October 18, 2023 posted in Design and Engineering, Food and Beverage Plants, Planning
Water is becoming a scarce resource in many locations. Whether in an existing or a new food/beverage plant, water supply and wastewater disposal now may require new approaches for a variety of reasons, including:
Water supply, wastewater treatment, and disposal are critical issues that must be addressed at the earliest stages of project planning and new plant site selection.
Food processors are required to use potable water for the following uses:
Food processors are required to obtain potable water from an approved public supply. Well water and treated surface water may be used as an option, but only when it meets the same standards as “city water.” Where it is available to processors, potable water from an approved public water supply is often the best choice since on-site sources must be reliably treated (chlorination or more) and sampled/analyzed/reported to prove potability, often at an expense greater than the purchase of water from the local public supply.
Supplies of potable water are not always suitable for product incorporation. Municipal Water treatment technology presently in use is intended for delivering a safe product to residences, and certain water constituents may be present that are safe but could impair product quality or processing efficiency. Supplies need to be analyzed to ensure that parameters important for product formulation can be met. Water with excessive hardness, highly soluble silica, salt, dissolved iron, or manganese, and trace non-toxic organics such as tannins could be a problem, and special treatment may be required to meet product quality standards.
Processors must purchase potable water and then pay for its treatment and disposal. These costs are rising, and the best and often only cost control measure is to have and implement a serious water conservation plan. In almost all cases, preventing waste entry into the wastewater system will be more cost-effective than removing it after it is introduced into the wastewater stream. Process improvements and capturing high-strength waste at the source often can greatly reduce the wastewater burden. Developing modern sanitation procedures can reduce water and chemical consumption, reducing waste loads. It is vital to develop water demand projections that are realistic and based on processing requirements. Estimates of water demand that are based on historical records could be unreasonably high if water conservation programs are not already in place. A survey of current water usage and analysis can be very useful in identifying wasteful practices and designed inefficiencies. Adding water metering and incorporating water use into the cost of production can stimulate the careful utilization of this valuable resource. Water conservation should be a point of focus in planning and designing expansions and new facilities.
Sanitary Wastewater is generated in toilets, hand-washing stations, kitchens, break areas, laboratories, and possibly others. Current Worldwide Food Safety guidelines prohibit combining sanitary and processed wastewater in many situations. Making provisions to handle this wastewater separately from processed wastewater is prudent.
At the present time, it is difficult and costly but not impossible to get approval to treat and reuse wastewater for food processing operations. A better option is to consider the treatment of food process wastewater for reuse in on-site utility systems, landscape irrigation, or groundwater replenishment.
Certain locations (Los Angeles County, Mobile County, Alabama, and others) provide and mandate the use of public industrial wastewater collection sewers for treatment at publicly owned treatment works. This water, after treatment, is available for distribution and subsequent re-use. Identifying opportunities for water reuse at the earliest moment in project planning is essential.
There are several factors to consider before choosing a course of action for treating and disposing process wastewater.
Know your waste: It is essential to properly characterize the raw (untreated) wastewater. Daily flow profiles and waste parameters for a similar operation should be collected along with production data from when the data was obtained. Where real data is unavailable from another similar operation, a literature search, and some math modeling must be done to synthesize the waste flow characteristics. These characteristics need to be matched with a definition of processing operations throughput to be completely useful.
Know the Rules: The rules and requirements can vary widely by location and choice of treatment options below. Meetings with the authorities having jurisdiction are essential to collect written regulations, guidance, and application forms.
If discharge to a Municipal Sewer and Publicly Operated Treatment Works (POTW) is anticipated, then a copy of the current Industrial Sewer Use Ordinance must be obtained and studied along with prevailing rates for tap fees, flow, and surcharges. Meetings will be necessary to discuss flows, waste loads, the Municipality’s capabilities, and any peculiar situations.
If discharge to a receiving stream or land application is anticipated, then a meeting with the State Environmental Agency’s regional permit coordinator will be necessary to determine the exact nature of requirements for the proposed operation.
