Waste Water Evaluation and Management Part 16 pot

Anaerobic batch co-digestion of cassava waste water and Swine dung The cassava waste water alone had the highest yield of biogas production 130 dm3/Total mass of slurry even though the

Waste Water:Treatment Options andits Associated Benefits 439

Fig 2 136L Capacity Metallic Prototype Biodigester

Experimental studies

The wastes were generally mixed with water in the ratio of 2:1 except in the cases where the wastewaters were used alone as control In such instances, the waste waters were used as they were without further dilution since the constituents were mainly water (93-95%) The digesters were charged up to ¾ level leaving ¼ head space for gas collection They were stirred thoroughly and on a daily basis throughout the retention period to ensure homogenous blend of the wastes and dispersion of microbes in the entire mixture Gas production measured as dm3/kg slurry or L/Total mass of slurry were obtained by downward displacement of water by the gas

Analyses of wastes

Physicochemical properties of the wastes such as ash, moisture, crude fibre contents, crude fat, crude nitrogen and protein contents, carbon, energy, total and volatile solids were generally determined for all the wastes using recognized laboratory procedures These properties inherent in the wastes determine and explain the behavior of the wastes during anaerobic digestion Biochemical analyses such as pH, ambient and influent temperatures were also monitored on the waste slurries as the digestion of the waste progressed Microbial analysis was also carried out to determine the microbial total viable counts (TVC) for the waste slurries at different periods during the digestion; at the point of charging the digester, at the point of flammability, at the peak of gas production and at the end of the retention period In some cases flammable gas composition from the different wastes were also analyzed

6 Results and discussion

The various results obtained during each of the studies are as itemized below:

1 Anaerobic batch co-digestion of cassava waste water and Swine dung

The cassava waste water alone had the highest yield of biogas production (130 dm3/Total mass of slurry) even though the gas produced was not flammable throughout the retention

period and therefore does not meet the desired need for cooking and lighting but would

however be okay for the purposes of ordinary treatment of the waste water The non

flammability of the gas produced was attributed to the acidic nature of the waste The

microbes that convert wastes to biogas are pH sensitive and survive optimally within the

pH range of 6.5-7.5 (Runion, 2009) It was observed that the fresh cassava waste water kills

plants in the farm However when subjected to anaerobic digestion for a period of 30 days it

can then be used in the farms as a good organic fertilizer for agriculture The CW and SD

(cassava waste water and swine dung blend) had a lower yield of 120L/total mass slurry;

however it commenced flammability on the 10th day The swine alone had a yield of 123

L/Total mass slurry and commenced flammability on the 6th day The results showed that the

animal waste had a positive effect on the cassava waste water since the CW on its own did not

produce flammable gas There was also attendant reduction in the foul odour of the waste

after the digestion showing that the anaerobic digestion killed most of the pathogens

responsible for the foul odour Fig 3 shows the daily biogas production for the period, while

Table 1 shows the lag period, cumulative and mean volume of gas productions The lag period

is the period from charging of the digester to onset of gas flammability (Ofoefule et al., 2010)

Fig 3 Daily biogas production

Lag period (days) Nil 5 9

Cumulative gas yield (L/ total mass of slurry) 130.25 122.55 119.90

Mean gas yield (L/ total mass of slurry) 4.20±1.32 3.95±2.01 3.87±1.80

Table 1 Lag period, Cumulative and mean volume of gas production of the pure wastes and

blend

2 Effect of Abattoir cow liquor waste on biogas yield of some Agro-Industrial wastes

The results in this study showed that the cow liquor waste and cassava waste water blend

(CLW: CW) did not flame throughout the retention period as a result of the acidic nature of

the combined waste (pH=3.3) The carbonated soft drink sludge that commenced flammable

biogas production on the 9th day stopped after one and half weeks as a result of the drop in

pH from 5.68 to 5.20 The reduction in pH killed the microbes responsible for converting the

