Pig

Rendering Wastewater

Although the flows from on site rendering operations are usually typically small in comparison to wastewater from processing areas and yards, this wastewater is usually highly concentrated and requires addressing the overall treatment plant design.

Nitrogen and ammonia levels are particularly high and can often be over 1000mg/L with BOD levels approaching 100,000mg/L at times.

A chemical DAF system dedicated to pre-treating wastewater from the rendering plant can often be beneficial to the overall wastewater treatment plant operations.

Slaughterhouse wastewater

Wastewater from slaughterhouses is heavily loaded with solids, fat, blood, manure, and a variety of organic compounds originating from proteins. The actual composition of the wastewater from each facility depends on the actual production methods employed, but from the point of view of a wastewater treatment designer, there are adequate similarities to enable designs to be made for Greenfield sites.

The main sources of water contamination are from stockyards, slaughtering, paunch handling, carcass washing, rendering, trimming, and general cleaning.

Slaughterhouse wastewater contains a variety of biodegradable organic compounds, mainly consisting of particulate and dissolved fats and proteins. In comparison to many other food processing wastewater, slaughterhouse wastewater is generally considered to be of a high strength in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS) and particularly high in nitrogen and phosphorus. The pH is generally around neutral.

The two most contaminated process streams are related to blood and paunch contents. Blood and meat proteins are the most significant sources of nitrogen in the wastewater and rapidly give rise to ammonical nitrogen as breakdown occurs. Additionally blood (which has a COD of about 400,000 mg/L), if not properly controlled will add considerably to the organic load in the wastewater.

Typical raw wastewater characteristics are shown in the chart below

Primary Treatment

Primary treatment of wastewater from slaughterhouses is a generally considered to be good practice as the bulk of the solids and grease can be quite easily and inexpensively removed which significantly reduces the load on any secondary plant.

Primary treatment methods include one or all of the following:

Fat traps
Screens (please click here for details on the various types of screens available)
Dissolved air flotation (click here for specific details on our range of Hy-DAF systems)
DAF units are still extensively used within the meat processing industry. The effectiveness of a DAF system depends on a number of factors including; whether or not chemicals are dosed and its position within the overall process. Often separate DAF systems are installed to treat the green and the red streams to allow recovery of fat as tallow.

The efficiency of the process for fat removal is reduced if the temperature of the water is too hot. The increase in fat recovery from reducing the wastewater temperature from 40 to 30 degrees C can be up to 50%, so heat exchangers can play a vital part in terms of performance or recovery of fat.

Without chemical treatment on a combined red and green stream, a DAF system will remove 20–30% of the COD/BOD, 30–60% of the SS, and 60–90% of the oil and grease. The percentage reduction increases with an increased load entering the plant.

Chemical treatment can significantly improve the performance of a DAF system. Historically ferric chloride is used to precipitate proteins and polymers used to aid coagulation, however with advances in polymer design, a high dose of polymer can be almost as effective at a considerably lower cost with a further benefit of generating less sludge. BOD reductions of 80% or more can be achieved with a suitable chemical program with over 95% reduction in solids and grease.

Biological Secondary Treatment

Using biological treatment, can treat wastewater to achieve very low levels of organics and nutrients. Aerobic treatment can allow wastewater to discharged to the environment or with tertiary treatment allow for reuse.

Commonly used systems include lagoons, conventional activated sludge systems with advanced aeration , sequencing batch reactors, moving bed bio reactors and membrane bioreactors.

Aerobic biological treatment for the treatment of biodegradable wastes has been used for many years and can be designed to reduce influent BOD by 95% or more. As wastewater form meat processing plants is highly biodegradable, such systems are ideal and quite common practise.

In determining what the most suitable biological process is, a number of factors need to be taken into account. These include; the performance requirements, the land area available, energy costs and efficiency, and waste biomass production.

Of particular note in terms of performance requirements are the increasingly stringent nutrient limits being imposed in all states and territories of Australia. Removing organic material (or BOD) is relatively simple and energy efficient whereas nitrification and denitrification processes require considerably more power.

The type and size of biological system also depends on the upstream treatment methods. Typically due to the cost of operating a biolfial plant, upstream treatment should be optimised for maximum economic performance.

As there are so many variations to biological plant deisgn, we invite you to have a look at our web pages on this topic here and contact us if you require any specific information.

Some typical process diagrams can be found below:

Primary DAF process with chemical addition

Secondary wastewater treatment process using MBR

Secondary wastewater treatment process using MBBR

Secondary wastewater treatment process using SBR

DESIGN CONSTRUCTION OPERATION

Engaging a professional wastewater treatment company to look after the entire wastewater project is a convenient, economical and hassle free option for industry.

Hydroflux Industrial can provide all process design works, manufacture and fabrication, construction and even complete operation of your wastewater treatment plant.

When Hydroflux Industrial provides complete solutions, we can either undertake a contract on a turnkey basis or work together with building services engineers and other construction professionals such as architects, structural engineers and quantity surveyors to ensure that the project is delivered smoothly, without interruption and on time.

BUILD OPERATE TRANSFER (BOT) FINANCING

The Hydroflux Group is able to offer a Build Operate & Transfer (BOT) option for water and wastewater assets in Australia and New Zealand. This innovative partnership arrangement strengthens existing strong bonds between Hydroflux and their customers for the long term.

Hydroflux, represented by a special purpose vehicle dedicated to the project, supplies the design, construction, financing, and operation of the water or wastewater plant. The plant is transferred to the client at the end of the contract, which is generally around 10 years.

Hydroflux also purchase existing water and wastewater plants on a similar basis, which releases cash to our clients for either returning or distributing to investors or for funding other investments in their core business.

The multidisciplinary structure of the Hydroflux group including design, construction, equipment supply and operation makes Hydroflux the ideal BOT water and wastewater partner.

Please contact Hydroflux if would like to explore the option of either acquiring a new water or wastewater facility without capital outlay or would like to free up cash by selling your existing water or wastewater assets.

Download Hydroflux Industrial Meat Industry Brochure

Primary DAF process with chemical addition

Secondary wastewater treatment process using MBR

Secondary wastewater treatment process using MBBR

Secondary wastewater treatment process using SBR