Other solid wastes include Broken glass from packaging Paper and pulp (label sludge) from bottle washer Paper, plastic and metal from auxiliary material Waste oil & grease from Machinery.The environmental issues associated with breweries are the discharge of very large quantities of waste water with high concentration of organic matter, CO2 emissions from fermentation and improper handling and disposal of solid residues. Odors can also be a major problem for breweries located close to residential areas.Generally effluent generated from the brewery operations is represented schematically in Fig.
17 below: Fig.17: General process flow diagram for Breweries, showing input and Waste output streamsBrewery Waste WaterBrewery waste water generally has the following characteristics: They are highly biodegradable It shows high variability in suspended solids, COD & pH due to continuous discharges of the brewery’s different sections Usually contains a slight surplus of phosphorus and nitrogen, The temperature generally averages around 25oC, although higher or lower temperatures are possible pH fluctuates depending on the product used for cleaning typical values of COD, BOD & SS of brewery wastewater are show in Table 3 below: Table 3: Typical values of COD, BOD, SS, Temperature (IBD, 2008).
Treatment TechnologiesMost Breweries discharge waste water directly to municipal sewerage systems after some minor pretreatment generally pH adjustment in a balancing tank. They however pay charges to discharge effluent to the municipal sewer based on volume and total load of COD &SS.If the brewery does not discharge to the municipal sewer, primary, secondary and tertiary treatment of the effluent is required.Primary treatment: this is the first stage of contaminants removal in the waste water treatment plant through screening and settling process which can remove as high as 40-50% of contaminants. Primary treatment facilities include pH adjustment, roughing screens, grit-settling chambers and a clarifier. Sludge from the clarifier is dewatered and disposed of via incineration or to approved landfill sites. Modern plants recover and reuse the water. Vapors are sent to the boiler and burned. There is generally need for physical separation of SS and pH correction. Cleaning water from CIP and rinsing contribute the largest volume. This stream is usually caustic, high COD and sometimes contains oxidizing agents. Thus, the waste water must be held in a balancing tank to allow the oxidizing agents time to react and prevent them from inhibiting biological processes.If the streams contain metal ions that require removal, the metals are precipitated and separated out prior to pH adjustment. This is achieved by using a self-buffering coagulant that give rise to readily filterable sludge to produce waste cake. pH may be corrected using acids. SS must be removed by gravity settlement in tanks or dissolved air flotation (DAF) plant. Biological oxidation or anaerobic digestion can then be used to treat the supernatant.Secondary treatment: reduces SS through biological cleansing, to remove 85-95% of contaminants. It is usually a 2-stage process which includes anaerobic treatment whereby organic matter is converted to methane and CO2 and aerobic treatment whereby the organic matter is converted to CO2 and biomass. It is possible to use a combination of the 2 methods to achieve the required degree of treatment.a. Anaerobic treatment: this means degradation of waste water in the absence of oxygen. Microorganisms degrade organic matter. The digested products are subsequently converted into hydrogen, CO2 and methane. Different micro-organisms are involved in this process. This results in organic material being converted predominantly into biogas which can be used as fuel reducing energy purchases. b. Aerobic treatment: several types exist but most widely used in breweries is the activated sludge system. It consists of pre-treatment step to remove large particulate substances by screening, aeration basin, sedimentation basin and a sludge handling facility. The biomass or sludge absorbs the organic matter, increasing the cell material resulting in more sludge produced. A large part (40-80) % of the dissolved will be converted into solid material that has to be disposed of. The rest of the BOD provides energy for cell maintenance and escapes into the atmosphere as CO2. The biochemical reactions that takes place in this stage are: Biomass Destruction phase. This is the stage in which the bacteria/bugs (biomass eats itself up through protoplasmic oxidation. Under the right conditions, the bacteria utilize the DO in the waste water to degrade the organic compounds into CO2, water and energy, cleaning the water of harmful substances in the process. Aeration of the sludge is a very energy