Waste Water:Treatment Options andits Associated Benefits 441

waste to biogas However the CLW: BS (cow liquor waste: brewery spent grain) had the

shortest onset of gas flammability and highest cumulative gas yield of 613.2 L/TMS (Table

2) Fig 4 shows the daily biogas production (Uzodinma and Ofoefule, 2008)

Lag period (days) 20 8 Nil 6 9 8

Cumulative gas yield (L/TMS) 183.6 177.50 Nil 613.2 394.2 87.4

Mean Volume of gas yield

(L/TMS) 7.34 7.10 Nil 24.53 8.23 2.54

Table 2 Lag periods, cumulative and mean volume of gas yield for single organic wastes

and CLW blends

0 5 10 15 20 25 30 35 40

Fig 4 Daily biogas yield

3 Preliminary studies on biogas production from blends of palm oil sludge with some

Agro-based wastes

The palm oil sludge (POS) in this study could not produce quantifiable gas within the 25

days retention period used for the experiment However when combined with brewery

spent grain (SG), carbonated soft drink sludge (SL) and cassava waste water (CW),

reasonable quantities of biogas were produced which flamed after some lag periods as

shown in Table 3 The POS: CW had the highest yield of biogas followed by the POS: SG

while the least yield came from the POS:SL The better yield of POS: CW over the others

could be accounted for by the fact that the CW and others were allowed to be partially

decomposed for a period of two months to increase their pH level, since in their fresh state

they were found to be acidic This resulted in the cassava waste water giving a better yield

of biogas Analysis of their flammable gas composition showed that POS: CW and POS: SL

gave higher methane contents than POS: SG (Table 4) Fig 5 shows the Daily biogas

production (Uzodinma et al., 2007a)

Lag period (days) 10 8 15

Cumulative gas yield (L) 312 394.2 87.4

Mean volume of gas yield (L) 12.5 15.8 3.5

Table 3 lag periods, cumulative and mean volume of gas yield for POS blends

Fig 5 Daily biogas yield for POS blends

4 Energy generation from microbial conversion of Treated cassava waste water from

garri processing industry

In this study, cassava waste water (CW) was treated with some other wastes to improve its

pH level before digesting it The waste used included; palm oil sludge (POS), powdered rice

husk (RH) and pig dung (PD) The results showed that not only was the pH increased, the

physicochemical properties also improved, which translated to higher biogas yields The

CW: RH gave the highest yield while the CW: PD followed with the shortest lag period of 4

days (Table 5) The higher yield of CW: RH was attributed to the fact that the rice husk was

pre-decayed for about 1 month, and as a result had accumulated some microbes that aided

in the faster digestion The shortest lag period of CW: PD was explained by the fact that

swine dung is a rumen animal, having the natural flora that are responsible for biogas

production in its gut, aiding the fastest onset of gas flammability Fig 6 shows the Daily

biogas production (Uzodinma et al., 2007b)

Lag period (Days 8 6 4

Cumulative volume of gas Production (L/TMS) 394.20 481.30 432.00

Mean volume of gas production (L/TMS) 15.77 19.30 17.30

Table 5 Lag Period, Cumulative and Mean volume of biogas production

Waste Water:Treatment Options andits Associated Benefits 443

Fig 6 Daily biogas production

Socio-Economic Benefits of Waste Water Treatment

Apart from reduction in environmental pollution from the treatment of waste waters, new demands for agricultural products arising from increased biomass usage would impact on the social-economic life of the populace especially when anaerobic digestion process of waste water treatment option is undertaken Social issues such as employment generation, and poverty reduction especially for the developing countries would be addressed through this technology as a result of expanded economic activities across the real sector of the economy encompassing agriculture, manufacturing and exports These would enhance people’s ability to develop economic activities designated to reduce poverty particularly for the rural communities Conversion of these biodegradable waste waters (both domestic and industrial) into biogas would result in cleaner air as well as efficient waste management system, improving the sanitary conditions of the urban environment This will lead to socio-economic benefits with regard to health, income and security of the eco-system threatened

by adverse climatic alterations (Ofoefule et al., 2009)

