Proposed design of the treatment plant upgrade
The Public Health Regulations of 2010 define the required quality of effluents produced at wastewater treatment facilities in Israel. Association management has expedited the implementation of a general plan for the upgrade of wastewater treatment systems at the plant in order to bring it to the level required by these new more stringent standards. Association management has also decided to provide a response to future population growth in the Association’s member cities. The total quantity of wastewater expected in the year 2030 is approximately 150,000 m³ per day.
The design was prepared by the US firm Hazen & Sawyer in conjunction with the Israeli firm Balasha-Jalon Infrastructure Systems Ltd.
In the framework of the design works, numerous design alternatives for upgrade of the treatment plant were examined, detailed construction and operating cost estimates were prepared for the various alternatives, and a number of pilot installations were commissioned in order to define optimal technologies and dimensions of the various process stages. In addition, detailed tests were performed of all of the existing equipment units at the wastewater treatment plant since a significant part of the process units, other than the pretreatment system, were constructed many years ago and are unsuitable for the modern treatment processes currently being planned.
The upgrade and expansion design for the treatment plant has been approved by the Water Authority, the Ministry of Environmental Protection and the Ministry of Health.
The following is a detailing of the upgrade and expansion design for the treatment plant:
- Pretreatment and preliminary sedimentation
- Secondary biological treatment
- Tertiary treatment including the construction of filtration and disinfection installations
- Sludge treatment
- Treatment Plant Upgrade – Stage I
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Pretreatment and preliminary sedimentation
- The existing pretreatment system is obsolete and no longer meets the needs of the wastewater treatment plant. Consequently, improvements will be made that will include the construction of a completely new system of mechanical bar screens with two filtration grades – the first grade has a filtration opening of 15 mm, while the other has a filtration opening of 6 mm. The function of the mechanical bar screens is to filter and extract organic waste in the raw sewage.
The new pretreatment installations will be designed for an average flow rate of 150,000 m³ per day and will take peak flowrates into account.
- The existing sand removal system is obsolete and no longer meets the needs of the wastewater treatment plant. Consequently, a new installation will be constructed that includes four tanks of the appropriate size in which pumps will be installed for removal of sand and grit in the raw sewage.
- Future expansion to a flow rate of 150,000 m³ per day will be provided through the construction of two additional primary clarifiers.
- Construction of a new air treatment installation to prevent odor nuisances originating primarily from the pretreatment installations.
In order to meet new requirements for effluent quality, the first stage in treatment plant upgrade will begin with the construction of new filtration and disinfection installations that ensure that the required effluent quality is obtained continuously and safely.
(All suspended solids 10 mg/L; BOD 10 mg/L; E. coli 10 units per 100 mL)
The filtration and disinfection system will include granular gravitational filtration tanks on a 1.8 m thick bed with hypochlorite disinfection. The filtration and disinfection units will be constructed for a flow rate of 150,000 m³ per day.
At the conclusion of the works detailed above, the treatment plant will produce effluents at the required improved quality, suitable for unrestricted irrigation in accordance with regulations.
- Treatment Plant Upgrade – Stage II
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Secondary biological treatment
- A new wastewater treatment module will be constructed with a flow rate of 60,000 m³ per day. The module will be built with a biological nutrient removal (BNR) process that enables the removal of nitrogen and phosphorus in accordance with legal requirements.
- Modifications and improvements will be made to the existing aeration tanks of Modules 1 and 3. In this framework, the tanks will be converted into a three stage nutrient removalThe improvements will include the replacement of the aeration system currently based on surface aerators with a system based on bubble aeration and fans with the addition of internal circulating systems compatible with this configuration.
- Following execution of the improvements in Modules 1 and 3, modifications and improvements will be made to Module 2 so that the treatment capacity of the plant will have a capacity of approximately 150,000 m³ per day at the required quality.
- Treatment Plant Upgrade – Stage III
Sludge treatment
The sludge treatment system will be upgraded. The improvements that will be made include the addition of a digester tank and changes in the sludge thickening system in order to enable thickening of the primary sludge (which does not currently undergo thickening) together with the surplus biological sludge. New sludge thickening units will need to be added for this purpose.
- Cost of the treatment plant upgrade and expansion project
Following completion of the treatment plant upgrade project, effluent quality will meet all of the most stringent regulations for wastewater treatment in Israel including forecast changes.
The designer’s estimated cost of this upgrade as detailed above is NIS 485 million.