Research Report_CRONULLA wastewater treatment PDF

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Cronulla wastewater treatment(THE LEADER 2014) Research Report – ESE 1: Table of Contents 1 Brief Introduction 1 Identification of Current Design Flow and Future Expected Flow 2 OF WATER/ WASTEWATER TREATMENT EFFICACY 2. Primary Treatment 2.1. Automated screening: 2.1. Grit Removals: 2.1. Sedimentat...

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Research Report – ESE 2021

Cronulla wastewater treatment

(THE LEADER 2014)

Table of Contents 1.INTRODUCTION: ............................................................................................................. 2 1.1 Brief Introduction ................................................................................................................. 2 1.2 Identification of Current Design Flow and Future Expected Flow .......................................... 2

2.DEGREE OF WATER/ WASTEWATER TREATMENT EFFICACY ............................................. 3 2.1. Primary Treatment .............................................................................................................. 3 2.1.1. Automated screening: ........................................................................................................................ 4 2.1.2. Grit Removals: ..................................................................................................................................... 4 2.1.3. Sedimentation: ................................................................................................................................... 4

2.2. Secondary Treatment .......................................................................................................... 4 2.2.1. Bioreactor ........................................................................................................................................... 4 2.2.2. Secondary clarifier .............................................................................................................................. 4

2.3. Tertiary Treatment .............................................................................................................. 4

3.IMPORTANT OF WATER QUALITY PARAMETERS & DISCHARGE STANDARDS AND GUIDELINES: ...................................................................................................................... 5 3.1 Important water quality parameters .................................................................................... 5 3.1.1 Physical Parameters ............................................................................................................................. 5 3.1.2 Chemical Parameters ........................................................................................................................... 6 3.1.3 Biological Parameters .......................................................................................................................... 8 3.1.4. Discharge Standards & Guidelines ...................................................................................................... 8

4. SOME ASPECTS OR UNIT PROCESSES AT THE PLANT ....................................................... 8 5. RECOMMENDATIONS RESPECT TO DESIGN, OPERATION, MAINTAINCE .......................... 9 6.REFERENCES.................................................................................................................. 10

1. 1.INTRODUCTION INTRODUCTION INTRODUCTION:: 1.1 Brief Introduction The latest update of Sydney population is calculated at around 5 million people in June 2019 which is estimated to increase to a range of 5.33-5.84 million by 2025. (Wade, 2020) This growth of population will raise the demand for usable water in Sydney, especially some heavy populated areas. Meanwhile, most of our water usage comes from ground and surface water which is commonly polluted by industrial activity. Therefore, wastewater treatment is an essential process for eliminating pollutions and disposal from our water resource. This allows us to safely access to clean water for daily usage and ensure our ecosystem's health. Sydney Water currently owns 30 water treatment plants including wastewater treatment and water recycling. In which, 16 plaints are wastewater treatment plants which daily treats wastewater for 1.8 million homes and businesses. [1] (Sydney Water n.d.) One of the most prominent plant is Cronulla Wastewater Treatment Plant. The plant has been delivering essential treatment services for its resident and impulse the sustainable growth of our ecosystem and economy in Cronulla-Sutherland area of Sydney since its upgrade in 1999. [4] (Sydney Water n.d.) This report will cover the concept of wastewater treatment, specifically in Cronulla wastewater treatment plant. The report will start with Identification of Current Design Flow and Future Expected Flow of the plant. Three levels of water treatment in the plant will be described including primary, secondary, and tertiary. The insight of water quality parameters and discharge standards that the plant should be adhered to also be described in detail. Furthermore, this report will discuss some of the aspects or unit processes at the plant through an engineering practitioner's perspective. The report will conclude with recommendations with respect to current design, operation and maintenance through resource recovery strategies for future sustainability.