Look for recoverable materials: Processing material balances should be updated to identify all waste and by-product flows. Then, it is appropriate to look for materials with economic value. It may be possible to screen certain waste streams to collect materials sent out as animal feed or install grease traps to recover oil/grease to send out to bio-diesel refiners or renderers. Also, some large flows containing high sugars could be anaerobically digested for methane recovery. All such opportunities should be cataloged and evaluated for their impact on decision-making.
Consider all Disposal options: Various options are available for treating and disposing of process wastewater.
Direct Discharge to City Sewer: Some Municipalities are set up to handle industrial wastewater discharges with only minimum treatment by the discharger. The minimum treatment requirements usually call for removing gross solids by screening, preventing very low and high pH, and removing freely floating greases and oils. Direct discharge without pre-treatment into a municipal sewer system presents the greatest risk of pollution violations, which may trigger both state and federal (EPA) fines and sanctions. The direct discharge will also bring increased surcharges by the municipality for high-strength waste(s), and the facility will have little or no control over future sewer surcharge rate increases by the governing municipality. While this option has the lowest initial capital cost, ongoing costs may be high, and comparison with other alternatives may be prudent. Prior discussions with the Municipality are necessary.
Pre-Treatment Before Discharge to City Sewer: Most municipalities pay close attention to what goes into their public sewer systems and require monitoring, analysis, and reporting of treatment results. The municipality will normally set two levels for important contaminants. Below the first level, there are no surcharges. Above the second level, discharges are prohibited, and service can be discontinued and fines levied. Between the first and second levels, surcharges are levied to cover the municipality’s cost of treatment of the contaminants. Pre-treatment by the facility can often significantly reduce the surcharges for excess contaminants. The use of this option will mean the continuous operation and maintenance of these systems.
In most cases, pre-treatment may result in residual solids (sludges), which must also be disposed of. By utilizing pre-treatment, facilities can often offset the cost of installing and operating these systems by reducing the cost of municipal sewer surcharges. While the municipality may prefer this option, they may sometimes lack the hydraulic or oxygen capacity to handle the pretreated wastewater. It is essential to meet with the Municipality after collecting waste characterization and flow data and before deciding to select this option.
On-Site Treatment Prior to Surface Water Discharge (NPDES Permit): At some sites, processing plants may be able to treat and discharge directly into a surface water source, such as a stream or river. While it may be convenient, this will require a higher level of treatment when compared to that of either direct discharge or pre-treatment. This option is almost always the least desirable of those available. The only situation that should lead a facility to consider on-site treatment for discharge to surface waters is a lack of access or capacity in the municipal treatment plant. Compared with the previous options, this one typically has the highest capital, operation, maintenance, and permit administration costs and the greatest environmental risk. Before deciding to implement an on-site, treatment-to-surface-water option, consider the available site data and the time and costs that may be associated with completing a permit process, which can be evaluated early in a project’s “due diligence” phase.
On-Site Treatment Before On-site Disposal: At some sites, processing plants may be able to treat and dispose of treated wastewater on the facility property without having any discharge to a stream or sewer. After treatment, the effluent would be applied to cropland or tree farms by spraying or sub-surface application. In cold or very rainy climates, storage ponds may be required to hold effluent during inclement weather. Additional suitable land will be required for this option, The only situations that should lead a facility to consider on-site treatment and on-site disposal are either a lack of access to or a lack of capacity in the municipal treatment plant and either no access to a receiving stream or exceedingly high receiving stream treatment standards. When compared with the other options, this one will typically have capital, operation, and maintenance costs, like the NPDES Permit option. In some jurisdictions, this option is not available under prevailing laws. In certain physical situations, subsurface geology is inappropriate, and such an option is not permittable.
Sludge & Solids Disposal: There will be some amount of solid or slurry material to be disposed of off-site. If the material has a low enough water content, it may be suitable for landfill disposal. Occasionally, additional investment in dewatering equipment can make landfilling feasible. If the quantities of sludge or solids are very large, other options for resource recovery may be feasible (composting, energy recovery) and should be evaluated. Also, these may be used in the vicinity for certain types of solid materials compatible with local operations (ethanol plants, cattle or swine feeding, rendering).
