and the Efficacy of Pit Latrine Additives - Water Research Commission

More documents

Recommendations

Info

contents. Cell components, particularly cell walls and membranes tend to be difficult to degrade, and may exist intact or semi-intact for a long time. Furthermore, a significant portion of these components are completely non-degradable. Therefore, this general theory suggests that biological processes in layers (iii) and (iv) are dominated by the slow breakdown of poorly degradable cell components, with very little conversion of organic material to methane gas. In degrading intact, but inactive cells, moisture that has been locked into the cell by containment within the cell membrane is released, and may drain away. This results in a slow dehydration of buried pit contents through a combination of biological and physical processes. The theory presented above has been suggested by the results obtained in this and other projects. Many aspects of it have not been scientifically proven, but make logical sense given the broader understanding of the nature of faeces and pit latrine contents, and observations of what is found at different depths within pit latrines. In the sections that follow, the studies that were undertaken within this project are presented and the results interpreted in the light of this theory. 3.2 Observations of pit latrine contents During the planning stages of this project, project aims and methodology were developed based on a fairly naïve perception of what would be found in pit latrines. The purpose of this section is to capture the experiences of the research team relating to what was actually observed in pits to assist in interpretation of experimental results. 3.2.1 Pit latrines in the study areas This study was limited to pit latrines in the eThekwini Municipal area. eThekwini Municipality is the municipal area encompassing the South African city of Durban, and has a sub-tropical climate. Temperatures vary from 10° C to 33° C. It is a summer rainfall area with minimum monthly rainfall below 30 mm in midwinter and above 130 mm in midsummer. There is a very high prevalence of ascariasis in the population within the eThekwini Municipal area. The full history of the latrines visited and sampled within this study could not always be traced because they had been constructed prior to the formation of the municipality. 3.2.1.1 Marian Ridge The pit latrines in Marian Ridge were built at the same time as the houses. They were privately owned. Both the houses and the VIPs were constructed from clay brick. The pits were located within a few metres of the houses. There appeared to be a relatively high employment rate amongst residents; those at home during the working day were usually older women and children. 3.2.1.2 Tongaat The pit latrines studied in Tongaat were constructed by the health department for informal communities living in shacks on the sand dunes. The latrines were communal units, being shared between up to 12 households. Certain of the latrines had been “taken over” by a sub-group within the community and padlocks had been installed on the latrine doors. The pit superstructures were generally in poor repair, and appeared to have been constructed of cement brick. The community appeared to be very poor, with high levels of unemployment. 3.2.2 What is in a pit In many households, a pit latrine serves the dual purpose of providing basic sanitation and storing solid refuse. It has been widely reported in the limited literature on the subject that a large variety of discarded objects and waste are generally found in pit latrines and pose significant difficulties during pit emptying (Mara, 1984; Franceys et al., 1992; Cotton et al., 1995; Still, 2002). Still (2002) reports that 10 to 20% of the pit contents could be made up of non-degradable refuse, although in certain instances, it may be far higher. Every pit latrine that was investigated during the course of this project confirmed this to a greater or lesser extent (Figure 3.2). 13
(a) (b) Figure 3.2: (a) photograph of the inside of a pit latrine located on a steep well-drained slope in Marian Ridge community near Mariannhill, eThekwini Municipality; (b) photograph of contents of pit latrines extracted during a pit emptying exercise in near Tongaat, eThekwini Municipality Pits contained faeces and anal cleansing material as expected. The latter category included toilet paper (occasionally), newspaper, magazines, stones, rags, plastic bags and chip packets. In addition, vegetable waste, plastic and glass bottles and jars, polystyrene, blankets, hats, underwear, toys and a range of other household objects were regularly observed. There was no particular pattern observed in the distribution of different categories of material within a pit. There did appear to be similarities between the contents of different pits within the same community, although these were not scientifically documented. The implication