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Microbiology Research 2018; volume 9:7269

Use of slow sand tries.2,3 According to the World Health technique to improve Organization (WHO), 10% of the world’s Correspondence: Chebor Joel, Department of population relies on food grown with con- Biological Sciences, University of Eldoret, taminated wastewater.4 P.O. Box 1125, Eldoret, Kenya. for crop Wastewater has many advantages E-mail: [email protected] including supplying both organic matter and mineral nutrients to soil that are benefi- Key words: Slow sand filtration, effluent, irri- Chebor Joel, Lizzy A. Mwamburi, gation, wastewater, seasons. Ezekiel K. Kiprop cial to crop production, and reduce the cost of fertilizer for crop application.5 Department of Biological Sciences, Contributions: CJ, conception and design of Conventional the research article; LAM, analyzing and University of Eldoret, Kenya methods that are aimed at reducing the pol- interpreting the data; EKK, revising critically lutant load on the environment in most the article for important intellectual content. cases release that are still high in All the authors approved the study. Abstract Biological Demand (BOD), nitro- gen and phosphorous nutrients and bacterial Conflict of interest: the authors declare no scarcity has resulted to urban resi- load thus posing danger to the receiving potential conflict of interest. dence to resort to using untreated wastewater environment.6,7 Health problems and dis- to irrigate their crops. This practice raises Funding: none. concerns on health of the farmers and con- eases are often caused by discharging sumers of the crops. The study aimed at untreated or inadequately treated effluent Acknowledgements: the authors sincerely determining whether the effluent from into the soil for agriculture. Slow sand fil- appreciated Eldoret Water and Sanitation Boundary Treatment Plant was up to tration is a simple technology that can be Company (ELDOWAS) for according the per- used to reduce the load of wastew- mission to undertake this research at their national and international standards recom- 8,9 mended for irrigation, if not they were fur- ater to the standards for irrigation. facility and also for the assistance with their equipments, consumables and technical staff ther subjected to slow sand filtration of dif- However, little work has been done on the which made us to achieve the objectives of ferent sand sizes (0.1 and 0.05 mm) to polish application of Slow Sand Filters (SSFs) in only 10 this study. the effluent. Pour plate method was used to wastewater quality improvement. The process is passive and the effectiveness of determine total coliforms (TC), Biological Received for publication: 31 July 2017. the filters is dependent upon the develop- oxygen demand (BOD) technique for BOD, Revision received: 26 September 2017. ment of a biofilm attached to sand grains.11 chemical oxygen demand (COD) digestion useAccepted for publication: 1 December 2017. for COD, gravimetric method for total dis- With increased volumes of untreated or solved solids (TDS) and total suspended partially treated wastewater being used for This work is licensed under a Creative solids (TSS). One sample t-test during dry crop irrigation, there is need to develop reli- Commons Attribution NonCommercial 4.0 season showed that BOD, COD, TC and TSS able methods to mitigate the health risks License (CC BY-NC 4.0). in the effluent were significantly higher that can be caused by microorganisms in water and other physicochemical sub- ©Copyright J. Chebor et al., 2018 (P<0.05) than the standards for irrigation. Licensee PAGEPress, Italy During wet season BOD, COD, TDS and pH stances. The objectives of this study were to Microbiology Research 2018; 9:7269 were significantly not higher (P>0.05) than quantify the amount of the microbiological doi:10.4081/mr.2018.7269 the compared standards for the wastewater to and physiochemical parameters in the efflu- be used for crop irrigation. The filters ent obtained from Boundary Sewage improved the effluent from the treatment Treatment Plant and compare it with nation- al and international standards for treated primary ponds, 1 secondary pond, 1 sedi- plant to the standards for irrigation. The mentation pond, 1 tertiary pond and 2 trick- sequential treatment of the raw wastewater wastewater to be used for crop irrigation. If