5 Conclusion

The results of these studies have shown that the waste waters/ slurries which are pollutants

in the areas where they are processed can be sources of useful energy and organic fertilizers

by subjecting them to anaerobic digestion for biogas production The studies further revealed that most of these waste waters on their own are not capable of effective and efficient biogas production since they are mostly found to be acidic in their fresh states They therefore need to be co-digested with other better producing wastes like animal wastes

to enhance their flammable biogas production capabilities The anaerobic digestion process

of these waste waters is expected to be a source of waste management and pollution control

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23 Agricultural Dairy Wastewaters

Owen Fenton, Mark G Healy, Raymond B Brennan, Ana Joao Serrenho,

Stan T.J Lalor, Daire O hUallacháin and Karl G Richards

Teagasc, Environmental Research Centre, Wexford

National University of Ireland, Galway

Rep of Ireland

1 Introduction

In Ireland, farming is an important national industry that involves approximately 270,000 people, 6.191 million cattle, 4.257 million sheep, 1.678 million pigs and 10.7 million poultry (CSO, 2006) Agriculture utilizes 64% of Ireland’s land area (Fingleton and Cushion, 1999),

of which 91% is devoted to grass, silage and hay, and rough grazing (DAFF, 2003) based rearing of cattle and sheep dominates the industry (EPA, 2004) Livestock production

Grass-is associated with external inputs of nutrients Phosphorus (P) surpluses accumulate in the soil (Culleton et al., 2000) and contribute to P loss to surface and groundwater (Tunney, 1990; Regan et al., 2010) Elevated soil P status has been identified as one of the dominant P pressures in Ireland (Tunney et al., 2000) Schulte et al (2010) showed that it may take many years for elevated soil P concentrations to be reduced to agronomically and environmentally optimum levels The extent of these delays was predominantly related to the relative annual P-balance (P balance relative to total P reserves) While the onset of reductions in excessive soil P levels may be observed within five years, this reduction is a slow process and may take years to decades to be completed

Agricultural wastes and in particular dairy slurry and dirty water are discussed in this chapter However, while the term ‘waste’ is commonly used for these materials, it is an unfortunate label, as it suggests that the materials have no further use and are merely a nuisance by-product of farming systems that must be managed However, given the high nutrient contents of these materials, it is far more appropriate for them to be considered as organic fertilizers, and as such being a valuable commodity for the farmer With higher and more volatile chemical fertilizer prices in recent years, the fertilizer replacement value in economic terms of these materials is increasing Therefore, the management of agricultural

‘wastes’ in a manner that maximises the nutrient recovery and fertilizer value to crops should be a priority within any management plan for these materials

Nutrient contents and various research areas regarding management, remediation and control of such nutrients to prevent losses to the environment are discussed The Surface Water Directive, 75/440/EEC (EEC, 1975), the Groundwater Directive, 80/68/EEC (EEC, 1980), the Drinking Water Directive, 98/83/EC (EC, 1998), the Nitrates Directive, 91/676/EEC (EEC, 1991(a)) and the Urban Wastewater Directive, 91/271/EEC (EEC, 1991(b)), combined with recent proceedings taken against the Irish State by the EU Commission alleging non-implementation of some aspects of the directives, has focused

considerable attention on the environmentally-safe disposal of agricultural wastewaters in Ireland To address these directives, the WFD (2000/60/EC, 2000) came into force on 22ndDecember, 2000 and was transposed into Irish legislation by the European Communities (Water Policy) Regulations 2003 on the 22nd December, 2003 Eight “River Basin Districts” (RBD) were established in Ireland, north and south, with the aim of achieving “good status”

in all surface and groundwater by 2015 The WFD will bring about major changes in the regulation and management of Europe's water resources Major changes include:

• A requirement for the preparation of integrated catchment management plans, with remits extending over point and non-point pollution, water abstraction and land use;