1.2 Identification of Current Design Flow and Futur Future e Expected Flow The Cronulla wastewater treatment plant (CWTP) now has capacity to treat 53 megalitres of wastewater daily to meet the sanitation needs for more than 250,000 residents. The plant is treating wastewater to tertiary standard and then recycle some water on-site for filter backwashes. A part of that treated water is applied for industrial purposes like washing down equipment. The rest of excessive recycled wastewater will be released to ocean at Potter Point, Kurnell. The plant is currently providing far-reaching environmental and financial benefits for the area of 145 km2 around the plant including the suburbs of Cronulla, Sutherland, Helensburgh, Menai, Bundeena and Maianbar. Not only is this profitable for industries in the area, but also be beneficial for the health of the communities and ecosystem. Remarkably, the plant also recycles and produces about 19,000 tonnes of biosolids annually which can be used for composting and fertilisation after treatment. [2] (Sydney Water n.d.)

Sydney Water has recently accomplished the project on odour and corrosion abatement at Cronulla Wastewater Treatment Plant with the expenditure up to $46 million. The purpose of the upgrade is to improve the reliability of the existing infrastructure at the plant and eliminate the risk of odours affecting on the surrounding community. This expansion will create a positive aspect and service for 250,000 properties and visitors to the Cronulla area Moreover, this will also provide a better environment for the aquatic ecosystem to thrive in the near future. [3] (Sydney Water n.d.)

2. 2.DEGREE DEGREE OF WATER/ WASTEWATE WASTEWATER R TREATMENT EFFICACY The treatment in Cronulla Wastewater Treatment Plant includes three levels which are primary, secondary, and tertiary. The detailed levels throughout process will be illustrated by this figure. Figure 1: Flow chart of Cronulla Wastewater Treatment Plant [2]

2.1. Primary Treatment The Primary Treatment is the first level of treatment where large solids are removed from water source by using physical separation processes. The majority of these solids are turned into biosolids and be recycled for beneficial purposes (which will be discussed in the next level). Cronulla Wastewater Treatment Plant have primary treatment with three stages followed order by Step screening, Aerated grit removal and Sedimentation. [2] (Sydney Water n.d.) The Figure 2 below will show the technical data of primary treatment in Cronulla Wastewater Treatment Plant based on different stages with details.

2.1.1. Automated screening: As the water stream is going through this stage, the automated step screen will trap large solids from wastewater and allow the wastewater flow through for the next stage treatment. 2.1.2. Grit Removals: At this stage, air will be injected into a tank which create a vortex. This vortex will fling the grit and isolate them in the bottom. Then a scraper at the bottom will remove them. 2.1.3. Sedimentation: In the next stage the sedimentation tanks are used to sink the solids to the bottom, meanwhile isolate oil and grease float to the top. These solids, oil and grease are separated by scrapers and then be utilised for producing biosolids. At Cronulla plant, a canvas material will be used to cover the top of these tanks, so the odour is managed. The large recycled solids will be transferred to anaerobic digester for handling. These solids will go through two more stage including Centrifuge and Biosolids transport to achieve beneficial reuse.

2.2. Secondary Treatment The Secondary Treatment is the process of nutrient elimination where nutrients such as phosphorous and nitrogen are removed by using physical and biological processes. There will be two equipment utilised in this treatment: Bioreactor and Secondary clarifier. 2.2.1. Bioreactor This first secondary equipment is also known as biological wastewater treatment where a high concentration of micro-organisms (activated sludge) is added to the wastewater. Bioreactor will automatically vary the amount of air that is contained in different parts of the tank. This will ensure that activated sludge will disintegrate nutrients like nitrogen and phosphorous effectively and manageably. 2.2.2. Secondary clarifier The activated sludges then are settled to the bottom of the tank and be removed by scrapers. Some of these activated sludges will be recycle back into the bioreactor. The rest will be continued to produce biosolids. The treated wastewater is then pumped to the clarified tank and ready for the last treatment level. The remaining solids will be distinguished again and be sent to anaerobic digester for handling.