the effluent was not up to the standards then ling filters. The study was carried out dur- by the Boundary Plant ing dry and wet seasons where parameters and the slow sand filtration technique made the effluent was subjected to slow sand fil- tration for further purification. were tested in three replicates. Sewage the wastewater to achieve the standardsNon-commercial it can treatment at Boundary Treatment Plant be utilized for crop irrigation. takes 13 days from the inlet to outlet. It takes four days at the primary pond, approx- Materials and Methods imately two minutes at the filter, few min- Introduction Study area utes at the sedimentation tank, four days at In many countries water is becoming an The study was carried out at Boundary secondary pond, and five days at the tertiary increasingly scarce resource. Due to Sewage Treatment Plant in Eldoret, Uasin pond. In the present study, samples for anal- increasing population and industries as well Gishu County, Kenya. The plant is located ysis were collected as follows: inlet sample as urban expansion, the production of at latitude of 0.520 N and 35.280 E. It is one on day one, primary pond sample after four wastewater and its reuse has grown rapidly. of the conventional wastewater treatment days, filter sample same day as primary The reuse of treated wastewater for irriga- plants within Eldoret town, it treats both pond sample and final effluent after nine tion is a practical to overcome industrial and domestic wastewater. days. Five litres of the final effluent was water scarcity, especially in arid and semi- Furthermore the plant also receives domes- taken to the laboratory and passed through arid regions.1 Wastewater has long been tic wastewater from the latrines and septic the three sand filters. The collected samples used as a resource in agricultural produc- tanks from various households within the from the treatment plant were analyzed for tion. It has recently been approximated that town which are transported by honey sucker BOD, chemical oxygen demand (COD), about 20 million hectares of land are irrigat- truck to this treatment plant for disposal. total coliforms (TC), pH, total dissolved ed with treated, partially treated, diluted and The plant relies almost entirely on micro- solids (TDS) and untreated wastewater in developing coun- bial treatment of waste; it has 1 screen, 2 (TSS) and then compared with both nation-

[page 14] [Microbiology Research 2018; 9:7269] Article al and international standards for treated × 1000 ÷ Sample volume wastewater to be utilized for crop irrigation. Chemical oxygen demand Where A = weight of dried residue plus After comparing, the quantity of these COD was determined as described in dish in mg and B = weight of dish in mg parameters in which the treatment plant COD manual (2002) where 100 mL of the failed to treat to the standards for irrigation, final effluent and filtrate samples were first pH one and half litres of the final effluent were homogenized in a blender. Two millilitres The pH of the final effluent and filtrate passed through each of the assembled slow of the homogenised samples were pipetted was obtained by using pH meter. sand filters of grain sizes, 0.1 mm, 0.05 mm into low range reagents. Two millilitres of and a combination of the two sand sizes on deionised water was added to the reagents Statistical analysis a 26 feet plastic PVC pipe. The filtrate to produce a blank, then the vials were The data obtained from the final efflu- obtained from this filters were collected and inverted gently several times and placed in ent and the filtrate during the two seasons further analyzed and compared with the a COD reactor which had already been were analysed by one sample t –test proce- same standards for irrigation. heated to a of 1500C and left to dure using SAS 9.2 software in comparison Biological oxygen demand and TSS heat for two hours. After this duration the with the various standards for sufficiently were compared with United States of vials were removed to cool to room temper- treated wastewater to be used in irrigation. America (Washington) standards, COD ature and finally a programmed Significance level of 95% was used. with standards of Jordan, while TC, pH and Spectrophotometer machine was used to TDS were compared with the Kenyan read the COD results. national environmental management Results authority (NEMA) standards for treated Total suspended solids wastewater to be used for irrigation. The The TSS was obtained by the procedure Comparison of the final effluent standards for irrigation for the various described by Eaton.14 A glass filter was with recommended standards for parameters were obtained from various dif- dried by placing it in an oven with a temper- irrigation during dry season ferent countries that uses treated wastewater ature of 1030 C for 60 minutes, removed and The quantity of Biological oxygen for irrigation because Kenya NEMA did not then put in a dessicator to cool for 60 min- demand,only chemical oxygen demand, total provide all the standards for all the parame- utes and weighed. A 100 mL of the suspended solids, and ters for the treated wastewater to be used for homogenised sample was filtered through pH in the final effluent from Boundary irrigation because irrigation in Kenya with the glass filter. The weight of the sample Sewage Treatment Plant were compared wastewater whether treated or not is not was obtained by using the formula:use with the standards for treated wastewater to allowed by the law however, poor urban Total Suspended Solids (mg)/L = (A–B) be used in crop irrigation during dry season residence practice it illegally. × 1000 ÷ Sample volume as demonstrated in Table 1. Where A = weight of filter plus dried The quantity of pH and TDS in the final Total coliform analysis residue in mg and B = weight of filter in effluent from Boundary Wastewater Final effluent and filtrate samples col- mg. Treatment Plant were not significantly lected were serially diluted then pour plate (P>0.05) higher than the recommended technique as described by Ramesh12 on Total dissolved solids standards of between 6.5 and 8.5 for pH and Eosin Methylene Blue was used and incu- The filtrate obtained from the testing for of ≤1200 for TDS for the treated wastewater o bated at 37 C for 24 hours. Nucleated Total Suspended Solids described above to be used in irrigation during dry season. colonies with or without metallic sheen and was utilized for testing for Total Dissolved However, the quantity of BOD, COD, TC pink in colour were counted with the aid of Solids by transferring them to a weighed and TSS in the final effluent were signifi- Gallenhamp colony counter. The popula- evaporating dish and then evaporated to cantly (P<0.05) above the standards recom- tions of the viable colonies were obtained dryness on a steam bath. This was followed mended for the wastewater to be used for by the formula; number of counted colonies by drying for one hour at 1800 C then cool- irrigation of ≤30 mg/L, ≤100mg/L, 13 × dilution reciprocal. ing for one hour in a dessicator.14 ≤1000mg/L, ≤ 30 mg/L for BOD, COD, TC Weight of TDS was obtained using the and TSS respectively during dry season Physicochemical analyses Non-commercialformulae by Eaton.14 hence rendering the treated wastewater Biological oxygen demand Total Dissolved Solids (mg)/L = (A–B) unsuitable for irrigation during dry season. BOD was determined by the procedure described in BOD track manual (1995- 1998). inhibitor powder was dispensed into the empty sterile BOD bot- Table 1. Comparison of final effluent with the recommended standards for treated waste- tle. Collected samples of 0.32-1.1 litres water to be used for irrigation during dry season. were homogenised in a blender for two Parameters Mean±SE Recommended standards P-value minutes. The pH of the sample was adjusted to a range of 6.5 and 7.5 with Sulphuric BOD (mg/L) 82.67±4.33 ≤30 (mg/L) (Washington) 0.0034 or Sodium hydroxide then 355 mL of the COD (mg/L) 169.0±0 ≤100 (mg/L) (Jordan) <.0001 sample was measured into the BOD. A 3.8 pH 8.05±0.03 ≥6.5 (NEMA) 0.9998 cm magnetic stir bar was placed in each sample bottle then stopcock grease was pH 8.05±0.03 ≤8.5(NEMA) 0.9982 applied to the seal lip of each bottle and to TC (cfu/100mL) 4500.0±0 ≤1000 (cfu/100 mL) (NEMA) <.0001 the cap of each seal cap. One gram Lithium TDS (mg/L) 722.7±9.21 ≤1200 (mg/L) (NEMA) 0.9998 hydroxide powder pillow was added to each TSS (mg/L) 90.00±0 ≤30 (mg/L) (Washington) <.0001 seal cap. The bottles were incubated for five BOD, Biological Oxygen Demand; TDS, Total Dissolved Solids; COD, Chemical Oxygen Demand; TSS, Total Suspended Solids; TC, Total col- days in a BOD incubator. iforms; NEMA, Kenya National Environmental Management authority.