• The introduction of an EU-wide target of "good ecological status" for all surface and groundwater, except where exemptions for "heavily-modified" water bodies are granted Programmes of measures (POM) must be put in place to protect groundwater and surface water while being efficient and cost-effective POM to achieve at least

“good ecological status” must be implemented by the agricultural sector by 2012 In Ireland the Nitrates Directive is the main POM in place At present, a strategy exists within Europe to restore the “good ecological status” of surface and groundwater It focuses on reducing nutrient pressures to prevent further nutrient loss to surface and groundwater However, intensification of agriculture poses a challenge to the sustainable management of soils, water resources, and biodiversity N losses from agricultural areas can contribute to ground- and surface water pollution (Stark and Richards, 2008; Humphreys et al., 2008)

Results from a Water4all project suggest that regulation alone will not achieve sufficient reduction in water quality as nitrate builds up in soils and the long residence time of groundwater in aquifers needs a more immediate solution (Water4all, 2005; Hiscock et al., 2007) Therefore, remediation (nitrogen - N) and control (phosphorus – P) technologies must

be an integral part of the process for point and diffuse pollution from historic or future incidental nutrient losses Solutions developed must be integrated efforts within a catchment or river basin

Good Agricultural Practice Regulations under The Nitrates Directive (European Council, 1991) is currently the main mitigation measure in place within the agricultural sector to achieve the goals of the WFD These regulations came into effect in the Republic of Ireland

in 2006 under Statutory Instrument (S.I) 788 of 2005, and subsequently under S.I 378 of 2006, S.I 101 of 2009 and S.I 610 of 2010 The Nitrates Directive sets limits on stocking rates on farms in terms of the quantity of N from livestock manure that can be applied mechanically

or directly deposited by grazing livestock on agricultural land A limit of 170 kg N ha-1 year

-1 from livestock manure was set However, the EU Nitrates Committee approved Ireland’s application for a derogation of this limit to allow grassland-based (mostly dairy) farmers to operate at up to 250 kg N ha-1 year-1 from livestock manures, with the understanding that this derogation will not impinge on meeting the requirements of the Nitrates Directive The current average stocking density on dairy farms is 1.81 livestock units (LU) ha-1

The “Good Agricultural Practice for the Protection of Waters” regulation, S.I 778 of 2005 (Anon, 2005), came into effect on February 1st 2006 The most recent revision of the regulation was published in 2010 (Anon, 2010) It constrains the use of P and N fertilizers, ploughing periods and supports derogation on livestock intensity In particular it regulates farmyard and nutrient management, but also examines prevention of water pollution from fertilizers and certain activities The linkage between source and pathway can be broken if pollutants remain within farm boundaries and are not discharging to drainage channels,

Agricultural Dairy Wastewaters 449 subsurface drainage systems, or entering streams or open waterways within farm boundaries These regulations also place restrictions on land spreading of agricultural wastes This strategy looks at present loss and future loss prevention There are no guidelines in place for the remediation or control of contaminated discharges to surface and/or groundwater or future discharges due to incidental losses Traditionally, agricultural wastes are managed by land spreading Following land spreading, the recharge rate, the time of year of application, the hydraulic conductivity of the soil, the depth of soil

to the water table and/or bedrock, and the concentration of nutrients and suspended sediment in the wastewater (dirty water and any discharge containing nutrients) are some

of the defining parameters that determine nitrate movement through the soil to the watertable The maximum instantaneous rate of application is 5 mm per hour and the quantity applied should not exceed 50 m3 per hectare per application (ADAS, 1985; 1994; DAFF, 1996) and these recommendations are present within best farm management practices Infiltration depth of irrigated water and rainfall may be estimated when the annual effective drainage, number of effective drainage days, effective porosity, annual precipitation, and the hydraulic load of the irrigator are known (Fenton et al., 2009(b)) This data may then be combined with watertable data to examine if excess nutrients recharge to groundwater within a specific time frame

