and the Efficacy of Pit Latrine Additives - Water Research Commission

More documents

Recommendations

Info

APPENDIX D: PROTOCOL FOR TESTING PIT LATRINE ADDITIVES This appendix outlines the methods developed for testing pit latrine additives. Possible mechanisms by which pit latrine additives could affect the mass or volume of the contents of pit latrines are identified. Detailed methodology for undertaking the tests is presented. 1 Pit latrine content samples Pit latrine additive tests were performed on samples that were representative of the material that the additives would be expected to act on, i.e. the top layer of material in a pit latrine. However, previous research has indicated that the composition of pit latrine contents varies considerably and furthermore has been found to contain inhibitory substances added to the pit by the owner; hence additive tests should be replicated on pit latrine material sampled from the top layer (to a depth not exceeding 100 mm) from at least two different pit latrines. 2 Sampling and storage of pit latrine content samples Pit latrine content samples were withdrawn from the pits via the pit backplate using shovels for drier material and buckets for wetter material. Samples were loaded into buckets or jars and sealed to limit exposure to air. (Availability of air assists in biologically mediated oxidation and stabilisation of pit latrine materials; eliminating air as far as possible ensured that the pit latrine samples used in additive trials were not substantially different to the material in the pit.) Sample buckets / bottles were tied into plastic bin bags and transported in closed plastic storage boxes to ensure three levels of containment. Once in the laboratory, samples were thoroughly mixed in an effort to obtain a certain amount of homogeneity between treatments and replicates. Thereafter, a mass of approximately 300 g per jar was added into honey jars, or if trials were not to begin immediately, samples were stored sealed in a cold-room at 4 ºC. 3 Analyses of pit latrine content samples Although the focus of these tests was to determine the efficacy of pit latrine additives for reducing mass and volume it was necessary to obtain a characterisation of the pit latrine material before and after each test to provide back-up information to determine the underlying cause of test observations. Pit latrine content characterisations also provided information that allowed comparison between results from tests using different pit latrine material. Chemical oxygen demand (COD), total solids (TS) and organic solids (OS) analyses were performed in triplicate on whole pit latrine content samples according to Standard Methods (APHA, 1998). A rough measure of pH was obtained using litmus paper. These measurements were used to calculate total sample COD, moisture content, organic solids content and inorganic solids content. All values were calculated on a per g total solids basis to eliminate variations in concentration with time that were due to changes in moisture content. The inorganic solids load of a fixed package of pit latrine material is expected to stay constant over the life of that package of material, i.e. inorganic solids content does not degrade, and should not be transported away from the original package to any great extent. Thus it was reasonable to use 1 g of inorganic solids as a unit for comparison between different samples. However, inorganic solids measurements had a large variance and thus amounts 93
calculated on a per g inorganic solids basis tended to have high uncertainty. Therefore values of COD were reported on a per g dry solids basis. 4 Honey-jar trials The principle of these tests was to quantify mass effects of treatment with pit latrine additives on pit latrine samples without any complicating effects from liquid transport, addition or dehydration. 4.1 Materials and methods The test units consisted of 300 ml plastic jars with screw tops. Approximately 200 g of pit latrine contents was added to each jar and pressed down with a spatula to flatten the surface. The mass of the bottle before and after filling was measured to quantify the mass of pit latrine content. A graduated metal skewer was inserted into the jar in 4 places to measure the height of material in the jar. (After taking this measurement, the surface was smoothed to eliminate the holes made by the skewer). Where necessary, pit latrine additives were made up with water according to manufacturer’s instructions and dosed to the test units on a per area basis according to equation AD-1. dose ml recommended dose 2 ml surfacearea of honey jar m 2 pit latrinem surfaceareof For anaerobic units, lids were screwed tightly to the honey jars, while aerobic units were left open. For each trial, a number of treatments were investigated. equation AD-1 Control: Units containing only pit latrine sample acted as controls so that uncontrolled effects such as natural degradation and dehydration could be quantified. Water treatment: Water was added to these units to quantify the effects of dilution, suspension and water transport on the trials in the absence of other chemical and biological additives Commercial additive treatments: Additives sourced from suppliers and manufacturers were added to test units on a per area basis, i.e. assuming a real pit has a surface area of approximately 1 m 2 (a conservative estimate 1 ) the amount of additive that the recommended supplier’s dosage would provide per unit surface area of the pit was scaled to give the same dose per unit surface area of the experimental “pit”. Three to five replicates were prepared for each treatment. All units were carefully weighed and loaded into storage boxes and placed in fume cupboards. The fume cupboard extractor fans were turned on in order to remove the risk of exposure of laboratory personnel to aerosolisation of pathogens. The storage boxes were closed with lids so that they were not exposed to the draught caused by the extractor fans, but holes were drilled into the sides of the boxes so that air could diffuse in for the aerated units. An open jar containing water was also added to each box to increase the humidity within the box and thereby reduce effect of evaporation on mass and height of contents in each unit. Each unit was weighed on an analytical balance on a daily basis for two or more weeks. At the end of the test period, the units were weighed again and the height of contents was measured in four places with the graduated metal skewer. 1 This means that the additive dosage may have been generous compared to what would be received in a pit latrine, and thus there should have been no negative effect on amount of additive used from downsizing the experiment from full-scale to honey-jar scale. 94
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 and 34:
occur in the absence of oxygen, tak
Page 35 and 36:
(a) (b) Figure 3.2: (a) photograph
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 116: 4.2 Chemical analyses In addition t
show all

and the Efficacy of Pit Latrine Additives - Water Research Commission

Create successful ePaper yourself

Delete template?

Save as template?