Fundamentals of Biological Wastewater Treatment

John Wiley & Sons

Chapter One

1.1 Water Supply and Wastewater Management in Antiquity

One of the most ancient systems of wastewater management was constructed in Mohenjo-Daro near the river Indus (Pakistan) at about 1500 BC. Some centuries later, the river moved its course and obviously the town was given up and covered by sand during the following decades. In the 1930s and 1940s, this early high civilization was newly discovered. Private and public houses were equipped with toilets. Water used for washing and bathing as well as rain water flowed through special grooves into canals which were built with the necessary slope to transport the water into the river Indus. These installations demonstrate a high hygienic standard of an early culture.

The main wastewater collector, the Cloaca Maxima, in Rome presumably follows the course of an old ditch which was used at about 500 BC as a collector for wastewater. But soon it was insufficient to handle the flow of wastewater. Therefore, it was enlarged in the following centuries, extended and roofed over (Lamprecht 1988). Archaeological studies presented a nearly complete picture of its line starting from near the Forum Augustum and flowing into the Tiber near the Ponto Palatino. During the time of the emperors (31 BC to 193 AD), the canal could be traveled by boat and could be entered via manholes. The canal has a breadth up to 3.2 m and a height of up to 4.2 m (Fig. 1.1).

In Hellenistic and Roman times, several water supply systems were constructed for Pergamon castle, which is situated on a rock with an 800 m long plateau, at a height of nearly 300 m over the town situated below it. We are here only interested in one of these systems: the Madradag pipe 2 constructed during the rule of Eumenas II (197–159 BC; Garbrecht 1987). This pipe had a length of 42 km and started in the Madradag mountains at a height of 1230 m, that is 900 m higher than the rock of Pergamon. Three valleys had to be crossed and afterwards the Pergamon rock had to be climbed. Therefore, the pipe had to be operated under pressure. This was an extremely demanding requirement for the quality of pipe manufacturing, laying and sealing. The difference in the height of 900 m (from source to castle) corresponding to a pressure drop of 90 bar (9 MPa) alone for the nonflowing water column. Therefore, very stringent requirements had to be met. The pipes were manufactured from fired clay and had a diameter of 16–19 cm. A mean flow rate 15 L s^-1 can be assumed. Initially, only one pipe was needed, but later on, two further pipes of nearly the same diameter were laid in parallel. This made possible an increase in the flow rate to nearly 45 L s^-1 or 162 m³ h^-1.

A system for wastewater management was needed for such a high flow rate of fresh water. The resulting wastewater was collected in carefully masoned collectors laid below a main street covered by rectangular stone plates (Fig. 1.2).

The wastewater flowed from different palaces, temples, public buildings and private houses through clay pipes or open ditches. As a result of the growing flow rate, the cross-section had to be increased from 0.45–0.90 m² to 1.051.70 m² in places (Garbrecht 1987).

To keep the water from draining away at only one place at the end of the collector, discharge pipes took up the wastewater at various points and conducted it to the edge of the rock. From these points it fell below (Fig. 1.3).

1.2 Water Supply and Wastewater Management in the Medieval Age

Monasteries founded by Cistercians, Premonstratensians and Benedictines in Europe during the 12th and 13th centuries were exemplary business undertakings for that time. Besides the monks and the abbot, numerous lay persons worked and prayed there, all requiring a reliable source of water. Frequently, a monastery was placed near a river and a ditch was dug, which was laid with a necessary gradient through the area of the monastery. Figure 1.4 presents a system for water supply and wastewater discharge as a fundamental concept (Bond 1991).

First, the water flowed slowly through two sedimentation basins to a distribution house crossing the main ditch of the monastery. Pipes made either from tree trunks, ceramic material or lead were used for this purpose. From the distribution house, the water flowed to the different consumers, where it was polluted to different degrees; and afterwards it flowed into a wastewater canal, which was divided at two adjustable weirs into two different parts: the smaller one discharging into fish ponds and the larger one flowing below the latrines near the dormitories and afterwards into the river. The not very polluted main ditch was connected with ponds as water reservoirs to drive different mills. For such a demanding water supply, distribution and wastewater discharge, the location of the monastery had to be selected carefully and prepared at great expense.

Figure 1.5 shows an outline of the Cistercian monastery Arnsburg in the Wetterau region of Germany, established there in 1197. There are some differences to the fundamental pattern of water supply, but principally we can recognize several elements that correspond. The mill ditch branching off from the Wetter River first went immediately past a building, presumable the kitchen, and then the water drove a mill (g) and was obviously used for brewing beer (h). Starting from the dormitories of the monks and from the wards, pipes crossed the ditch and flowed into the Wetter River. The brewery was connected by a pipe with the rooms of the abbot and we shall leave unanswered whether the pipe was used for the transport of beer or wastewater. Large parts of the monastery are now completely destroyed, but the location of the cloister, the enclosures and the house of the fountain could be reconstructed after excavations. The mill ditch flowed higher than the Wetter River and supplied the water to drive the mills.

