Sanitary Engineering Lecture 2

Water resource The main resource of water for human uses is rains which occur in the hydrologic cycle, we can take water from rains direct or we can reuse it from the storm water and the wastewater. Water is essentially resource for life; there are many uses for water such as: drinking, agriculture, hygiene, Chemical uses (as a solvent or a solute), heat transfer fluid, extinguishing fires, Recreation, etc….

Hydrologic System Atmospheric system Precipitation Evaporation Evapotranspiration Lithospheric system Stream flow Oceanographic system

Properties of water types Parameter Drinking water Stormwater Wastewater PH 7 5- 8 6-10 Color color ness Muddy brown gray – black Suspended solid mg/L <100 100-400 Total Nitrate mg/L 0-10 12-50 Ammonium N-NH4 mg/L <1.00 15-30

management and solids waste management Types of Collection Systems : Network Design The sanitary engineering became essential with the rapid increase of cities and other rural population concentrations, the sanitary engineering fields include water supply, waste water management, storm water management and solids waste management Types of Collection Systems :   There are two main collecting systems for the wastewater and storm water: Separate system. Combined system.

1- Separate System: A collecting system for wastewater and another separate collecting system for storm water.   Advantages of Separate System: The size of pipes is much smaller than the combined system sewers. This gives the advantage of good hydraulics in the pipe. Smaller pumping stations are needed. Smaller and more efficient treatment plants are needed. Relatively no polluted for the storm water, which mean easy reuse.

Disadvantages of Separate System: The double cost of construction and maintenance. Can't be used at the narrow areas such as the camps. The sediment in the sewers at the dry periods. Combined System : A collecting system that discharge wastewater and storm water through the same conduct. It is preferred for the areas of long rainy seasons. Advantages of Combined System: More economic than separated system in the construction, it's 40% lower in cost than separate system. It is better for areas where it is difficult to construct two pipelines in the street crowded with other services (electricity, telephone, gas, etc….).

Disadvantages of Combined System: Storm water is polluted. Cost of pumping and treatments is increased. The size of the sewer is increased. Overflow occurring is relatively high.

Population estimation Many methods are used to forecast the population in the future. Each method has it’s own assumptions 1. Arithmetic increases method: Assumption: The rate of change is constant (P = population t, = time) Pt = population after time (t). Po= present or initial population Validity: valid only if the curve is close to the real growth of the population in previous years

Example 1: The recent population of a city is 30000 inhabitant. What is the predicted population after 30 years if the population increases 4000 in 5 years. Solution: The arithmetic increase method

2. Uniform percentage of increase: ( Geometric Increase ): Assumption: Uniform rate of increase By integration

Example 2: The recent population of a city is 30000 inhabitant. What is the predicted population after 30 years if the growth rate k= 3.5% . Solution: Uniform percentage of increase (Geometric Increase)

3. Curvilinear method: It is a method of comparison of the city under consideration with similar cities lager in size. 4. Saturation method: In this method, the maximum possible density of population is estimated according to the number of apartments and stories per unit area and the maximum family members. 5. Logistic method 6. Declining Growth method: 7. Ratio method