutions, the local authority should be notified in advance.
It is recommended that caustic is neutralised by CO2 rather than acids in the event of this type of discharge.
The wastewater from production and filling of mineral waters and soft drinks is pre-treated mechanically by a screen and buffered in an aerated mixing and balancing reactor.
After equalization of flow and load the wastewater is given to the biological reactors where organic substances as sugar and other organic compounds are decreased by biological activity of microorganisms.
The separation of activated sludge takes place inside a funnel-shaped clarification and the sedimented sludge is given back to the biological system by wear-less, high economic air-lift pumps.
The integrated Process essentially contributes the aerobically digestion of sludge and assures a high safety and stabilization in process operation.
Characteristics of Soft Drink Waste Waters:
The wastewater is a heterogeneous mixture of chemicals including sucrose, maltose, lactose, levulose, glucose, fructose etc., artificial sweetener, fruit juice concentrates, flavoring agents (fruit cells, kola bean extract, vanilla, tonka, oil of sassafras), carbon dioxide, bicarbonates, coloring agents (caramel, synthetic dye-stuff), ethylenediaminetetraacetic acid (EDTA), 1,2-propanediol, gum arabic, preservatives (phosphoric acid, tartaric acid, sodium benzoate, citric acid,) and mineral salts used in manufacturing operations (Ghosh and Henry, 1981)
The average Specific Pollution Load (SPL) was found to be 4 kg COD /m3 of soft drink waste waters.
The target for TDS should be set at 5 kg TDS/m3 soft drink for plants with bottle-washers and 1.5 kg TDS/m3 soft drink for plants without bottle-washers.
Prior to balancing or discharge, soft drink effluent should undergo solids removal to prevent labels, can, bottle lids and other solids from entering the effluent stream.
This can be done by using the simple manually cleaned screens or the more sophisticated rotary, vibrating or static wedge wire types.
Recommendations of Use:
Higher hydraulic retention time and higher solid retention time are recommended.
Extended aeration and aerated lagoons are recommended.
Oils, Fats and Grease may be separated first.
OXIFORTE @ 1gm / KL / day in Primary clarifier tank
Flocculants mix of TRIFLOC (Ferric sulphate, Polyaluminum chloride, Chitosan) @ 1gm / 7.5 KL in Primary clarifier Tank.
SDWWTP @ 1 gm /10 KL /day in Aerobic tank along with an addition of OXIORTE @ 1gm / 10 KL / day
Aerator usage may be reduced by 50%
Sludge removal frequency can be improved say from 20 days to 30-40 days.