Wastewater Treatment Processes PDF

Wastewater Treatment Overview of Waste Water Technologies* used in Food Processing I hope everybody is SAFE and SOUND  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES * Wastewater is the most serious environmental problem in the manufacturing and proce...

Wastewater Treatment Overview of Waste Water Technologies* used in Food Processing I hope everybody is SAFE and SOUND  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES * Wastewater is the most serious environmental problem in the manufacturing and processing of foods. *Most of the volume of wastewater comes from cleaning operations at almost every stage of food processing and transportation operations. * The cost for treating the wastewater depends on specific characteristics of it. Two significant characteristics that dictate the cost for treatment are: the daily volume of discharge and the relative strength of the wastewater the decision is both technical and economical.  Characteristics of wastewaters in agriculture and food processing Wastewater from food processing operations is defined by the food itself. No two plants, even with similar processing capacity of food products, will generate wastewaters of the same quantity and quality because there are too many variables in the process Note: Any quantitative information shown here shall be considered as averaged data. Characteristics of wastewaters in agriculture and food processing Characteristics of wastewaters in agriculture and food processing Characteristics of wastewaters in agriculture and food processing  Parameters for physicochemical treatment of wastewater pH pH is a measurement of the acidity of the wastewater and an indication of growth conditions for the microbial communities used in biological wastewater treatment regimens. pH values vary greatly with the sources of agricultural and food wastewater and with the environmental conditions and duration of storage of the wastewater collected, because these factors dictate the amount of certain substances and decomposition of biological matters as well as emissions of ammonia compounds.  Parameters for physicochemical treatment of wastewater Solids content Solids in wastewaters come in two forms: suspended solids (non-dissolvable) and dissolved solids. Suspended solids are nuisances because they can either settle on the bottom of the receiving water body or float on the surface of the water body. Solids that readily settle are usually measured with an Imhoff cone  Parameters for physicochemical treatment of wastewater Solids content Soluble solids are laboratory measured with evaporation and subsequent weighing of the remaining dry mass of a known amount of water filtrate sample that is collected from the suspended solids measurement or similar pretreatment to remove suspended solids.  Parameters for physicochemical treatment of wastewater Temperature It is generally accepted that the temperature of discharged wastewater to a receiving water body cannot exceed 2–3°C of the ambient temperature in order to maintain population balance of the aquatic ecosystem of the receiving water body.  Parameters for physicochemical treatment of wastewater Odor Odor by itself is not a pollutant, although prolonged and intense exposure has been attributed to adverse effects on wastewater treatment plant workers, and even residents living near the plant, with symptoms such as headache and nausea.  Wastewater Parameters for biological treatment of wastewater BOD and COD The organic matters in food and agricultural wastewater are considerable and complex. Instead of attempting to identify each organic component of The two most common oxygen demand methods of defining organic matters in wastewater are the biochemical oxygen demand and the chemical oxygen demand.  Wastewater Parameters for biological treatment of wastewater COD Chemical oxygen demand (COD) is an estimator of the total organic matter content of wastewaters. COD approach is based on the chemical oxidation of the organic matters in the wastewater: either oxidation of the organic matters by permanganate or oxidation by potassium dichromate (K2Cr2O7). COD analysis using dichromate is the most common method today and is used to continuously monitor biological wastewater treatment systems.  Wastewater Parameters for biological treatment of wastewater COD The COD test utilizes K2Cr2O7 in boiling concentrated sulfuric acid (150°C), in the presence of a silver catalyst (Ag2SO4),  Wastewater Parameters for biological treatment of wastewater BOD Biochemical oxygen demand (BOD) estimates the degree of organic content by measuring the oxygen required for the oxidation of organic matter by the aerobic metabolism of microbial communities. A characteristic simple carbonaceous compound is fructose, and this is oxidized as follows  Wastewater Parameters for biological treatment of wastewater BOD BOD Test: The dilution method is the most common method in use for the wastewater industry and consists of diluting wastewater samples with a nutrient solution (to provide essential minerals for microbial activities), according to wastewater strength, within airtight bottles that are also saturated with air (for facilitating aerobic metabolism), and measuring the dissolved oxygen at the start and periodic intervals of the analysis. A five-day period is generally engaged, and the BOD measured thereafter is called BOD5  Wastewater Parameters for biological treatment of wastewater BOD BOD Test:  Wastewater Parameters for biological treatment of wastewater Total Organic Carbon Total organic carbon (TOC) is a method based on the combustion of organic matters in the wastewater sample to CO2 and water, dehydration of the combustion gases, and running the gases through an infrared analyzer (IR). Nitrogen and phosphorus The sources of nitrogen (N) and phosphorus (P) in food and agricultural wastewater may include artificial fertilizers, synthetic detergents used in cleaning food processing equipment, and metabolic compounds from proteinaceous materials.  BASIC MICROBIOLOGY IN WASTEWATER TREATMENT Important Microorganisms in Wastewater Bacteria and fungi Aerobic bacteria require free dissolved oxygen to decompose organic Materials Anaerobic bacteria live and reproduce in the absence of free oxygen. They utilize compounds such as sulfates and nitrates for energy, and their metabolism is substantially reduced. In order to remove a given amount of organic matters in an anaerobic environment, the organic matters must be exposed to a significantly higher quantity of bacteria and/or engaged for a much longer period of time.  