The water supply and wastewater management in the castles of that time were simpler, although in the courtyard a deep well was dug to reach the groundwater. The latrines were constructed so that the waste could fall down upon the sloping rock. For palaces, castles and upper chambers lying next to a river, the wastes could be discharged using an underground canal or an open ditch. Figure 1.6 shows such a canal belonging to a palace from the 12th century in Frankfurt near the river Main, Germany (Grewe 1991).

However, inside the towns there was often no system for waste management up to the middle of the 19th century. Frequently, refuse was discarded directly at the streets and paths where swine and chickens then foraged for usable foods and increased the wastes even further. Only after the installation of a water supply, the use of water toilets and the construction of open (Fig. 1.7) and closed wastewater ditches in the middle of the 19th century did the situation improve.

However, during this period the number of inhabitants in the cities increased considerably. This made it necessary to find a fundamental solution to the problems. In London, for example, they first looked for an interim solution. A large canal was constructed in 1865–1868 along the river Thames (Fig. 1.8), which received most of the countless wastewater streams which were previously disposed directly into the river.

East of London, all the wastes in the canal were again discharged into the Thames. Because of the height difference needed to transport the water, wastewater pumping stations were built at Crossners and Abbey Mills. Fundamentally, this was the same method used in Rome 2000 years earlier: collecting, diverting and discharging.

1.3 First Studies in Microbiology

Antoni van Leeuwenhoek (1632–1723) was the first person able to grind simple lenses and who built the first microscopes (Fig. 1.9). The biconvex lens (L) was fastened between two thin metal plates and the object was mounted up on the pin at (P), which was adjustable by moving two screws. He constructed many of these microscopes and all the necessary lenses he ground himself. The best of them magnified about 200 times (Burdon and Williams 1969). With these instruments, he patiently examined numerous natural objects.

Van Leeuwenhoek grew up in Delft, attended school in Leyden, learned the cloth merchants' trade in Amsterdam and subsequently settled in Delft as a cloth merchant. At the age of 28 (1660), he learned to grind lenses and began to study different small things he found in water droplets. Later on, he started to draw all the things he observed. In 1673, he sent a first letter with some new drawings and descriptions to the Royal Society of London. On 7 September 1674, he reported for the first time about "small animals" (animalcules, protozoa) and small globules (green algae). In his 18th letter, written 9 October 1676, we find the first observations of bacteria, "very small animals", the young of the other animals, as van Leeuwenhoeck assumed (Mockmann and Köhler 1996). In his 39th letter, from 17 September 1683, van Leeuwenhoek enclosed an engraved figure (Fig. 1.10) showing a slide prepared from the film on his own teeth. We recognize cocci, rods and helical bacteria. The Royal Society accepted van Leeuwenhoek as a member in 1680. When he died in 1723, nobody had learned his method for grinding lenses and in the following decades only a few microscopes similar to that of Fig. 1.9 were available.

In 1720, an important book was published in London with the title "A new theory of consumption: more specifically on a Phthisis, or consumption of the lungs", written by Benjamin Marten. In contrast to numerous other hypotheses, the cause of the consumption (tuberculosis) was attributed by Marten to small animalcules (microorganisms), which may come in the lungs by the circulation of blood. They may be contained in the air, can be breathed in and can grow in the blood and the lungs.

However, the scholars of that time believed in a phenomenon which was called abiogenesis. This theory of abiogenesis, or "generatio spontanea" (spontaneous generation of living organisms), is an old hypothesis and was not limited to animalcules. The famous alchemist Johann Babtist von Helmont (1577–1644) thought that animals like the mouse, worms and insects could be created by abiogenesis (Helmont 1652).

This period was concluded in part by experiments, carried out by Franceso Redi (Redi 1667), who worked as a personal physician of Ferdinand II de Medici (the grand duke of Toscana). He distributed a snake, some fish, eels and plates of veal into four bottles and closed them with fine porous gauze. The same remains of these animals were placed into open vessels, in which maggots were living after short time, having developed from eggs which were deposited by flies. In the covered bottles no maggots developed.

The abiogenesis of insects had already been refuted and scholars did not perpetuate this idea, but the discussion of abiogenesis started again in connection with animalcules. In their opinion, they must have been produced by abiogenesis.

In 1711, Louse Joblot studied the development of animalcules in hay and water suspensions (Joblot 1718). First, it was boiled for 15 min and distributed into two vessels. One of them was left open and, after some days, many animalcules had grown. The second vessel was closed with moist, oil-impregnated paper. No life could be observed in this vessel. Only after opening the vessel and waiting for some days did the same effect of growing life present itself, probably observed by using van Leeuwenhoek's microscope. But we can assume that he was not able to observe bacteria.

