Wastewater characteristics

Transcription

1 Wastewater characteristics Nidal Mahmoud Institute of Environmental and Water Studies, Birzeit University Ecological Sanitation Training Course SWITCH PROJECT IEWS, Birzeit University, January 2011

2 Outline Introduction General characteristics Wastewater parameters Characteristics of domestic sewage

3 Introduction Why wastewater characterization Wastewater characteristics for a certain community could change with time depending on technologies available.

4 Introduction Water quality is described by a series of water quality parameters A water quality parameter refers to a property of water (such as color, taste, turbidity) or to the composition of water. The composition of water can be expressed in the concentration of individual compounds or it can be expressed in the concentration of a group of related compounds, such as Biochemical Oxygen Demand (BOD), these are called lump parameters. Substances present in water are either in solid, liquid, or gas form.

5 Introduction Water Quality Parameters Physical parameters Chemical parameters Microbiological parameters TS COD coliform VS BOD TSS Nkj-N ph NH4-N N Turbidity NO3 conductivity PO4 SO4 Water analysis is essential in: The design and operation of collection, treatment, and reuse facilities To asses reactor performance To comply with standards others

6 Main components of wastewater characteristics A distinction can also be made according to particle size (important in water treatment as the required treatment process dependsd onthe size of particles to b e removed; also in water treatment).

7 COD fractions Raw sewage 4.4 m paper-filtered sewage Suspended COD (CODss) Colloidal COD (CODcol) 0.45 m membrane filtered sewage Dissolved COD (CODdis)

8 Main components of wastewater characteristics Physical- Chemical Parameters 1. Temperature o C 2. ph Importance Affects chemical reactions and reaction rates. Low temperature affects bacterial growth. Affects chemical biochemical reactions as well as biological activities. 3. Turbidity Due to presence of colloidal matter. When high SS concentration present in WW, it could be resistant to removal when treating under anaerobic conditions.

9 Main components of wastewater characteristics Physical- Chemical Parameters 4. Suspended Solids (SS) 5. Particle size distribution Importance Hydrolysis of suspended solids may be the rate limiting step under anaerobic conditions especially at low temperatures. They also cause disintegration of granular sludge and results in lower methanogenic activity. Affects conversion kinetics of the suspended d solids.

10 Main components of wastewater characteristics Physical- Chemical Parameters 6. Polymeric constituents t (COD) 7. Refractory organics Importance They consist mainly of carbohydrates, proteins and lipids and should be removed with treatment. They constitute the main part of the COD of wastewater. These compounds tend to resist conventional wastewater treatment. Typical examples are surfactants, t phenols and agricultural pesticides. The presence of surfactants also affects stabilization of colloids and the surface properties of particles.

11 Main components of wastewater characteristics Physical- Chemical Parameters 8. Priority pollutants 9. Sulphate Importance Organic and inorganic compounds selected on the basis of their known or suspected carcinogenic, high acute toxicity. Many of these compounds are found in wastewater. High concentration ti causes inhibition of methanogenesis. 10. Chloride It may have an impact on the final use of treated wastewater

12 Main components of wastewater characteristics Physical- Chemical Parameters 11. Heavy metals Importance Toxic to bacteria. Impact on environment. 12. Nutrients Macro (N,P,K) and micronutrients 13. Biological Parameters Important for biological treatment processes. Includes pathogenic microorganisms, and all other organisms participating i in biological conversions.

13 Effect of Temperature Three ranges of temperature Effect of low temperature: low methanogenic activity; low hydrolysis rate. Temperature has also a direct impact on the physical chemical characteristics of the solids and solution, including the ability to form a scum layer. It also affects the solubility of gases.

14 Effect of ph Many inhibitory substances for methanogenic bacteria are controlled by ph. For example, organic acids are inhibitory to methanogenic bacteria only in the unionized i form which h is mainly determined d by the ph of the solution. Optimum m ph for microorganisms growth ph optimum for hydrolysis of organic polymers

15 Turbidity of wastewater Turbidity is an indication of the clarity of a water Turbidity is as an optical property Light source Presence of colloidal particles. Slit Determination of colloidal fraction. Sample Phototube Colloidal particles in anaerobic Schematic diagram of a nephelometer reactor.

16 Turbidity of wastewater Measurement of gas production Turbidity measurements are often used to monitor the performance of treatment works processes: on R line measurement Reactor with filter material From: Mels (2001) ffl t Primary effluent Turbidity measurement Polymer dosing pump Clarifier TSS, mg/l TSSfx T Where, TSS = total suspended solids, mg/l 350 TSSf = factor used to convert 300 turbidity readings to total suspended solids, (mg/l 150 TSS)/NTU 100 T = turbidity, NTU Sludge discharge Particulate COD (> 0.45 µm) 50 Influent Coagulation mixing y = 2.46x R 2 = NTU Flocculation mixing Primary effluent Sludge discharge Relation between turbidity and particulate t COD (> 0.45 µm) as found in the jar test experiments

17 Total Suspended Solids Definition: portion of solids retained on the Whatman glass fiber filter, which has a nominal size of about 1.58 µm Determination: Filtration, drying (105 C), weighing Problems with the test: sensitive to moisture Importance of the test: biological and physical processes

18 Particle Size Distribution There is no universal agreement on particle size distribution Type of matter Particle size Suspended matter > 1 µm Colloidal matter µm Dissolved (or soluble) <0.001 µm Type of matter Particle size Suspended matter > 4.4 µm Colloidal matter µm Dissolved (or soluble) <0.45 µm Importance First step in biodegradation process Treatment method

19 Sulphate concentration Sulphate reducing bacteria are able to oxidize part of the COD present in the wastewater by utilizing sulphate as an electron acceptor. When sulphate concentration is high, then sulphate reducing bacteria will compete methanogenic bacteria and little CH4 is produced. Sulphate reducing bacteria grow at a wide range of ph (5-9). Sulphate reduction can not be controlled in anaerobic reactor except when the SO4- concentration is limited. Fortunately, in domestic sewage, sulphate concentration ti is generally low, for example, mg/l.