intensive process and accounts for over half of the waste water treatment plant energy cost (Penn, 2015, pp.14-15). Conventional laboratory methods of determining DO in the waste water using Winkler titration methods and portable handheld meters give reasonable reliable results which are only indication of the DO levels at a given period under certain conditions. Continuous measurement of DO using online DO measuring system offers the best way of ensuring the right conditions for maximum aeration efficiency. C5H5NO2 + 5O2 4CO2 + H2O + NH4HCO3(Biomass) (Ammonium bicarbonates increases the pH)The ammonia is toxic by reducing the alkalinity to the microbes (biomass) and gives pungent odor, hence, must be promptly removed; this is achieved in the nitrification phase. Nitrification phase: Involves the removal of ammonia produced in the biomass phase by nitrifying bacteria. NH3 +2O2 H2O + H+ + NO3 The nitric acid drops the pH of the medium which if left untreated will be toxic to the biomass. Denitrification phase: final biological process for the neutralization of nitric acid done in the absence of oxygen.4NO3 NH3 +HCO3- +N2 (alkalinity)Combined Anaerobic-Aerobic treatment is also possible based on resource constraints. For instance, if the brewery is in a residential neighborhood which requires odorless treatment or if the brewery has limited building area. The combined treatment requires less oxygen, and results in lower energy cost. In addition to a relatively small building area, and near odorless treatment, the process is relatively fast.Tertiary treatment: of waste water includes filtration and disinfection which effectively removes >99.999% contaminants.Most analysis like pH, COD, BOD, SS, TDS etc. are done on the waste water treatment plant are either done off-line or in the Laboratory. Analysis like BOD requires a minimum of 5 days incubation in the dark at 20oC hence these results cannot not be used for any process control. Other analysis like pH are done by taking grab samples for periodic tests. Since the flow of waste water is almost a continuous process, the need to have in-line meters for analytical measurement is vital. A schematic representation of a waste water treatment plant with some inline measurement displayed in Fig.18. Fig.18: Waste Water Treatment Plant with in-line Monitoring meters.pH and temperature adjustment are crucial to prevent killing of the microbes in the sludge digester. It is strongly advised to install a CO2 monitoring meter around the Sludge digestion tank for safety reasons. The final effluent must be free of microbes by chlorination or UV treatment before discharge to prevent foul smell into the environment.4.3 Steam ProductionProduction of steam in the Brewery is the most energy intensive process which involves a combination of water treatment and heating. Hence, every step must be taken to reduce the energy requirements. Limestone present in water can cause calcium scaling which leads to reduced heat transfer efficiencies. Thus, it is necessary to treat boiler feed water since hard water leads to a build-up of scale with loss in boiler efficiency. Methods commonly used to treat boiler feed water vary with type of boiler usually the choice is between chemical treatment with lime and ion exchange. The process water must be treated (softened) to replace certain ions (e.g. Magnesium and Calcium) that are responsible for causing water hardness (temporary & permanent) with Sodium ions. The water pH must also be adjusted and checked; the dissolved oxygen concentration of the boiler feed water from the Hot well must also be checked to ensure it is within specification. These process steps are important to prevent corrosion of the steam generating equipment that impedes effective heat exchange leading to high energy consumption. In most Breweries, analyses on the steam generation plant is mainly done in the Laboratory which usually requires extra staff(s) responsible for this. Some of these analyses are not routinely done hence affecting their effectiveness in process control (see appendix 3 on Steam Boiler-Sampling plan).A schematic diagram of a typical steam generation system with proposed in-line monitoring equipment is shown in Fig.19 below: Fig.19: Steam generation system with in-line monitors4.4 Cleaning of Vessels and pipingsMicrobial contamination due to inadequate cleaning of vessels, pipe works, and equipment can adversely compromise all good efforts made by the Brewer in choosing the best quality raw materials for brewing and ensuring accuracy in process analysis for process control. Hence, adequate cleaning of all process vessels, pipings and equipment are of extreme importance. This can be achieved in one of four ways: Manual Cleaning: The process steps followed here are: pre-rinsing with