Proses Pengolahan Air Buangan_2 | Sewage Treatment | Nitrogen
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Proses Pengolahan Air Buangan Pengertian, Sumber & Karakteristik Limbah Ida Munfarida, M.Si, MT
What Is Wastewater? Wastewater,” also known as “sewage,” originated from household waste, human and animal wastes, industrial wastewaters, storm runoff, and groundwater infiltration. Air limbah adalah sisa dari suatu hasil usaha dan atau kegiatan yang berwujud cair; (PERATURAN PEMERINTAH REPUBLIK INDONESIA NOMOR 82 TAHUN 2001 TENTANG PENGELOLAAN KUALITAS AIR DAN PENGENDALIAN PENCEMARAN AIR) Wastewater, basically, is the flow of used water from a community. It is 99,94% water by weight (Water Pollution Control Federation, 1980). The remaining 0,06% is material dissolved or suspended in the water.
Sumber limbah Limbah cair domestik adalah cairan hasil buangan yang bersumber dari perumahan, bangunan perdagangan, perkantoran, dan sarana lainnya yang sejenis. Menurut Hammer (1977), volume limbah cair dari daerah perumahan bervariasi, dari 200 sampai dengan 400 liter/orang/hari, tergantung dari tipe rumah. Limbah cair industri adalah cairan hasil buangan yang berasal dari proses/sisa dari suatu kegiatan/usaha industri yang berwujud cair dimana kehadirannya pada suatu saat dan tempat tidak dihendaki lingkungan karena tidak mempunyai nilai ekonomis sehingga cenderung dibuang
Sumber limbah Aktivitas manusia. Jenis aktivitas manusia yang menghasilkan limbah cair diantaranya: Aktivitas bidang rumah tangga, Aktivitas bidang perkantoran, Aktivitas bidang perdagangan, Aktivitas bidang perindustrian, Aktivitas bidang pertanian, Aktivitas bidang pelayanan jasa
Characteristics of Wastewater The nature of wastewater includes physical, chemical, and biological characteristics which depend on the water usage in the community, the industrial and commercial contributions, weather, and infiltration.
Physical properties of wastewater
Physical properties of wastewater When fresh, wastewater is gray in color and has a musty and not unpleasant odor. The color gradually changes with time from gray to black. Foul and unpleasant odor may then develop as a result of septic sewage. The most important physical characteristics of wastewater are its temperature and its solids concentration. Temperature affects chemical reaction and biological activities. Solids, such as total suspended solids (TSS), and volatile suspended solids (VSS), affect the operation and sizing of treatment units.
Solids Solids comprise matter suspended or dissolved in wastewater. Solids are divided into several different fractions and their concentrations provide useful information for characterization of waste-water and control of treatment processes.
- Total solids Total solids (TS) is the sum of total suspended solids and total dissolved solids (TDS). Each of these groups can be further divided into volatile and fixed fractions.
Total suspended solids Total suspended solids (TSS) are referred to as nonfilterable residue. The TSS is a very important quality parameter for wastewater and is a wastewater treatment effluent standard. The TSS standards for primary and secondary effluents are usually set at 30 and 12 mg/L, respectively.
Total dissolved solids Dissolved solids are also called filterable residues. Total dissolved solids in raw wastewater are in the range of 250 to 850 mg/L.
Fixed and volatile solids The residue from TS, TSS, or TDS tests is ignited to constant weight at 550°C. The weight lost on ignition is called volatile solids, whereas the remaining solids represent the fixed total, suspended, or dissolved solids.
Chemical constituents of wastewater
The dissolved and suspended solids in wastewater contain organic and inorganic material. Organic matter may include carbohydrates, fats, oils, grease, surfactants, proteins, pesticides and other agricultural chemicals, volatile organic compounds, and other toxic chemicals (household and industrial). Inorganics may include heavy metals, nutrients (nitrogen and phosphorus), pH, alkalinity, chlorides, sulfur, and other inorganic pollutants. Gases such as carbon dioxide, nitrogen, oxygen, hydrogen sulfide, and methane may be present in a wastewater.
Normal ranges of nitrogen levels in domestic raw wastewater are 25 to 85 mg/L for total nitrogen (the sum of ammonia, nitrate, nitrite, and organic nitrogen); 12 to 50 mg/L ammonia nitrogen; and 8 to 35 mg/L organic nitrogen (WEF 1996a).
