NZ721286B - Improvements in and relating to animal effluent treatment system - Google Patents

Abstract

use of a clarifying composition comprising a coagulant; for clarifying a liquid animal effluent wherein the coagulant is a metallic salt compound and the active ingredient are metal ions present in the amount of substantially between 1mg – 1000mg per litre of liquid effluent to be clarified.

Description

James & Wells ref: 303389/14 JV IMPROVEMENTS IN AND RELATING TO ANIMAL EFFLUENT TREATMENT SYSTEM TECHNICAL FIELD The present invention relates to improvements in and relating to animal effluent treatment systems. In particular, an animal effluent treatment system, and compositions and components therefor, which can produce recycled water therefrom, which is clean enough to be used on on- farm applications.

BACKGROUND ART The present invention will now primarily for ease of reference be described in relation to a dairy farm effluent treatment system. However, it is envisaged the present invention may well have application to other sources of animal effluent so any such discussion should not necessarily be seen as limiting.

Animal effluent on dairy farms presents a number of well-known critical problems which include: - the high nitrogen content of effluent which can lead to environmental damage if nitrogen leaching and/or runoff occurs following application of effluent to soil; - the high phosphorus concentration of effluent which can lead to environmental damage if the phosphorus is lost in leaching and/or runoff following application to soil; - the high microbial content (e.g. E. coli) of effluent which can lead to environmental damage and health risks if the microbes are lost in leaching and/or runoff following application to soil; - the high volume of water required to wash dairy yards including milking platforms; - the loss of nitrogen to the atmosphere due to volatilization and/or denitrification, which is a loss of nutrient and leads to environmental damage, e.g. contributing to global warming.

Whilst animal effluent treatment systems are known such as that disclosed in such a system requires the introduction of additional water as part of the separation of solids from the liquid to create a clear liquid phase. It would be useful if a system could be devised which did not rely on additional water to be introduced and/or could recycle water to reduce the overall on farm water usage.

Furthermore, it would also be advantageous if there could be provided one or more of the following: James & Wells ref: 303389/14 JV - an animal effluent treatment system which costs significantly less than existing systems; - an animal effluent treatment system which can be retrofitted into existing effluent capture/treatment systems; - an animal effluent treatment system which used chemicals which are inexpensive and most importantly safe for humans and animals and the environment; - an animal effluent treatment system that could be used to treat effluent at low temperatures during autumn-winter-spring (i.e. substantially 1 ⁰C – 17 ⁰C); - an animal effluent treatment system that can be used across a range of effluent pH values; - an animal effluent treatment system that can reduce phosphorous from the treated liquid effluent; - an animal effluent treatment system that can reduce microbial components (e.g. E. coli) from the treated liquid effluent; - an effluent treatment system that retains the nitrogen in the treated liquid and reduces losses to the environment; - a treated liquid effluent sludge that can be applied to soil as a fertilizer; - an animal effluent treatment system which can re-use wash water and minimize water wastage.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

James & Wells ref: 303389/14 JV DEFINITIONS The terms ‘liquid farm effluent’ and ‘liquid animal effluent’ both refer to animal urine and fecal matter which has been rinsed from a yard or other animal containment area and contains a high liquid (i.e. water) content as well as solid matter mixed therein.

The term ‘sludge’ as used herein refers to the thicker wet viscous component derived from the treatment of animal effluent. The sludge has a visibly noticeable higher solid content than the treated liquid effluent.

The term ‘alkalinity’ as used herein refers to a chemical compound (liquid or solid) which can increase the pH of a solution (i.e. can neutralize an acid). In general the term ‘alkalinity’ refers to a compound which provides hydroxide ions when in aqueous solution.

DISCLOSURE OF THE INVENTION According to a first aspect of the present invention there is provided a use of a clarifying composition comprising: - a coagulant; for clarifying a liquid animal effluent wherein the coagulant is a metallic salt compound and the active ingredient are metal ions present in the amount of substantially between 1mg – 1000mg per litre of liquid effluent to be clarified.

According to a second aspect of the present invention there is provided use of a liquid animal effluent clarifying composition substantially as described herein wherein the coagulant is selected from ferric chloride, ferric sulphate, or polyferric sulphate or aluminum sulphate.

Most preferably, the coagulant may be ferric sulphate or polyferric sulphate, as this will add a source of sulphur to the treated liquid and sludge thus, supplying a plant nutrient to the treated liquid and sludge which can be subsequently delivered to the soil.