2.3. Tertiary Treatment At this tertiary treatment, the very fine solids such as miniscule solids and floc remained in the treated water from the previous treatment then will be removed by physical processes. The treated wastewater will be then disinfected before it is distributed. The tertiary process at Cronulla plant involves two main stages: filtration and disinfection will be discussed more details below. 2.3.1. Filtration As previously mentioned, the remaining suspended matter are captured by physical processes which is specifically called dual media filtration. This filter applies the downward flow of gravity to trap these very fine solids with various filter media, i.e. coal and sand. (Sydney

Water, n.d.) [5] In water recycling plants such as Rouse Hill Water Recycling Plant, another filtration called shallow bed will be incorporated. This additional filtration utilised flatbed of sand to filter the treated water in combine of physical and biological. So, any other remaining floc and miniscule solids will be filtrated. [6] (Sydney Water n.d.) 2.3.2. Disinfection This is the last stage of Tertiary Treatment for treating water as the treated wastewater is processed through a set of submerged ultraviolet lamps. This ultraviolet light will destroy the micro-organisms by damaging their DNAs. This will ensure the water is disinfected before it is discharged back to the environment or used with other purposes. In compared with other plants, the chemical such as Chlorine is not utilised in this stage of the Cronulla wastewater treatment plant so it will reduce the cost and complexity of the process. The chlorine also possibly leads to toxicity of residuary to aquatic life. It will ensure the final wastewater will not cause impacts on aquatic life after it is discharged to the ocean at Potter Point.

3. 3.IMPORTANT IMPORTANT OF W WATER ATER QUALITY P PARAMETERS ARAMETERS & DISCHARGE STANDARDS AND GUIDELINES: 3.1 Important water quality parameters There are several water quality parameter requirements that must be examined by Sydney Water which consists of physical, chemical, and biological parameters. The wastewater will be examined and evaluated through different parameters via the figure 3 below.

3.1.1 Physical Parameters

The main indicators for wastewater quality in terms of physical determination are Colour, Odour, Solids, Turbidity, and Temperature. Colour contained in impure water is mainly produced from Industrial wastes. The industry activities will lead to various colours in the water which is aesthetically unacceptable and toxic to human and marine life. This will also result in the effectiveness of chlorine as disinfectant in some water treatment plants where there are additional stages of treatment required for purifying and recycling water. Odour occurs from biproducts of biological reactions, minerals, metals, salt, and constituents of wastewater. These not only will cause aesthetical displease. but also, bioproduct of some odours may lead to cancer.

Solids which are insoluble will affect on characteristic operation especially sizing and function of treatment process. The solids potentially agglomerate over time and cause blockage in the equipment. The chart below will show the category of solid sizing in wastewater. (figure 4)

Turbidity is measured by the amount of suspended materials in which light is either absorbed or scattered in the water. The unbalanced level of turbidity will impact on light penetration and disinfection level in the treatment process. This will lead to unpleasing tastes and odours. Temperature with undesirable degree will impact on the oxygen content and biological activity in the water. This implies that water treatment process will be operate differently depended on the weather conditions. Therefore, the reaction rate also varies with different temperature which is calculated by the following formula: 3.1.2 Chemical Parameters Organic Parameters: There are two chemically organic parameters which are generally utilised in determination of water quality: BOD and COD. BOD is abbreviated for Biochemical Oxygen Demand which This directly indicated oxygen requirement of aerobic and heterotrophic bacteria mixture in oxidizing the biodegradable organic carbon matter in a water at specified temperature. It also indirectly signifies the concentration of BOCM in assumption of condition within 5 days at 20 degree, in which only carbonaceous matter is oxidised. COD (Chemical Oxygen Demand) is measured by the number of oxygens required to chemically oxidize all the organic matters in wastewater. Inorganic Parameters Chlorides are widely known with forms such as salts of sodium (NaCl), potassium (KCl), and calcium (CaCl2) in nature. Good amount of Chloride in water will support osmotic activity of body fluids. However, the excessive level of chloride will increase its corrosivity and cause detectable taste in water. (WHO, 2013)

pH is defined as a measure of hydrogen ion concentrated in water which is calculated followed the formula: 𝑝𝐻 = ] The pH value reflects the relative acidity or alkalinity. Pure water has a balanced pH of 7 which is known as neutral. The values lower than 7 indicate acid conditions. Contrary to acid conditions, alkaline conditions indicate pH higher than 7. The figure 7 below will show pH level regarding to specific conditions.