2 Agricultural dairy wastes

2.1 Types of dairy wastes and nutrient content

In a grassland system, the N recovery rate of dairy slurry is highly variable due to variations

in slurry composition, application methods, spreading rates, soil and climatic conditions and slurry N mineralisation rates (Schröder, 2005) In Ireland, approximately 80% of manures produced in winter are managed as slurries containing 70 g kg-1 dry matter, 3.6 g

kg-1 total N (TN) and 0.6 g kg-1 total P (TP) (Lalor et al., 2010(a)) About 50% of the TN is in ammoniacal form and has the potential to be volatilised as ammonia during storage and following land spreading Estimated organic managed waste generation for Ireland is presented in Table 1

Waste Category Waste Generation

Tonnes wet weight % Cattle manure and slurry 36,443,603 60.6Water (dairy only) 18,377,550 30.5Pig slurry 2,431,819 4.0 Silage effluent 1,139,231 1.9 Poultry litter 172,435 0.3 Sheep manure 1,336,336 2.2 Spent mushroom compost 274,050 0.5

Total 60,170,025 Table 1 Estimated agricultural organic managed waste generation in 2001 (EPA, 2004a) Great variation in the nutrient content of dairy slurry exists depending on feed type, age of sample when tested, age of the animal and how the effluent is stored and managed (Smith and Chambers, 1993) Seasonal differences in nutrient contents also exist (Demanet et al., 1999) Tables of published slurry nutrient contents in Europe exist (see MAFF, 2000) Such

values are similar to South American dairy slurry concentrations found by Salazar et al (2007) Some dairy slurry concentrations for undigested and digested samples are presented

in Table 2 These tend to be similar to other nutrient contents across Europe found by Villar

et al (1979); Scotford et al (1998(ab)) and Provolo and Martínez-Suller (2007) In Ireland, dirty water is generated from dairy parlour water and machine washings, precipitation and water from concreted holding yards (Photo 1) Average dirty water production per cow is 49

L-1 day-1 Although dilute, dirty water has sufficient nutrients to give rise to eutrophication if lost to a waterbody through runoff or excess infiltration Implementation of current legislation requires separation of faecal matter and water, thus diminishing the nutrient content of dirty water for land application (Photo 1) As the nutrient content is reduced and storage and water charges are high, an alternative solution to dirty water management is remediation and re-use for washing yards (Fenton et al., 2009) A number of papers have reported the chemical composition of dirty water from dairy farms (ADAS, 1994; Cumby, 1999; Ryan, 2006; Fenton et al., 2009(a);Minogue et al., 2010) Table 3 presents a range of nutrient contents available in dirty water from a number of studies Minogue et al (2010) and Cumby (1999) report higher mean TN nutrient figures for 20 farms in England and Wales of 580±487 mg TN L-1 Martínez-Suller et al (2010(b)) reviewed the composition of dirty water in the literature including others not mentioned in Table 3

Photo 1 Dirty water generation: wash down high volume low pressure hose and drainage channel for speeding up washing after milking (Source: www.teagasc.ie)

Prediction of the nutrient content of agricultural waste waters would help farmers to more accurately calculate the nutrient fertiliser replacement value of the landspread materials and the additional fertiliser requirements for their crops Martínez-Suller et al (2010(a)) suggest that dry matter content or electrical conductivity are rapid, cheap methods to estimate the nutrient content of waste waters and manures

2.2 Faecal microorganisms

Agricultural wastes not only pose a threat to waterbodies, a second major concern is the presence of pathogenic and/or antibiotic resistant bacteria in animal wastes (Sapkota et al., 2007) and the threat to human health If properly handled and treated, manure is an effective and safe fertiliser However, if untreated or improperly treated, manure may become a source of pathogens that may contaminate soil, food-stuffs, and water bodies (Vanotti et al., 2007) Animal manures are known to contain pathogenic bacteria, viruses and parasites (Pell, 1997) The contamination of surface waters with pathogenic micro-organisms transported from fields to which livestock slurries and manure have been applied is a serious environmental concern as it may lead to humans being exposed to such micro-organisms via drinking water (Skerrett and Holland, 2000); bathing waters (Baudart et al., 2000); and water used for the irrigation of ready to eat foods (Tyrel, 1999) A recent study