Sampling/Analysis/Reporting: In every case, the effluent must be sampled periodically, analyzed, and reported to the permitting authority. The cost of this activity is not insignificant, and if the frequency of required sampling is high, investment in lab capability and certification on-site may be justified.
Select the proper level of treatment: Depending on the downstream conditions, more or less treatment may be required. A brief description of the level of treatment options follows.
Preliminary Treatment: Preliminary treatment processes are utilized to prepare initial plant effluent for further treatment. These can include:
A plant can reduce the quantity of un-dissolved solids using separation processes. Initial solids reduction can reduce the need for larger-sized downstream processing and larger power requirements and have fewer maintenance requirements. These primary treatment processes may include:
Secondary Treatment: Secondary treatment involves a biological or “living” treatment using microorganisms that remove wastewater contaminants beyond preliminary or primary treatment. Regulations typically require these processes to discharge any treated wastewater into a surface water system. These types of processes are typically more energy-intensive than either preliminary or primary treatment methods.
Tertiary Treatment: Tertiary treatment processes follow primary and secondary processes and produce a high-quality effluent, essentially “polishing” the treated wastewater to the point where the final effluent will contain very small concentrations of contaminants. These processes can include activated carbon absorption, filtration of suspended solids, stripping of dissolved gases, and ion exchange to remove ionized organics and inorganics. While a tertiary process may not be required, when it is required, the type will be dictated by wastewater characteristics, effluent quality, and the receiving stream utilization.
Sludge Handling and Disposal: All treatment processes, except neutralization and flow equalization, produce a solids by-product. The consistency of these solids can range from those containing very little water to mostly water (98%-99%). Most treatment processes will produce solids continuously, which in liquid form can require substantial space to store until disposal. Increasing solids concentration (reducing the amount of water) can substantially reduce the storage requirements for solids. Though an additional initial cost, dewatering and sludge-thickening mechanical systems can more than pay for themselves over time in reduced solids and storage costs. Although increased solids concentration will reduce sludge storage requirements, all plants must ultimately dispose of waste products. This holds true for both processing facilities and the municipal disposal facility. Ultimate disposal includes land application, landfilling, or incineration. The most easily implemented and desirable alternative is to arrange for contract hauling to remove the sludge, making the hauler responsible for both appropriate subsequent treatment and disposal.
Select Appropriate Technology and Consultants: There is an array of proven and commercially available technologies for each disposal option above.
It would be very rare to find food processing wastewater that has not been successfully treated by a small group of special food wastewater equipment companies. Contacting these firms when flow and waste strength data is available can produce some quick concept development and preliminary budgets with minimal effort. The following technologies are examples of processes that have been proven and are available in durable and easy-to-clean equipment.
Dissolved Air Flotation (DAF) systems for removal of emulsions and very fine particulate solids Anaerobic digesters for high BOD wastewater treatment and methane production Sequential Batch Reactors for biological treatment of small volume high strength flows modular package plants incorporating the above and other technologies.
The local Civil Engineer can be very valuable in coordinating permit applications and site development for treatment works. However, he often lacks familiarity with the appropriate technology and normally would not be involved in developing treatment schemes and equipment selection. In some instances, using a local Civil Engineer for processing wastewater treatment can result in economic overkill when compared with specialized equipment suppliers.
Special in-state consulting engineers will be needed to develop schemes, budgets, and permit applications for land applications. These engineers will have the requisite local geotechnical and permitting procedure knowledge to determine feasibility and follow through.
Municipal Sewer and Treatment Authority response: Often, the Municipality is more than willing to expand its system to handle new demand. However, the time required for them to plan, permit, fund, design, and build the necessary services can be years rather than months.
Flow Equalization: There are occasions when the Municipal sewers or lift stations cannot handle flows from the pre-treatment plant during daylight hours but will be able to do so after midnight. In this case, flow equalization storage tanks can eliminate a serious problem.
Contingency Planning Spills/Upsets: Every day is not a good day. Planning needs to consider controlling infrequent and worst-case situations that could result in legal or technical problems at the Municipal Treatment plant.
It is incredible how the simple element of water can create a tremendous need for engineering expertise. Contact us today to put our know-how to work for you.