Sewage Sludge Processing and Drying;
One of the biggest factors that increase the treatment plant operating costs is the disposal of sewage sludge.
As in each waste, reduction the amount of sewage sludge at source and minimising the disposal cost is the greatest request of all company.
Choosing of the technology that produces less sewage sludge is the issue that should be examined and the disposal of the sludge should be made as a priority at the source.
Constitutionally firstly, the ways to of sewage sludge should be searched to turn into economic value of sewage sludge and the technology to be applied should be chosen according to feasibility. The sewage sludge can have economic value according to the contents described below:
Agriculture usage (compost, manure, etc.)
Usage as soil conditioner (in sickle land, non-agricultural use of land sickle)
Usage as cover material (surface soil in the landfill site)
Usage as filler (filling soil in road construction and civil works)
Usage as an additional fuel (such as cement factories)
Considering the project budget and feasibility, Arbiogaz adopt and apply technologies giving below for sludge reduction.
Organic matters in sewage sludge tend to return final products as CO2 and H2O molecules. Organic matters will be activated to return the final product as long as in suitable environment. If oxygen is present, the process occurs with the aerobic reaction. The anaerobic reaction occurs in the absence of the oxygen. Intermediate products occurs in processes according to presence of oxygen are different. During the final disposal of sewage sludge, off odor molecules prevent the formation of product as H2S, CH4. So, there should be no biological activity. This requires completion or termination of biological activities with applicable processes in treatment plants units. After biological activity of sludge is finished, finally become stabile and does not give undesirable products. We refer to this process as stabilization.
Excess sludge coming from biological and chemical units of treatment plant such as preliminary settling, final settling, thickening, must be removed from the system. Solid matter contents in the sludge-fluid vary around 0.5-2%. So, 0,5-2 unit solid matters are found in 100 unit excess sludge
This sludge, waste of treatment plant should be removed from the plant. However, to remove the sludge described above from the treatment plant would be a very expensive cost. Therefore, reducing the volume and practically taking the disposal cost into possible limits are aimed. It is necessary to get rid of the water in the sludge as possible. For this purpose, dewatering processes have been developed.
Mechanical dewatering process is the leading. These methods are;
Pressure-based machines (belt presses, filter presses, etc...)
Centrifugal force based machines (decanters)
Solar radiation based methods (drying beds, solar drying greenhouses)
By this traditional methods, sludge with 0.5-2 % solid become sludge cake contains 16-25 % solids. Approximately half of the free water trapped between the sludge flock are removed by this equipments.
Thus, sludge cake is a product that is easy and possible to transport but not easy to storage.
It can be considered an “intermediate product” for final disposal.
Our company is able to offer different solutions using a variety of processes for solid waste (organic) removal which becomes important nowadays. Composting process is being implemented by our company with the best technology. Conversion to organic fertilizer of decomposed vegetable, animal waste or organic fraction separated from solid waste landfill in moist-oxygenated environment is called compositing. In compost and recycling plants, compost, which is soil corrective and has high organic value and ability to hold water, is produced from organic domestic wastes passing through the physical and chemical processes such as reaction with sufficient moisture, heat and air by microorganisms.
Compost can be obtained in different shapes and by using different equipment. Similar to the natural environment, vegetable and animal organic wastes are exposed to aerobic degradation which will not allow anaerobic decomposition odor. Thus fast and clean fertilizer is obtained. In this system, it can be benefit from special bacterial culture. When the bacterial culture provide proper temperature and moisture conditions, it becomes possible to achieve rapid compost.
Benefits of compost to soil;
Increases the pore space,
Provides easy processing,
Increases water holding capacity,
Provides better use of nutrients.
Disposal with the method of composting the organic part of municipal waste has great importance. Composting is the highest form of recycling and reuse of resources. In our country, to produce compost from organic fraction of municipal solid waste can be a good solution.
It is one of the most widely applied methods for final disposal of the sewage sludge. Sludge must be stayed on 2,3 seconds at 1200 °C in this process which is applied to remain only fireproof-biodegradable ash after burning of organic matters in the sludge at high temperatures. In incineration processes at the lower temperature, decomposition efficiencies requested in emission value such as dioxin and furan cannot be obtained.
The most important issue in incineration should be avoiding produce gases wastes when disposing of solid and liquid wastes. For this purpose, in incineration plants the important component of investment items is flue gas control and treatment units. In correct design systems, about half of the investment cost is spent for units allocated for emission control.
In our country, cement factories is the primary of the plants which dispose of sewage sludge by burning. Disposal of the sewage sludge is possible also in waste incineration plant.
In some cases, calorific value of sewage sludge turns into alternative fuels from waste sludge. For this, the water content in the sludge becomes important. If the amount of water is more, external fuel is required. It is easier to burn dry sludge. No need for additional heat or fuel to burn sludge, directly affect the attractiveness of the sludge for incineration plant. No need for additional heat or fuel oil sludge affects directly the attraction of the sludge to incineration plants. High calorific value can be purchased commercially. Payment for low calorific value is inevitable.
Drying Processes and ARBIDRY
What is ARBIDRY?
ARBIDRYis the drying combination developed by ARBIOGAZ with the aim of reducing the volume of sewage sludge by drying.
ARBIDRYis an easy solution.
ARBIDRY is an operator friend.
ARBIDRYsystem consists of two major components.
1. Advanced mechanical dewatering with dehydration
2. To reach the ultimate goal of sludge dryness with Solar drying.
In recent years, advanced dewatering technologies that benefit from the magnetic field strength are developed. Arbiogaz is proud of being the company which introduced our country to this technology.
Dehydrators, by using electrical energy as direct current, create (+) and (-) electrically charged regions. In region created by acceptance that solid particles in the sludge cake are (+) charged, free water molecules trapped between cells are removed with a greater efficiency as a result of the compression of particles with magnetic power. Thus, depending on property of the sludge it is possible to reach dryness rate of approximately 40-45%. These rates mean sludge cake volume which consisted after mechanical dewatering decrease by half. This dryness rate is the limit level that can be reached in the dry solid content without applying thermal methods. It is possible to reach more dryness with applying just thermal methods.
Arbiogaz has opportunity to test in field with pilot-scale mobile dehydrator. On this occasion, it is able to determine the maximum solid content of sewage sludge with dehydrator. So far, solid matter content rates between 40% and 60% are found in more than thirty different tests done in treatment plants.
In observations made in terms of energy consumption, when comparing with the energy consumed in thermal drying, saving up to 70% is concerned. With this property, dehydration technology becomes prominent unequivocally in the study of sludge volume reduction.
Please contact our company for detailed information.