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Physicochemical processes of wastewater treatment are most evident in the primary treatment facilities of a wastewater treatment plant. Physicochemical processes in the primary treatment of food and agricultural wastewater generally comprise a set of unit operations that are intended to remove particulates and other coarse materials from the wastewater stream prior to the secondary treatment processes (mostly biological processes). PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Equalization Basins  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Equalization Basins Flow equalization is not a treatment process or treatment method; it’s a method to improve wastewater treatment processes, whether they are physicochemical processes or biological processes. The purpose of flow equalization is to balance out the process parameters, such as flow rate, organic loading, strength of wastewater streams, pH, and temperature over a 24-hour period.  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Primary Treatment It involves Removal of suspended solids present in Wastewater via filtration or settling: Screening Grit Removal Removal of solids via sedimentation tanks  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Screening Wastewater from food processing or postharvest processing may contain debris, either suspended or floating on the surface. These coarse solids have to be removed at the very beginning of the wastewater treatment  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Coagulation and Flocculation Many substances in wastewater vary greatly in size, from a few angstroms for soluble solids to a few hundred microns of suspended materials. Enmeshment of colloids in wastewater is mainly attributed to precipitation of the insoluble Fe(OH)3 or Al(OH)3 when common coagulants, FeCl3 or AlCl3, are added into wastewater under alkaline conditions. Flocculation is not limited to colloids destabilized by coagulant chemicals and polymers. Aggregation of microorganisms is common in biological wastewater treatment plants.  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Coagulation and Flocculation  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Coagulation and Flocculation Jar test Fill the jar testing apparatus containers with sample wastewater from a stock suspension of known turbidity, color, alkalinity, and pH. Calculate the amount of alkalinity required to react with the maximum dosage of aluminum or ferric sulfate. If necessary, augment the natural alkalinity by the addition of 0.1 N Na2CO3 so that the alkalinity will be at least 0.5 meq/l (25 mg/l as CaCO3).  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Flotation Flotation is a physical process of removing not only oil and grease, but also fine and light suspended particulates from wastewater. Flotation has particular appeal to food wastewater treatment because this source of wastewater contains a substantial amount of oil/grease floating on the surface. The particulates in wastewater that do not settle well and take too much time for settling are also good candidates for flotation treatment.  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Dissolved Air Flotation (DAF) DAF is commonly used in food wastewater treatment. The wastewater feedstock is first pressured with air in a closed tank, and after the wastewater is discharged into a tube in the center of the DAF tank, the air bubbles carry the solids in the wastewater to the surface where they are skimmed by skimmers  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Dissolved air flotation (DAF) Advantages: Reduces oil, grease, and suspended particulates Does not require excessive maintenance or management Disadvantages include the following: Does not remove the BODs associated with soluble materials Disposes and/or treats floats Capital and operating costs could be high  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Sedimentation Sedimentation is the most common physical unit operation in wastewater treatment, more so in primary treatment where sedimentation is the workhorse of the treatment. The term sedimentation is also called settling in some literature. Sedimentation is a process by which the suspended solids, which have higher densities than that of water, are removed from wastewater by the action of gravity in the bottom of the settling tank or basin (also called a clarifier)  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Sedimentation (Clarification)  PHYSICOCHEMICAL WASTEWATER TREATMENT PROCESSES Results of Primary treatment Removal of 25 to 50% of the incoming biochemical oxygen demand (BOD5) Removal of 50 to 70% of the total suspended solids (SS), Removal of 65% of the oil and grease Removal of some organic nitrogen, organic phosphorus, and heavy metals associated with solids are also removed during primary sedimentation.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Biological wastewater treatment is often associated with secondary wastewater treatment and intends to treat the dissolved and colloidal organics after primary treatment. The goal of all biological wastewater treatment systems is to remove or reduce the nonsettling organic solids and the dissolved organic load from the effluents by using microbial communities to degrade the organic load through biochemical reactions.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Aerobic biological treatment dominates secondary wastewater treatment scenes and is performed in the presence of oxygen by aerobic microorganisms (principally bacteria) that metabolize the organic matter in the wastewater, thereby producing more microorganisms and inorganic end products (principally CO2, NH3, and H2O) Aerobic – Aerobic biological processes are common in municipal wastewater treatment. In an aerobic system, the organic contaminants are converted to carbon dioxide, water, additional microorganisms, and other end products  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Anaerobic processes sometimes are also used in the secondary biological treatment of wastewater. Anaerobic processes, in addition to sludge digestion, are employed to treat high- strength wastewater, such as high strength food-processing wastewater streams when the prospect of difficulty associated with oxygen supply to the reactor and large biomass produced in an aerobic process is deemed uneconomical.