of this observation is that similar user practices exist within a community, but may differ significantly to those in a different community. It is recommended that a systematic record of observations of this type is undertaken in future research into pit latrines. Maggots and worms in pit latrine contents could be regarded as another significant category in pit latrines. Although this project was not specifically concerned with counting and identifying macro-invertebrates in pit latrine contents and therefore did not systematically record presence or relative abundance of these pit inhabitants, nevertheless, it was possible to draw some broad conclusions from field observations. Firstly, the presence of significant quantities of maggots, presumably fly larvae, in pit contents appeared to be related to issues of pit design and latrine maintenance; pit latrines that had missing vent-pipes or back slabs, damaged or inadequate back slabs or pedestals, or pedestals with no lid invariably contained significant maggot populations (Section 4.3.5.3). Pit latrines that were constructed in accordance with general guidelines for VIPs (i.e. with a vent pipe, pedestal lid and properly closed back slab) had significantly smaller observable number of maggots. Many householders have some kind of toilet cleaning routine which may include the use of water and detergents and in some cases disinfectants which ultimately land up in the pit. The frequency and fervour with which the toilet is cleaned may have a significant effect on the contents of the pit; the volume of water added may be significant relative to the total volume of liquid added on a daily basis; disinfectants may have a significant detrimental effect on biological processes that would otherwise occur in the pit since, by their nature, they inhibit or destroy the micro-organisms that carry out these processes. The relative quantities and distribution of different categories of material in a pit will have an effect on the processes that occur in the pit. Some possible mechanisms are: 14
Page 1 and 2: Scientific Support for the Design a
Page 3 and 4: Obtainable from Water Research Comm
Page 6 and 7: EXECUTIVE SUMMARY 1 Introduction Ve
Page 8 and 9: A number of studies in which pit la
Page 10 and 11: in this study were undertaken on pi
Page 12 and 13: from samples were considerable lowe
Page 14: ACKNOWLEDGMENTS This report was com
Page 17 and 18: 3.5 Effect of additional moisture a
Page 19 and 20: LIST OF FIGURES Figure 1.1: Photogr
Page 22 and 23: 1 INTRODUCTION Ventilated improved
Page 24 and 25: pipe and also prevent the exposure
Page 26 and 27: 2 REVIEW OF EXISTING KNOWLEDGE ON T
Page 28 and 29: 2.1.2 Overview of aerobic degradati
Page 30: faeces entering in the prescribed f
Page 33: occur in the absence of oxygen, tak
Page 37 and 38: Aerobic degradation: In the presenc
Page 39 and 40: This section presents data from stu
Page 41 and 42: A practical definition was used to
Page 43 and 44: excess water ingress (e.g. due to h
Page 45 and 46: 3.4.4.1 Summary of results obtained
Page 47 and 48: A homogenous sample was collected f
Page 49 and 50: of this work is that a pit emptier
Page 51 and 52: esults from Study B indicate that b
Page 53 and 54: 300 T3 - faeces + inoculum + Gas pr
Page 55 and 56: the variation observed in the data
Page 57 and 58: conditions. The gas production rate
Page 59 and 60: conditions. Some additives in this
Page 61 and 62: their ability to metabolise mixed o
Page 63 and 64: Table 4.3: Results of field pit add
Page 65 and 66: change in actual volume of pit cont
Page 67 and 68: inwards leaving the pits and their
Page 69 and 70: 4.4 Laboratory-scale testing of pit
Page 71 and 72: Anaerobic units were closed, limiti
Page 73 and 74: The average rate of mass loss in ae
Page 75 and 76: Further, the moisture loss may in f
Page 77 and 78: These results confirm the findings
Page 79 and 80: In a programme of pit latrine empty
Page 81 and 82: The new understanding of processes
Page 83 and 84: 5.4.1.1 Performance of standard VIP
Page 85 and 86:
A further observation was that pede
Page 87 and 88:
5.5.4 Maintenance It was observed t
Page 89 and 90:
This study has not elucidated the m
Page 92 and 93:
REFERENCES APHA, ed. (1998). Standa
Page 94 and 95:
APPENDIX A: PHOTOGRAPHIC DIARY This
Page 96 and 97:
Walls of pit during emptying. This
Page 98 and 99:
Workers engaged in spraying solids
Page 100 and 101:
APPENDIX B: STUDY INTO EFFECT OF MO
Page 102 and 103:
2.2 Gas production from each experi
Page 104 and 105:
NaHCO 3 improved the rate of gas pr
Page 106 and 107:
moisture have a beneficial effect o
Page 108 and 109:
Complete chemical characterisation
Page 110:
Finally, it may also be concluded t
Page 114 and 115:
APPENDIX D: PROTOCOL FOR TESTING PI
Page 116:
4.2 Chemical analyses In addition t
show all

and the Efficacy of Pit Latrine Additives - Water Research Commission

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?