Agricultural Dairy Wastewaters 451

Table 3 Dairy dirty water nutrient results from various studies in U.K and Ireland

Based on new data and Martínez-Suller et al., 2010(b) All units in mg L-1

Agricultural Dairy Wastewaters 453 (Venglovsky et al., 2009) has shown that animal manure contributes significantly to pathogen loading of soil and consequently runoff to waterways Furthermore, a recent report by the EPA in Ireland (Lucey, 2009) highlighted land-spreading of manure or slurry

as one of the main sources of microbial pathogens in groundwater Additionally, a report by the Food Safety Authority of Ireland (FSAI, 2008) stated that ‘there is potential for the transfer of pathogens to food and water as a result of land-spreading of organic agricultural material’

Research from New Zealand, shows that dirty water contains faecal micro-organisms, which originate from dairy cattle excreta Researchers such as Aislabie et al (2001); McLeod et al (2003) and Donnison and Ross (2003) have shown transfer of bacterial indicators, faecal

coliforms and Campylobacter jejuni through soil The Pathogen Transmission Routes Research

Programme in New Zealand showed that significant faeces contamination arose through the deposition of faeces by grazing animals with access to waterways Fencing and implementation of buffer strips were recommended as mitigation measures to prevent such losses (Collins et al., 2007) Presence of faecal indicator organisms is used to identify waters

impacted by faecal matter from mammals Indicators of faecal contamination such as E coli

are widely used as they are faecally specific and believed to not survive for more than 4

months post excretion (Jamieson et al., 2002) Recent research has shown that E coli can

survive for long periods of time in temperate soils (Brennan et al., 2010) and contribute to

high detections in drainage waters from agricultural soils E coli were particularly

associated with poorly drained soils due to the greater persistence of preferential flow

channels and anaerobic micro-sites where they might survive Thus the presence of E coli in

waters may not indicate recent contamination by faecal matter but could be due to historical pathogen deposition Many treatment systems may be used to treat livestock waste and remove or decrease viral, bacterial and eukaryotic pathogens Examples include bio-gas producing anaerobic digestion, composting, aeration, storage under a variety of redox conditions, and anoxic lagoons, all of which have been reviewed by Topp et al (2009)

2.3 Current management practices for agricultural waste waters

The Nitrates Directive and rising costs are now forcing better use of nutrients in slurry Research in the U.K (Misselbrook et al., 1996; 2002; Smith and Chambers, 1993; Smith et al., 2000) includes improving N recovery from slurry by examining the effect of spreading method and timing, and reducing ammonia (NH3) losses from slurry by evaluating splash-plate versus alternative techniques such as trailing shoe or trailing hose slurry application methods The average abatement of these methods varies and differs when grassland or arable application are considered (Smith and Misselbrook, 2000; Misselbrook et al., 2002) Present research in Ireland follows similar patterns (Ryan, 2005) Ammonia emissions with respect to trailing shoe versus splash-plate and subsequent N uptake by the sward are being investigated in Irish grasslands (Lalor and Schulte, 2008) Farm management strategies aimed at prevention of nutrient loss to water have recently been reviewed by Schulte (2006) The Nitrates Directive regulations impose limits to N and P inputs onto livestock and tillage farms Cattle and dairy farming systems are required to make more efficient use of nutrients International experience suggests that significant gains in nutrient efficiency can

be made by increasing the utilisation of N in slurry Lalor (2010(b)) suggested N-utilisation efficiencies from slurry as low as 5% under existing practices, whereas international literature suggests that there is scope to raise efficiencies to 40-80% Despite the relatively low utilisation in practice, the Nitrates regulations set a nitrogen fertilizer replacement value