The unbalance of pH in water quality will negatively impact on the health of human and aquatic life. Therefore, it is significantly important to control the pH to its acceptable standards in wastewater treatment procedure. This relates to alum coagulation, biochemical processes and phosphate or iron precipitation. The pH ranges below will provide applicable values in biochemical requirements for aquatic life and miscellaneous microorganism.

Alkalinity is defined as a measurement of HCO3 –, CO3 2– and OH– concertation in the water. This Alkalinity value can be achieved by titrating with HCl to certain end-point pH values. Water with high pH like alkaline can lead to strong distastes. The acidic and alkaline imbalance from discharged water may be hazardous to infrastructure waterways and aquatic life. Nitrogen and Phosphorus are chemicals that provides essential nutrients for the growth of plant and aquatic animal. However, the overabundance of these chemicals will result in algal blooms and excessive aquatic plant growth in waterways (Eutrophication). The removal of Nitrogen is operated by aerobic and anoxic processes. Meanwhile Phosphorus is removed by phosphate accumulating organisms (POAs). [7] (Sydney Water n.d.) Sulfur is known as a condition occurred when water is exposed to hydrogen sulfide gas. The sulfur will lead to unpleasant smell and taste. Therefore, it will be trapped by carbon filters and some unique media in water treatment process. [7] (Sydney Water n.d.)

Gases Methane (CH4), Oxygen (O2) and Hydrogen Sulfide (H2S) are also considered in water testing quality process. These gas leaks in construction tunnels, mines and chemical plants which will cause significant effects to human and aquatic life. 3.1.3 Biological Parameters The removal of pathogenic bacteria, viruses and other biological organisms is one of

the most critical process in water treatment. The pathogen’s presence in the water will lead to different kinds of health issues in human and aquatic life. Therefore, this is significantly important to monitor and control the parameter of these biological pathogens. Especially virus such as COVID-19 and variables at the moment are highly contagious and should be closely control. 3.1.4. Discharge Standards & Guidelines Through the significance and seriousness of discharge wastewater to environment described above, reasonably, the threshold limits to the discharge of wastewater are established to ensure safety for workers within plants and the wastewater system. These will ensure that the discharge wastewater is monitored and managed, therefore, the health of us and our ecology will be ensured and thrive. The figure 10 below shows Discharge Standards for Industrial Wastewater Treatment. (Khan, 2021)

The direct discharge to waterways requires complete treatment. Meanwhile, for the wastewater in sewer, it will be dependent on the capacity of the sewers and treatment plants. However, discharged water in any cases must satisfy the operating regulations established by relevant governing bodies. Discharged water standards from Industries in Sydney NSW is exclusively established and managed by Sydney Water and NSW Environmental Protection Authority (EPA). [1] (Sydney Water n.d.)

4. SOM SOME E ASPECTS OR UNIT PROCESSES AT THE PLANT As a new engineering practitioner, I surprisingly discovered how the wastewater is carefully treated in the Cronulla wastewater plant through different levels of treatment. Wastewater treatment process is not simply understood as Degree of wastewater treatment in theory.

There are a lot of aspects and elements that are contained within must be considered. The findings related to chemical parameter has expanded my knowledge of wastewater treatment process. The water not only be evaluated by exterior aspects such as colour or odour. But also requires various evaluation parameters to examine its quality. I was amazed by how the activated sludge is utilised for secondary treatment as well as its ability to recycle. Before the research, I expected that chlorine was supposed to be used in any of water treatment plant. But I found out how Chloride is not involved in the Cronulla plant's treatment process due to complexity and cost-efficiency. The individual usage of ultraviolet light in the disinfectant process still show efficiency in treatment for its communities.

5. RECOMME RECOMMENDATIONS NDATIONS RESPECT TO DESIGN, OPERATION, MAINTAINCE 5.1. Design The capacity of treatment areas is widely served but in terms of demands and needs for the growth of the current population in areas, it must be continuedly improved and expanded. Therefore, it is essential for considering the construction of additional facilities and equipment as well as its sizing in order to provide better service in the future. The consideration must include both economic and environmental aspects. Not only design in production is needed to...