Early Biological Wastewater Treatment Processes

The collection of wastewater in canal systems served a purpose, but its discharge into rivers was no solution of the problem, if the amount of wastewater discharged was too great in comparison with the river flow rate. In Berlin, Hobrecht proposed and built a wastewater collecting system consisting of 12 radial arms - five to the south and seven to the north of the river Spree. In each radial system, rainwater and wastewater flowed to a central lowest point by gravity (and the system is still in use today), from where it was pumped in pipes to an irrigation field outside the city. In the middle of each irrigation field, the water exited through a standpipe and gate valves through irrigation ditches in the irrigation fields. The water seeped through the ground and was collected by porous ceramic pipes and flowed into drainage channels and finally into canals or rivers (Hobrecht 1884). Similar irrigation fields were built in the surroundings of several other cities. Data for concentrations measured in the influent and effluent are very rare. Table 1.1 shows some data from 14 April 1891 for the irrigation field in Breslau (Uffelmann 1893). If we compare the values for dissolved organics of 155.9 mg L-1 (influent) and 53.2 mg L-1 (effluent), we can conclude that about 66% was removed. Nitrification was nearly complete (ammonia 105^7 mg L-1).

The cleaning effect of irrigation fields had already been proven in the late 1870s, but in the first decade of operation, the scientific basis for the reduction of organics, which was being monitored by smell (often) and/or by taste (seldom), was largely unclear. During the 1890s, it became more and more certain: it was not a chemical but a biological process performed by aerobic and anaerobic bacteria. Nevertheless, the dispute was not resolved until the beginning of the 20th century (Dunbar 1912).

Table 1.1 Concentration of samples from the influent and effluent of an irrigation field in Breslau (14 April 1891; Uffelmann 1893, extract).

Substance

Concentration (mg L

-1)

Influent'1

Effluentb1

Suspended material

295.2

54.0

Organics

246.0

-

Inorganics

49.2

-

Dissolved material

687.3

478.4

Organics

155.9

53.2

Inorganics

531.4

425.2

KMnO4 consumption

118.1

9.7

Ammonia (NH3 + NH+)

105.0

7.0

Nitric acid

-

17.5

Phosphoric acid

22.4

-

a) Pump station. b) Mean dewatering ditch.

a) Pump station. b) Mean dewatering ditch.

1.6 Early Biological Wastewater Treatment Processes 15

Experiments in ways to increase the specific wastewater load (in m3 (ha day)-1) compared with that of irrigation fields resulted in the development of intermittent soil filtration. The following operational conditions had to be met for the first sites: (a) the groundwater level must be low enough, (b) the percolating water must be collected in lateral ditches for recycling and (c) the application of wastewater must be intermittent, so that water levels in the ground recede and allow the simultaneous flow of air downwards to provide oxygen for bacterial growth, respiration and degradation of organics. Although this biological process was not completely understood, it was tested with increasing success.

One of the first of this kind was operated successfully in Lawrence, Massachusetts, USA, in 1888. These first experiments were very successful, showing nearly complete removal of organics and complete NH4+ oxidation (Dunbar 1899). In London and its surroundings, similar experiments with intermittent soil filtration were carried out by Dibdin in 1894-1896 (Roeckling 1899). In Barking Creek, London, near the river Thames, an area of 4047 m2 was built up with soil that had walls 1 m high, supported by laid bricks. Several solid materials were tested as a contact bed. This filter was periodically filled with wastewater over 2 h, stopped for 1 h and emptied slowly over 5 h; and the cycle was repeated every 8 h. About 70-75% of the dissolved organics were removed. The plants in Sutton and Exeter were different from that of Barking only in one point: the wastewater was biologically pretreated for 24 h - in Sutton apparently aerobically in an open vessel and in Exeter anaerobically in a closed vessel. In both plants, the results were somewhat better than in Barking (Dibdin 1898). Similarly, very early pilot plants for the study of biodegradation went into operation in 1897 in Hamburg (Eppendorfer hospital; Dunbar 1899), in Großlichterfelde near Berlin, in 1898/1899 (Schweder 1901) and in Tempelhof near Berlin in 1900 (Thumm and Pritzkow 1902). After the foundation of the "Königliche Prüfanstalt für Wasserversorgung und Abwasserbeseitigung" in Berlin, pilot experiments were carried out systematically to study intermittent soil filtration, in order to find the best type of contact beds and to improve the process in Tempelhof (Thumm and Pritzkow 1902; Zahn 1902). All these experiments and developments led finally to the development of continuously operated trickling filters (Table 1.2). One of the first large-scale plants was built in the form of contact beds using large pieces of coke and operated with intermittent filtration, in Stahnsdorf near Berlin (Müller 1907).

Table 1.2 Development of irrigation fields and trickling filters - increase in specific load. Year Process Specific load

1886-1900

1860 1878 1884

1890 1903 1960

Irrigation fields prepared on suitable soil and level area

Irrigation fields with drain trenches and soil fields

Irrigation fields and preliminary sedimentation

Intermittant soil filtration

Intermittant filtration with contact beds

Trickling filter

High-load trickling filter

500-2000 8000

16 | 1 Historical Development of Wastewater Collection and Treatment 1.7

Going Green For More Cash

Going Green For More Cash

Stop Wasting Resources And Money And Finnally Learn Easy Ideas For Recycling Even If You’ve Tried Everything Before! I Easily Found Easy Solutions For  Recycling Instead Of Buying New And Started Enjoying Savings As Well As Helping The Earth And I'll Show You How YOU Can, Too! Are you sick to death of living with the fact that you feel like you are wasting resources and money?

Get My Free Ebook


Post a comment