[Microbiology Research 2018; 9:7269] [page 15] Article

Comparison of the final effluent of treated wastewater to be utilised in irriga- mended for irrigation during wet with the recommended standards tion. BOD of 27.67 mg/L was lower than 30 season for irrigation during wet season mg/L, COD of 62.33 mg/L was lower than Total coliforms and TSS that were not The parameters that were determined at recommended standards of less than 100 treated by Boundary Sewage Treatment the final effluent at the Boundary Sewage mg/L, TSS of 23.33 mg /L was lower than Plant during wet season to the recommend- Treatment Plant were compared with the compared standard of 30 mg/L and TC of ed standards for irrigation (Table 2) were 600 cfu/100 mL was lower than the com- standards for wastewater to be used in irri- subjected to slow sand filtration for further pared standard of 100 cfu/100 mL. gation during wet season as shown in Table treatment in an effort to improver them to All the parameters; BOD, COD, TSS 2. pH, BOD, COD and TDS in the final be suitable for irrigation. Three types of and TC tested in the filtrate from slow sand effluent from Boundary Sewage Treatment slow sand filters made were employed, one filter made of mixture of 0.1 mm and 0.05 Plant during wet season were significantly was made of 0.1 mm sand size another was mm sand sizes were significantly not not (P>0.05) higher than the standards rec- made of 0.05 mm and another was com- (<0.05) higher than the compared standards ommended for irrigation. pH in the final posed of mixture of 0.1 mm and 0.05 mm for treated wastewater to be used in irriga- effluent during wet season was within the sand sizes. The findings were s shown in tion. Biological oxygen demand of 28.33 range of between 6.5 to 8.5 for treated Table 4. mg/L was lower than the recommended wastewater to be used for irrigation, Total coliforms in the filtrate from 0.05 standard for irrigation of 30 mg/L, COD in Biological Oxygen Demand, chemical oxy- mm slow sand filter during wet season were the filtrate of 70.00 mg/L was below the gen demand and total dissolved solids were significantly not (>0.05) higher than the irrigation standard of ≤100 mg/L, TSS of compared standards for the filtrate to be below the recommended standards for 26.33 in the filtrate was within the standard wastewater to be used for irrigation of ≤30 used for irrigation. The706.7 cfu/100 mL of for the filtrate to be used in irrigation of ≤30 total coliforms in the filtrate were less than (mg/L), ≤100 (mg/L) and ≤1200 (mg/L) mg/L and TC of 813.3. cfu/100 mL was respectively. However, TSS and TC were the compared amount of ≤1000 cfu/100 mL. within the standard of ≤100 cfu/100 mL for The amount of total suspended solids in the significantly (P<0.05) higher than the rec- the filtrate to be used in irrigation. filtrate were significantly (<0.05) higher ommended standards for irrigation render- Comparison of the filtrate with the than the compared standard for the filtrate ing the wastewater unsuitable for irrigation. only recommended standards recom- to be used for irrigation. Total suspended solids and total coliforms were above the standards for irrigation of ≤30 (mg/L) and ≤1000 (cfu/100 mL) respectively (Table 2). use Table 2. Comparison of the final effluent with the standards for treated wastewater to be Comparison of the filtrate with the used in irrigation during wet season. standards recommended for irriga- Parameters Mean±SE Recommended standards P-value tion during dry season Biological oxygen demand, chemical BOD (mg/L) 28.00±0 ≤30 (mg/L) (Washington) 1.0000 oxygen demand, total suspended solids and COD (mg/L) 76.67±0.33 ≤100 (mg/L) (Jordan) 0.9999 total coliforms that were not treated by TC (cfu/100 mL) 1600.0±0 ≤1000 (cfu/100 mL)(NEMA) <.0001 boundary wastewater treatment plant during TDS (mg/L) 357.3±3.67 ≤1200 (mg/L) (NEMA) 1.0000 dry season to the recommended standards for the treated wastewater to be used in irri- TSS (mg/L) 62.00±1.00 ≤30 (mg/L) (NEMA) 0.0005 gation (Table 3) were subjected to slow pH 8.03±0.03 ≥6.5 (NEMA) 0.9998 sand filtration of three sand filters; 0.1 mm, pH 8.03±0.03 ≤8.5 (NEMA) 0.9975 0.05mm and the mixture of the two (0.1 mm BOD, Biological Oxygen