20 Polymeric Constituents For domestic sewage, the percentage of each polymer may be different from one community to another depending on the lifestyle and standards of living of a society. Composition affects the biodegradation process as some polymers, for example, carbohydrates are more readily biodegradable than lipids. Organic pollutants in wastewater can be divided into easily Organic pollutants in wastewater can be divided into easily biodegradable materials and slowly biodegradable materials.

21 Biochemical oxygen demand (BOD) Theoretical oxygen demand (ThOD). Organic matter: CnHaObNc CnHaObNc+{n + a/4 b/2 3c/4}O2 nco2 + {a/2 3c/2}H2O + cnh3 BOD: defined as the amount of oxygen required to oxidize organic matter by microorganisms under aerobic conditions.

22 Priority Pollutants The EPA has identified approximately 129 priority pollutants (both organic and inorganic substances), which are suspected to be carcinogenic, mutagenic or have high toxicity. Many of the organic priority pollutants are also classified as volatile organic compounds. These compounds vary depending di on the origin i of wastewater.

23 Refractory organic compounds A typical example on refractory organic compounds is surfactants; or surface active agents. These are large molecules that are slightly soluble in water and cause foaming in wastewater treatment plants. They tend to collect at the air water interface. During aeration of biogas production, these compounds collect at the surface of gas bubbles causing a very stable foam which difficult to remove.

24 Composition of domestic sewage for different countries (Adopted from Mahmoud et al., 2003) Parameter* Jordan Palestine Egypt The Netherlands Columbia, Cali CODt CODss CODcol CODdis VFA-COD NH4-N Nkj-N Total P PO P Lipids-COD Protein-COD TSS VSS VSS/TSS Temperature * All parameters are in mg/l, except for temperature ( o C), VSS/TSS ratio.

25 Biodegradability and Biodegradation rate of sewage Definition of NaOH 10% 5% biodegradability Septum Procedure used for determination Determination of biodegradation rates of different polymers. Serum bottle with ca. 5 g sludge COD + 1 ml NaOH solution = 1 ml of CH4 produced = 2.5 mg COD degraded granular sludge 30 C degr. (1 g VSS) Biodeg graded part 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% time (days)

26 Composition of wastewater (polymeric constituents) Average percentages of carbohydrates, lipids and proteins for the two influents, compared to data presented in literature. Values in brackets are percentages of TSS Khirbit As- Samra Abu-Nusier McInery, Elmitwalli, (1988) (2001) Carbohydrates 5 (21.8) 5 (15) (12.8) 9-17 Proteins 45 (28) 48 (27.1) Lipids 23 (34) 31 (39) (34.4) ---

27 Biodegradability of wastewater Biodegradability of the wastewaters Time (day) Khirbit As-Samra Abu-Nusier 75.8 (8.6) ---

28 Wastewater Characteristics of Ramallah City, Al - Bireh City and Al- Jalazoon refugee camp Parameters # Samples Ramallah Al-Bireh Al-Jalazoon Range AVR STD Range AVR STD Range AVR STD COD Total Suspended Colloidal Dissolved Carboh. Total Suspended Colloidal Dissolved VFA as COD Nkj as N NH + 4 as N Proteins Total PO 4 as P PO 3-4 as P SO as SO TSS VSS Settleable solids ph T ww Summer Winter T amb. Summer Winter Biodegradability Colour 8 Reddish to black Medium brown Light brown All parameters have been measured in duplicate and their units are in mg/l except settleable solid in ml/l; wastewater temperatures (Tww) and ambient temperature (Tamb) (o C); ph no unit; Biodegradability (%); Proteins mg COD/l +Calculated

29 Percentages of hydrolysis and acidification of total COD and acidification of dissolved COD and VSS/TSS and CODss/VSS ratios for the sewage of Ramallah and Al-Bireh cities and AL-Jalazoon refugee camp-palestine Parameter Ramallah Al Bireh AL-Jalazoon Jl Acidified fraction VFA/CODt Acidified of dissolved VFA/CODdis Hydrolysed dfraction CODdis/CODt VSS/TSS CODss/VSS

30 Percentages of carbohydrates, proteins and VFA out of total t COD for domestic/municipal wastewater of Ramallah, Al-Bireh cities and AL- Jalazoon refugee camp-palestine and Bennekom village-the Netherlands Parameter Ramallah Al-Bireh AL-Jalazoon Bennekom-The Netherland Carb-COD/CODt PoteinCOD/CODt Protein-COD/CODt VFA/CODt Sub total COD

31 Gray wastewater characteristics of 25 houses in Biet-Diko and Bilien villages/palestine Item BOD 5 COD ph EC TDS SVI TS TSS Cl - HCO 3 - NH 4 + NO 3 - SO 4 2- PO 4 3- Ca 2+ Mg 2+ Na + K + FC Unit mg/l mg/l μs/ CFU/ cm ppm ml/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l 100 ml value