After these experiments, Joblot was convinced that the observed animalcules were descended from small animals living in the air.

The English priest Father John Turberville Needham (1713–1781) tried to refute this opinion experimentally. He was a resolute advocate of abiogenesis. In order to support this hypothesis, he boiled a suspension of mutton meat, bottled it and sealed the flask from the air with a cork. After some days, the suspension was full of living things. Needham and many other scientists were sure that the theory of preformation was conclusively refuted (Needham 1749, 1750).

Charles Bonnet (1720–1793) was one of the first who questioned whether the flasks were really impenetrable for small animal, or whether there were living creatures or eggs which would be able to survive the heating (Bonnet 1762). The Italian priest Abbate Lazzaro Spallanzani (1729–1799) filled different boiled infusions (1 h) into vessels, which were closed carefully afterwards (Spallanzani 1765). All mixtures remained sterile.

Needham revised this theory: during a heating time of 1 h, a "vegetative power" would be destroyed, which was now introduced into this discussion instead of a biogenesis.

Spallanzani (1776) carried out further experiments in 1776 to test the existence of a "vegetative power". He boiled different infusions, filled them into vessels, closed them and boiled them again for 0.5, 1.0, 1.5 and 2.0 h. Half of them were opened, half of them remained closed. Only in the opened vessels were animalcules observed to be growing. Therefore, a "vegetative power" which could be destroyed after boiling for 1 h could not exist.

Nevertheless, the idea of abiogenesis or generatio spontanea (heterogenesis) as a model for the origin of life from nonliving organics remained a popular theory until 1830. At this point in time, it was shaken more and more by further experiments.

Franz Schulze filled water, meat and vegetables into a glass. At both ends of the glass, vessels were attached which were filled with sulfuric acid (Schulze 1836). From time to time, air was blown into the system (Fig. 1.11a), but all animalcules were restrained and killed off by the strong acid. The organics remained unchanged, no organism was alive. Only after the vessels filled with H2SO4 were removed did the animalcules penetrate from the air into the flask. Schulze proved with this experiment that germs (molecules or particles) distributed in the air of his breath were retained by washing in H₂SO₄, but that they started to digest the organics after entering the open glass.

One year later, Theodor Schwann (1837a) demonstrated that germs could be destroyed by heat. The left bottle in Fig. 1.11b was filled with a heated infusion and connected with a large spherical bottle and a helical tube. Both were heated and the right tube was closed by melting. The organics remained sterile. Obviously, the germs (molecules or particles) could be destroyed by higher temperature.

Schröder and von Dusch (1854) successfully used a layer of cotton as a filter for sterilization (Fig. 1.11c). First, the organic substance in the middle glass was heated and after that a flow of air was adjusted by opening the tap and emptying the left, large bottle slowly. Since then, layers of cotton have been used frequently to sterilize air in microbiology and biotechnology.

Schwann had shown already in 1837 that yeasts are living organisms and that if they grow in aqueous sugar solution and in the absence of oxygen, the sugar is converted to ethanol (Schwann 1837b). This interpretation of fermentation was doubted by scientists over the next 20 years: the conversion of sugar into ethanol must be a purely chemical process!

Nobody was able to describe these germs at this time, but it was known that they grow, that they change organic material and that they multiply. Louis Pasteur (1822–1895) was the first who understood that some germs need oxygen for growing, others do not. If they do not get oxygen, some of them are able to produce lactic acid (Pasteur 1857), ethanol (Pasteur 1860), butyric acid (Pasteur 1861a) and acetic acid (Pasteur 1861b). Pasteur created the foundation of modern biotechnology, which gained considerably in importance during the following decades. In the next years, Pasteur studied the causes of "wine and beer diseases" (Pasteur 1876) as well as poultry pestilence (Pasteur 1880a), anthrax (Pasteur 1880 b) and rabies (Pasteur 1885). All these works laid the foundation for medical bacteriology.

1.4 Wastewater Management by Direct Discharge into Soil and Bodies of Water The First Studies

In the middle of the 19th century, wastewater produced in the fast-growing industrial regions and cities was discharged directly into rivers and canals, as well as into the soil below the toilets at the courtyards of tenement blocks. Frequently, the drinking water pump was located directly next to the toilets. Therefore, it was no wonder that cholera illnesses often occurred, especially in large cities.

Drinking water drawn with these pumps occasionally smelled of H2S; and Rudolf Virchow was the first who assumed that it must be a product of anaerobic reduction of CaSO₄ (gypsum) by "microscopic algae" (Virchow 1868).

The situation in English rivers and canals was characterized by Fig. 1.12, a drawing in the satirical journal "Punch" from 1858 (Fhl and Hamm 1985).

(Continues...)

Excerpted from Fundamentals of Biological Wastewater Treatmentby Udo Wiesmann In Su Choi Eva-Maria Dombrowski Copyright © 2007 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Excerpted by permission of John Wiley & Sons. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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