According to a third aspect of the present invention there is provided a single tank liquid farm effluent treatment system comprising: - a source of liquid animal effluent (LAE); - a treatment tank connected to said source of LAE and which captures said LAE; - a sludge removal outlet on said treatment tank connected to a sludge containment receptacle; - a source of a coagulant connected to said treatment tank; James & Wells ref: 303389/14 JV - an (optional) source of a coagulant aid connected to said treatment tank; - an (optional) source of alkalinity connected to said treatment tank; - an (optional) source of a disinfectant connected to said treatment tank; - a delivery mechanism associated with each of the sources of coagulant, coagulant aid, hydroxide ions and disinfectant; - a turbidity sensor for measuring turbidity and relaying information to a controller which is associated with the coagulant delivery system; - a pH sensor for measuring pH and relaying information to a controller which is associated with the coagulant and alkali delivery system; - a cleaned water outlet on said treatment tank which is connected to one or more on-farm water systems able to utilise cleaned water. The source of alkalinity and source of disinfectant may in some embodiments, be one and the same. In one such embodiment, sodium hypochlorite (or calcium hypochlorite) is both the disinfectant and the alkali.

According to a fourth aspect of the present invention there is provided a method of treating liquid animal effluent to produce cleaned water including the steps of: a) capturing liquid effluent run off from an animal containment area in a treatment tank; b) optionally, allowing the large particles to settle in the tank for about 30 to 60 minutes before this ‘large particle sludge’ is discharged from the base of the tank to the effluent collection zone. c) measuring the turbidity and pH of the effluent (or remaining effluent); d) treating the captured effluent (or remaining effluent) directly with a coagulant; e) measuring turbidity of the liquid phase of the effluent in the treatment tank; f) repeating step d) if the turbidity is above a pre-determined value; g) removing the liquid phase, from the tank, once turbidity of liquid phase equals less than a pre-determined value at step e); h) directing the solid/sludge phase to a collection zone.

According to a fifth aspect of the present invention there is provided a method of treating animal effluent including the steps of: a) first, adding a coagulant aid and/or alkali and/or disinfectant (e.g. sodium hypochlorite) to the animal effluent to be treated as pre-treatment; and James & Wells ref: 303389/14 JV b) secondly, adding a coagulant to the pre-treated animal effluent of step a).

According to a sixth aspect of the present invention there is provided a method of treating animal effluent including the steps of: a) first, adding a coagulant to the animal effluent to be treated as pre-treatment; and b) secondly, adding a coagulant aid and/or alkali and/or disinfectant (e.g. sodium hypochlorite) to the pre-treated animal effluent of step a).

BRIEF DESCRIPTION OF THE DRAWINGS Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 shows how the turbidity reduces upon addition of Ferric chloride to liquid dairy farm effluent; Figure 2 shows how the amount of ferric chloride can be optimised to treat the solids content of the effluent; Figure 3 shows how ferric chloride is effective at low temperature; Figure 4 shows the ferric chloride treatment system is effective over a wide range of effluent pH values (typical pH 5.5-8.5); Figure 5 shows how the ferric chloride treatment system can be used to reduce turbidity over a wide range of milk content in the effluent; Figure 6 shows how the treatment system of the present invention can remove >99% of Phosphorous; Figure 7 shows how the treatment system of the present invention can remove >98% of Turbidity, E. coli, Total Phosphorous (TP) and Dissolved Reactive Phosphate (DRP) using polyferric sulphate as coagulant; Figure 8 shows how the treatment system of the present invention can remove 99% of indicator bacteria (E. coli) from effluents with a range of turbidity values.

Figure 9 shows how ferric chloride can reduce pH and ammonia volatilisation; Figure 10 shows how by keeping the pH<7 ammonia volatilisation remains low even at high N concentrations; James & Wells ref: 303389/14 JV Figure 11 shows how ferric chloride can be added in multiple doses; Figure 12 shows how clean recycled effluent liquid can be used multiple times to wash the yard since the reduction in turbidity using the coagulant formula of the present invention is unaffected by recycling (i.e. always >99%); Figure 13 shows a single tank dairy farm effluent treatment system according to one preferred embodiment of the present invention; and Figure 14 shows the treatment system according to a preferred embodiment of one aspect of the present invention.

BEST MODES AND ILLUSTRATIVES EXAMPLES A series of standard jar test experiments were conducted to determine the effect of adding a coagulant, alkali, and coagulant aid to treat liquid animal effluent collected from a farm. The initial turbidity (or solids content) of the effluent was measured and one litre of effluent was used in each jar test. The effluent in the jar was mixed using the standard jar test equipment whilst one or more of the following sources of alkalinity (calcium oxide, calcium hydroxide, agricultural lime and/or bleach) was added to the effluent. A range of rates of these sources of alkalinity and/or coagulant aid were used (as shown in Figures 5, 6, 9 and 11 where the units on the x-axis are g/L of effluent). Immediately after those additions, an appropriate amount of ferric chloride or ferric sulphate or polyferric sulphate was added (the amount added depended on the initial turbidity (solids content) of the effluent (rates are shown in Figures 1, 2, 9, and 11 where the units are mg Fe/L of effluent). A range of mixing rates and times were used and optimized at 200 rpm for 2 minutes. The treated effluent was then allowed to settle for one hour before samples of the supernatant liquid and the sludge were collected for analysis. The effect of the treatment on key parameter values (e.g. turbidity, phosphorus, E. coli etc) was then compared against the original values in the untreated effluent. This comparison enabled quantification of the effectiveness of the treatment on the liquid effluent (i.e. percentage reductions in each parameter value achieved by the treatment).