Demand; TDS, Total Dissolved Solids; COD, Chemical Oxygen Demand; TSS, Total Suspended Solids; TC, Total col- and 0.05 mm) in an effort to improve the iforms; NEMA, Kenya National Environmental Management authority. final effluent for irrigation. Biological oxygen demand and total Non-commercialTable 3. Comparison of 0.1mm sand filter filtrate with the standards recommended for suspended solids were significantly (<0.05) irrigation during dry season. higher than the compared standard for the filtrate from 0.1mm sand filter to be used in Parameters Mean±SE Recommended standards P-value irrigation. Biological oxygen demand in the BOD (mg/L) 33.33±0.33 ≤ 30 0.0049 filtrate recorded a mean of 33.33 mg/L COD (mg/L) 74.33±5.17 ≤100 0.9808 against recommended standard for irriga- tion of ≤30 mg/L while TSS in the 0.1 mm TSS (mg/L) 81.67±0.67 ≤30 <.0001 filtrate was 81.67 mg/L against ≤30 mg/L TC (cfu/100 mL) 960.0±11.55 ≤ 1000 0.9629 recommended for the filtrate to be used for irrigation. However, COD and TC obtained Table 4. Comparison of 0.05 mm sand filter filtrate with the standards recommended for in the 0.1 mm sand filter filtrate were not irrigation during dry season. significantly (>0.05) above the recommend- Parameters Mean±SE Recommended standards P-value ed standards for the filtrate to be used in irrigation. BOD (mg/L) 27.67±0.67 ≤30 0.9636 The quantity of BOD, COD, TSS and COD (mg/L) 62.33±1.45 ≤100 0.9993 TC obtained in the filtrate from 0.05 mm TSS (mg/L) 23.33±3.33 ≤30 0.9082 slow sand filter were significantly not (>0.05) higher than the compared standards TC (cfu/100 mL) 600.0±0 ≤1000 1.0000

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The two parameters TC and TSS ions react to provide more Biological Oxygen Demand and COD obtained in the filtrate from 0.05 mm slow leaving an excess of hydroxyl ions increas- were not treated to the recommended stan- sand filter were significantly lower (>0.05) ing the Ph of the wastewater.15 The genera- dard for irrigation during dry season this than the recommended standards for the fil- tion of hydrogen and hydroxyl ions during could be due to lack of dilution of the trate to be used for irrigation. The amount the process of wastewater treatment con- wastewater by direct rainfall to the open of TC in the filtrate was 400 cfu/100 mL tributed to the attainment of the recom- treatment ponds at BSTP which took place and TSS was 15 mg/L compared with the mended standards for the wastewater to be during wet season on top of conventional standards for irrigation of ≤1000 cfu/100 suitable for irrigation purposes. wastewater treatment process. These find- mL and ≤30 mg/L respectively. On contrary, TSS and TC in the ings concur with those of Kayima20 who Total coliforms and total suspended wastewater were not treated to the recom- attributed their relative higher values of solid in the filtrate obtained from mixture mended standards for irrigation during the BOD and COD in dry season than wet to (0.05 and 0.1 mm) sand filter were signifi- two seasons by BWTP. The lagging of TSS dilution of the stream by rain.21 in his study cantly lower (>0.05) than the recommended could be due to its increase at the trickling on seasonal variation on also standards for the filtrate to be used for irri- filter compared to its preceding stage of pri- concluded that the fewer amounts of COD gation. The amount of TC in the filtrate was mary pond rather than decreasing. The in rainy season than winter and summer was 440 cfu/100 mL and TSS was 26 mg/L com- droppings of the birds swimming at the sec- a result of more amount of water used by pared with the standards for irrigation of ondary and tertiary ponds at the treatment more/less occupants in a house during ≤1000 cfu/100 mL and ≤30 mg/L respec- plant would have contributed to increase of September and due to less dilution occurred tively (Tables 5-8). TC, making the plant inefficient.18,19 in greywater during January. Similarly in observed that from the drinking water pro- earlier studies by Mara22 they demonstrated duction stand point the presence of aquatic that the design parameters such as BOD in Discussion birds at the water reservoirs was associated oxidation ponds attain