potable water to sufficiently remove loose organic soils (dirt). This is followed by detergent use at the correct concentration and scrubbing. Extreme care must be taken to prevent scratching of the surface during scrubbing. The cleaned surface is thoroughly rinsed with potable water. High Pressure Cleaning: This technique combines high pressure, high temperature and detergents. It allows effective cleaning of the surface that are generally difficult to access. Cleaning at high pressure and high temperature minimizes detergent usages hence, low environmental foot print. Foam Cleaning: The cleaning solution is diluted with air. Small quantities of the detergent solutions at high concentrations are used. The generated foam adheres to the dirt, emulsifies and loosen it which are easily removed by rinsing with water. Cleaning in Place (CIP): This system allows vessels, piping, valves and other ancillary equipment to be cleaned without dismantling all or part of the installation. The surfaces are exposed to controlled conditions where detergents act on the surface to remove the soil and sanitize it. The last 3 systems described above can be complimented with the incorporation of spray systems. Spray Systems: Here, the choice of spray balls or rotating spray cleaners is a major factor in the effectiveness of the CIP system. Spray balls continuously shower the entire surface with the CIP pump is operational directing the impact of the fluid on the area where most of the soil is located. The fluid runs down the side walls of the vessel in a continuous curtain contributing to the chemical effect, timing and temperature to assure a clean surface. There are several different kinds of spray balls, the most common are:‚§ Fixed spray balls with multiple holes adequate to cover the entire surface of the vessel.‚§ Rotating spray ballsBoth types of spray balls require high pressure to direct the fluid onto the surface of the vessel which creates an impact effect at the point of contact. The fluid flows down the rest of the surface cleaning it on it way.VesselsThe effectiveness of CIP over the entire vessel surface is determined by the following factors: Flow rate- this should be high enough (high pressure) to assure cleaning by mechanical action. Concentration of detergents- adequate to remove the target soil and not destroy the vessel surface (chemical action) Contact time- sufficient contact time to ensure wetting and dissolution of the soil. Temperature- suitable to allow optimum detergent performanceThe spray systems are most effective in areas where the cleaning fluid impinges on the surface. The top area surface, where the greatest impingement occurs is always the cleanest provided there is adequate pressure and the holes of the spray balls are unblocked. The middle part of the vessel tends to be less clean. The bottom of the vessels is the least clean as the chemical effectiveness is at lowest due to lower detergent temperatures as the CIP liquid flows down the vessel walls. If the vessels are not well evacuated of CO2, the caustic concentration is neutralized further reducing the cleaning efficiency. To prevent this problem, it is strongly advised to properly evacuate the vessel and install an in-line conductivity meter to measure the concentration of detergents. Process vesselFig.20: Areas of vessel cleanabilityFor effective vessel CIP, the following in-line devices must be installed: Low level probe- this probe must be installed at the outlet of the tank to ensure effective sequencing of the CIP pump and to prevent filling of the tank with product on top of detergent chemicals. The flow rates specified for the spray devices must be checked to conform with standards to ensure cleaning efficiency. This can be done with in-line flow meters. The pressure of the applied CIP solution must be checked with in-line pressure monitor The temperature of the CIP solution before and after application must also be checked with in-line temperature sensors. To conserve water and energy and enhance cleaning efficiency, it is strongly encouraged to install an in-line turbidity meter to measure the turbidity of the return solution to prevent fouling of the CIP storage tank.A classic Vessel Installation that could support in-line measures for both hot and cold CIP is displayed in figure 21 below: Fig.21: Vessel CIP (Institute of Brewing & Distilling, 2009)Pipes: these must be cleaned with hot detergents separately from vessel cleaning. Among other issues like product quality and consistency, one of the most important issues we seek to address in the Brewery by substituting Laboratory analysis with in line analytical process monitors is time. To make a justification for this investment, we first need to know how much time is utilized waiting for Laboratory results.