The organic nitrogen concentration is determined by a total kjeldahl nitrogen (TKN) analysis Typical total phosphorus concentrations of raw wastewater range from 2 to 20 mg/L, which includes 1 to 5 mg/L of organic phosphorus and 1 to 15 mg/L of inorganic phosphorus (WEF 1996a). Both nitrogen and phosphorus in wastewater serve as essential elements for biological growth and reproduction during wastewater treatment processes and in the natural water.
Biochemical Oxygen Demand The strength (organic content) of a wastewater is usually measured as 5days biochemical oxygen demand (BOD5), chemical oxygen demand, and total organic carbon. The BOD5 test measures the amount of oxygen required to oxidize the organic matter in the sample during 5 days of biological stabilization at 20°C. The ratio of carbon, nitrogen, and phosphorus in wastewater is very important for biological treatment processes. The commonly accepted BOD/N/P weight ratio for biological treatment is 100/5/1; i.e. 100 mg/L BOD to 5 mg/L nitrogen to 1 mg/L phosphorus. The ratios for raw sanitary wastewater and settled (primary) effluent are 100/17/5 and 100/23/7, respectively.
Chemical oxygen demand The chemical oxygen demand is a measurement of the oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidant, such as potassium dichromate. the COD test is useful for controlling and monitoring wastewater treatment processes. The COD test takes 3 to 4 h rather than 5 days for BOD data. The COD results are typically higher than the BOD values. The correlation between COD and BOD varies from plant to plant. The BOD: COD ratio also varies across the plant from influent to process units to effluent. The ratio is typically 0.5:1 for raw wastewater and may drop to as low as 0.1:1 for well-stabilized secondary effluent. The normal COD range for raw wastewater is 200 to 600 mg/L (WEF 1996a).
Biological characteristics of wastewater
The principal groups of microorganisms found in wastewater are bacteria, fungi, protozoa, microscopic plants and animals, and viruses. Most microorganisms (bacteria, protozoa) are responsible and are beneficial for biological treatment processes of wastewater. However, some pathogenic bacteria, fungi, protozoa, and viruses found in wastewater are of public concern.
Indicator bacteria Pathogenic organisms are usually excreted by humans from the gastrointestinal tract and discharge to wastewater. Water-borne diseases include cholera, typhoid, paratyphoid fever, diarrhea, and dysentery. The number of pathogenic organisms in waste-waters is generally low in density and they are difficult to isolate and identify. Therefore, indicator bacteria such as total coliform (TC), fecal coliform (FC), and fecal streptococcus (FS) are used as indicator organisms. total coliform (TC) has long been used as an indicator of pathogen contamination of a water that poses a public health risk.
Fecal coliform (FC), which is more fecal-specific, has been adopted as a standard indicator of contamination in natural waters Fecal streptococci are present in the intestines of warmblooded animals and of insects, and they are present in the environment (water, soil, and vegetation) for long periods of time. Escherichia coli bacteria have also been used as an indicator.
Calculation of bacterial density MPN method. Caliform density is estimated in terms of the most probable number (MPN).
Algae Algae are most commonly used to assess the extent that primary productivity (algal activity) affects the DO resources of surface waters. Many factors affect the distribution, density and species composition of algae in natural waters. These include the physical characteristics of the water, length of storage, temperature, chemical composition, in situ reproduction and elimination, floods, nutrients, human activities, trace elements, and seasonal cycles. the Shannon—Weiner diversity index, is widely used for algal communities or communities of other organisms. The formula is (Shannon and Weaver, 1949):
Contoh Soal A well-mixed 25 mL of raw wastewater is used for TS analyses. A well-mixed 50 mL of raw wastewater is used for suspended solids analyses. Weights (wt.) of evaporating dish with and without the sample either dried, evaporated, or ignited were determined to constant weight according to Standard Methods (APHA et al, 1998). The laboratory results are Tare wt. of evaporating dish = 42.472,3 g
Wt. of dish plus residue after evaporation at 105°C = 42.498,6 g Wt. of dish plus residue after ignition at 550°C = 42.486,3 g Tare wt. of filter plus Gooch crucible = 21.530,8 g Wt. of residue and filter plus crucible after drying at 105°C = 21.544,7 g Wt. of residue and filter plus crucible after ignition at 550°C = 21.534,9 g
Compute the concentrations of total solids, volatile solids, fixed solids, total suspended solids, volatile suspended solids, and fixed suspended solids.