maximum values in with decreasing quality of water. The lack the hot season and minimum values in the Both the two wastewater treatment sys- of any physical instrument that can remove wet/cold season. tems involved in this study; Boundary the fine debris at the BWSTP might also The slow sand filters except the one Sewage Treatment Plant and the slow sand have contributed to the treatment plant no to withonly 0.1mm grain size improved the quality filtration treated their respective influent to achieve the irrigation standards during the of the wastewater to the level that can be either up to the standards recommended for two seasons. used for irrigation during both the dry and crop irrigation or reduced the amount of the parameter in the wastewater but failed to use achieve the standard for irrigation. Total dissolved solids and pH met the recommended standards for irrigation dur- Table 5. Comparison of mixture (0.01 mm and 0.05 mm) sand filter filtrate with the ing both dry and wet seasons for the treated standards recommended for irrigation during dry season. wastewater from Boundary Sewage Treatment Plant to be used for irrigation. Parameters Mean±SE Recommended standards P-value This attainment could be attributed to the BOD (mg/L) 28.33±0.33 ≤30 0.9811 sufficient treatment of the wastewater at the COD (mg/L) 70.00±0.58 ≤100 0.9998 various stages of primary pond, trickling fil- TSS (mg/L) 26.33 ± 0.33 30 0.9959 ter, sedimentation, secondary and tertiary ≤ ponds at the treatment plant. Denitrification TC (mg/L) 813.3 ± 3.33 ≤1000 0.9998 process could have contributed to the reduc- tion of TDS to the acceptable level for irri- Table 6. Comparison of the 0.1 mm slow sand filtrate with the standards recommended gation. passing through the process for irrigation during wet season. of denitrification was reduced to nitrous oxide and in turn nitrogen gas. Since nitro- Parameters Mean±SE Recommended standards P-value gen gas has low water solubility,Non-commercial it escapes TC (cfu/100 (mL) 706.7±3.33 ≤1000 0.9999 into the atmosphere as gas bubbles.15 The TSS (mg/L) 55.00±0 ≤30 <.0001 reduction of the amount of TDS in the wastewater to the standard suitable for the treated wastewater to be used for irrigation Table 7. Comparison of the 0.1 mm slow sand filtrate with the standards recommended also could be due to reduction of phosphate for irrigation during wet season. at the ponds through by accumulation of polyphosphate by microorganisms.16 The Parameters Mean±SE Recommended standards P-value achievement of pH was also due to the var- TC (cfu/100 mL) 400.0±0 ≤1000 1.0000 ious treatment processes at the various TSS (mg/L) 15.00±2.89 ≤30 0.9825 stages at the treatment plant. occurring in the at the bot- tom of the primary pond in BWTP results in Table 8. Comparison of the mixture slow and filtrate with the standards recommended converting organic load in the influent to for irrigation during wet season. methane and carbon dioxide and releasing some soluble organic into the water Parameters Mean±SE Recommended standards P-value column.17 The position of oxypause similar- TC (cfu/100 mL) 440.0±0 ≤1000 1.0000 ly changes as does the pH since at peak TSS (mg/L) 26.00±0.58 30 0.9899 algal activity carbonate and bicarbonate ≤

[Microbiology Research 2018; 9:7269] [page 17] Article wet seasons. The efficiency of the sand fil- Sci 2011;31:1-8. USA 1995. ters in improving the final effluent from the 2. Scott CA, Faruqui NI, Raschid-Sally L. 15. Mackne C, A, Casey P, Solomon treatment plant across the two seasons Wastewater use in irrigated agriculture: C. Trickling filters achieving filtration could be attributed to the various treatment Confronting the livelihood and environ- factsheet published by national small mechanisms in the sand filters. Several mental realities. CABI 2004;25. flows clearing house. 1998. mechanisms for the removal of particles, 3. Keraita B, Jiménez B, Drechsel P. 16. Prescott LM, Harley JP, Klein DA. microorganisms and organic matter exist in Extent and implications of agricultural Microorganisms in aquatic environ- slow sand filters have been documented. As reuse of untreated, partly treated and ments. 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