Wastewater characteristics Nidal Mahmoud Institute of Environmental and Water Studies, Birzeit University nmahmoud@birzeit.edu Ecological Sanitation Training Course SWITCH PROJECT IEWS, Birzeit University, 25-27 January 2011
Outline Introduction General characteristics Wastewater parameters Characteristics of domestic sewage
Introduction Why wastewater characterization Wastewater characteristics for a certain community could change with time depending on technologies available.
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.
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
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).
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)
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.
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.
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.
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
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.
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.
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
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.
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 250 200 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 = 0.986 0 0 25 50 75 100 125 150 NTU Flocculation mixing Primary effluent Sludge discharge Relation between turbidity and particulate t COD (> 0.45 µm) as found in the jar test experiments
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
Particle Size Distribution There is no universal agreement on particle size distribution Type of matter Particle size Suspended matter > 1 µm Colloidal matter 0.001 1 µm Dissolved (or soluble) <0.001 µm Type of matter Particle size Suspended matter > 4.4 µm Colloidal matter 0.45 4.4 µm Dissolved (or soluble) <0.45 µm Importance First step in biodegradation process Treatment method
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, 50-200 mg/l.
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.
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.
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.
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.
Composition of domestic sewage for different countries (Adopted from Mahmoud et al., 2003) Parameter* Jordan Palestine Egypt The Netherlands Columbia, Cali CODt 1183 1586 825 528 267 CODss 608 919 225 CODcol 174 274 156 CODdis 401 393 270 147 112 VFA-COD 104-177 160 55 NH4-N 80 80 26 48 17 Nkj-N 109 104 34 70 24 Total P 13 9 18 1 PO -3 4 -P 13 4 14 Lipids-COD 443 302 Protein-COD 272 224 TSS 420 736 310 215 VSS 330 617 277 108 VSS/TSS 79 84 89 50 Temperature 16-24 8-20 25 * All parameters are in mg/l, except for temperature ( o C), VSS/TSS ratio.
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% 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 time (days)
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) 31-58 Lipids 23 (34) 31 (39) (34.4) ---
Biodegradability of wastewater Biodegradability of the wastewaters Time (day) 130 224 Khirbit As-Samra 56.1 78.4 Abu-Nusier 75.8 (8.6) ---
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 8 1518-3812 2180 663 1411-1844 1586 125 1092-1773 1489 251 Suspended 8 545 1925 1096 456 720-1209 919 157 518-990 725 153 Colloidal 8 107-525 323 101 171-362 274 52.4 213-440 327 71.3 Dissolved 8 468-1482 761 297 280-464 393 62.3 258-613 438 113 Carboh. Total 5 100-231 178.4 52.6 99-166 131 22.8 59-155 93.5 32.7 Suspended 5 45-90 64.1 20.2 67-132 97.4 25.3 28-88 44.8 21.3 Colloidal 5 10-35 21.6 10 9-14 11.7 1.8 4-14 9.9 3.7 Dissolved 5 37-157 92.6 55.4 17-37 22.2 7.4 15-60 38.8 17.3 VFA as COD 2 175-199 187 12 155-162 160 3.1 100-145 123 25.4 Nkj as N 6 54-119 99.4 23.2 85-122 104 14.7 53-83 71 10 NH + 4 as N 8 47-72 58 8.5 72-89 80.1 5 40-77 56.2 9.5 + Proteins 388 224 139 Total PO 4 as P 3 10-15 12.8 2.2 11-14 13 1.5 11-18 15 2.4 PO 3-4 as P 5 6-17 12.4 3.8 8-15 12.9 2.6 8-14 11.9 2.4 SO 2-2- 4 as SO 4 4 474-2060 975 742 129-151 138 9.9 143-277 213 57 TSS 5 510-1096 729 197 610-824 736 67 408-1048 630 234 VSS 5 255-892 584 209 492-676 617 66.1 364-733 480 148 Settleable solids 7 4-105 43.5 41.1 8.5-13.5 10.9 2.2 1.2-8 2.9 2.4 ph 4 7.18-8.02 7.45 0.39 7.16-7.44 7.26 0.13 7.11-7.58 7.31 0.2 T ww Summer 8 26-40 30.9 3.19 24-27 25.8 0.67 20-25 23.4 1.52 Winter 4 12-13 13.13 0.63 T amb. Summer 8 21-33 27.1 3.17 Winter 4 11-17 13.8 2.75 Biodegradability 2 46-49 47 1.4 34-40 36 3.2 32-35 33 1.5 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
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 10 10 9 Acidified of dissolved VFA/CODdis 27 36 35 Hydrolysed dfraction CODdis/CODt 39 28 25 VSS/TSS 80 84 76 CODss/VSS 1.88 1.49 1.51
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 8.8 8.9 6.7 12 PoteinCOD/CODt Protein-COD/CODt 18 14 9 44 VFA/CODt 10 10 9 9 Sub total COD 36.8 32.9 24.7 65
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 590 1270 6.6 1585 935 11.4 1780 1396 255 230 3.8 38 74 4.4 75 35 126 16 60