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Aerobic Lagoons  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Aerobic Lagoons Lagoons are one of the oldest wastewater treatment systems created by mankind. Lagoons are typically large, shallow earthen basins that provide adequate residence time for the wastewater to be treated naturally by both bacteria and algae. A Completely Mixed Aerated Lagoon in wastewater treatment is a relatively shallow basin (with a depth between 1.5 m cm and 5 m) with a large surface area (of several acres) The holding time in a CMAL is typically 7 to 10 days  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Activated Sludge Treatment A suspended-growth aerobic biological process in which microorganisms remove carbonaceous matter from wastewater in an aerobic environment.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Conventional Activated Sludge Process (ASP) This is the most common and oldest biotreatment process used to treat municipal and industrial wastewater. Typically wastewater after primary treatment i.e. suspended impurities removal is treated in an activated sludge process based biological treatment system comprising aeration tank followed by secondary clarifier.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Conventional Activated Sludge Process (ASP)  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Conventional Activated Sludge Process (ASP) The aeration tank is a completely mixed bioreactor where specific concentration of biomass (measured as mixed liquor suspended solids (MLSS) along with sufficient dissolved oxygen (DO) concentration (typically 2 mg/l) to effect biodegradation of soluble organic impurities measured as biochemical oxygen demand (BOD5) or chemical oxygen demand (COD)  BIOLOGICAL WASTEWATER TREATMENT PROCESSES IFAS(Integrated Fixed film Activated Sludge) The IFAS process is typically installed as a retrofit solution for conventional activated sludge systems that are at or beyond capacity.  Enables activated sludge systems to achieve dramatic gains in volumetric productivity without increasing mixed liquor suspended solids (MLSS) levels in the process.  Can achieve stable treatment process under conditions of variable mixed liquor, solids retention, and organic loading rates. Dis: It has high operational cost as it requires a lot of continuous energy.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES IFAS(Integrated fixed film activated sludge)  BIOLOGICAL WASTEWATER TREATMENT PROCESSES IFAS(Integrated fixed film activated sludge) Creation of Anoxic Tank An anoxic zone is created by using an unaerated tank where the dissolved oxygen levels are kept below 1 mg/l  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Rotating Biological Contactor (RBC) An attached-growth process consisting of a series of closely spaced, parallel discs mounted on a rotating shaft which is partially submerged in the wastewater being treated. Microorganisms grow on the surface of the discs where aerobic biological degradation of the wastewater pollutants takes place.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Rotating Biological Contactor (RBC) The RBC process may be used where the wastewater is suitable for biological treatment. The RBC process can be used in many modes to accomplish varied degrees of carbonaceous and/or nitrogenous oxygen demand reductions.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Trickling Filter An attached-growth process where wastewater is distributed over a fixed bed of media such as rocks, gravel, plastic substrate, etc. The wastewater flows downward over the media surface where microorganisms form a layer of biomass and consume contaminants in the water.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Trickling Filter  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Membrane Bioreactor (MBR) Membrane Bioreactor (MBR) is the latest technology for biological degradation of soluble organic impurities. MBR technology has been in extensive usage for treatment of domestic sewage, but for industrial waste treatment applications.  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Membrane Bioreactor (MBR) The MBR process is very similar to the conventional activated sludge process, in that both have mixed liquor solids in suspension in an aeration tank. The difference in the two processes lies in the method of separation of bio-solids. In the MBR process, the bio-solids are separated by means of a polymeric membrane based on microfiltration or ultrafiltration unit, as against the gravity settling process in the secondary clarifier in conventional activated sludge process  BIOLOGICAL WASTEWATER TREATMENT PROCESSES (MBR) vs (ASP)  BIOLOGICAL WASTEWATER TREATMENT PROCESSES Biological treatment processes, in combination with primary sedimentation, typically remove 85% of the BOD5 and soluble solids originally present in the raw wastewater and some of the heavy metals. However, they remove very little phosphorus, nitrogen, nonbiodegradable organics, or dissolved minerals, and in an increasing number of cases this level of treatment has proved to be insufficient to protect the receiving waters from contaminations or to provide reusable water for industrial recycle.  TERTIARY WASTEWATER TREATMENT The treatment processes in advanced wastewater treatment can be simply a number of unit operations added to the existing primary and/or secondary treatment processes (sometimes, this arrangement is called tertiary treatment) Disinfection: Chlorination, ozonation, UV.  Selection of WASTEWATER TREATMENT Technology Selection Criteria Footprint One of the most important that is to be considered during selection of treatment technology is its foot-print area because the value of land is so precious that it is so difficult to get land for states and municipal and if it sis available than it will be so expensive to but that land. So, this factor plays great role and needs to give huge priority for selecting technology.  Selection of WASTEWATER TREATMENT Technology Selection Criteria Operational cost This factors effects the overall cost of running the project for long term.so, we need to concern on this factor too without neglecting its initial cost.  Selection of WASTEWATER TREATMENT Technology Selection Criteria Capability of further Extension Municipal area or growing city has always increasing population and with parallel increase in wastewater production with increase in consumption of food products, increase in facilities and increase in industries and other activities to provide job opportunities to these population. it is certain that all the plant must cope with this condition in future days. So, we must give priority to such technology which give capability to incorporate to this future condition. PLEASE WATCH THE ATTACHED VIDEO