In particular, in relation to: Figure 1, the y-axis shows the turbidity (i.e. NTU) value as affected by the rate of coagulant addition (i.e. mg Fe/L of effluent) (as shown on the x-axis). The different coloured lines on the graph represent the starting NTU value of each specific effluent tested, as shown by the first data point on the y-axis (in addition, the coloured legend on the right hand side of the figure shows the starting NTU values of each effluent, ranging from 500 to 2500).

James & Wells ref: 303389/14 JV Figure 2, the y-axis shows the percentage reduction in turbidity (%) for each treatment. Each ‘group’ of treatments on the x-axis represent the original turbidity NTU value of the effluent (i.e. 500, 1000, 1500, 2000, 2500). The rate of coagulant added is shown by the different colour of each vertical histogram bar (i.e. 100, 150, 200, 250 mg Fe/L of effluent). For example, the first group of four histogram bars represent the turbidity reduction for effluent that had a starting NTU value of 500. The effect of the addition of 100 mg Fe/L effluent (blue histogram bar) is shown on the y-axis as being less than 98% and this is labelled as ‘too low’.

Figure 3, the y-axis shows the percentage reduction in turbidity (%) for effluent at two different temperatures (17 °C and 5 °C) when treated with the ferric coagulant, hydrated lime and agricultural lime. The temperature of each effluent is shown within each vertical histogram bar and on the x-axis.

Figure 4, the y-axis shows the percentage reduction in turbidity (%) achieved with ferric chloride over a range of effluent pH values from pH 8.6 down to 5 (pH is shown on the x-axis).

Figure 5, the y-axis shows the percentage reduction in turbidity (%) when the ferric coagulant is added to effluent with a range of different milk contents. The amount of milk in the effluent (i.e. ml of milk per litre of effluent) is shown by a different colour for each histogram bar; as shown in the coloured legend at the right hand side of the figure (ranging from 0 to 10 ml of milk per litre of effluent.) The x-axis shows six groups of treatments (i.e. the first group of seven coloured histogram bars represents the turbidity reduction when 200 mg Fe/L effluent is added plus 0.2 g of agricultural lime added as a coagulant aid).

Figure 6, the y-axis shows the percentage removal of phosphorus from the supernatant (i.e. the ‘cleaned’ effluent liquid) when the effluent was treated with the ferric coagulant and agricultural lime (coagulant aid) at the different rates shown on the x-axis. For example, the first vertical bar shows the percentage removal of phosphorus from the supernatant when the ferric coagulant is added at a rate of 250 mg Fe/L of effluent, plus 0.2 g of agricultural lime per litre of effluent.

Figure 7, the y-axis shows the percentage reduction of each parameter shown on the x-axis (i.e. Turbidity, E. Coli, Total Phosphorus (TP), and Dissolved Reactive Phosphate (DRP)) when polyferric sulphate is used as the coagulant.

Figure 8, the y-axis shows the percentage reduction in E. Coli in both the ‘Supernatant’ and ‘Sludge’ when the effluent is treated with the ferric coagulant. The labels on the x-axis describe the original turbidity (NTU) value of the effluent and whether the data relates to the ‘supernatant’ or sludge’.

Figure 9, the y-axis shows the pH value of the original effluent and the pH value of the ‘supernatant’ after treatment with the ferric chloride coagulant. The different coloured lines on the graph represent the rate of ferric chloride (mg Fe/L) and rate of agricultural lime used (2 or James & Wells ref: 303389/14 JV 4 g/L) (the colour coding for the rate is also shown in the legend on the right hand side of the figure). The x-axis shows the rate of hydrated lime (g/L) added in addition to the ferric chloride and agricultural lime. The small ‘inserted graph’ in the centre of the figure shows the ratio of ammonium (NH ) to ammonia (NH ) at different solution pH values.

Figure 10, the y-axis shows the percentage ammonia volatilisation that occurs from the supernatant at a range of solution pH values, ranging from pH 5.5 to 7.0 (as shown in the legend on the right hand side of the figure). The x-axis shows the initial effluent concentration of ammonium (mg N/L). The small ‘inserted graph is the same as that in Figure 9.

Figure 11, y-axis shows the percentage reduction in turbidity (%) when the ferric coagulant is added in multiple doses (as described in the legend at the top of the figure). There are 4 replicate values shown as histogram bars and a mean value shown as the last histogram bar.

Figure 12, the y-axis shows the percentage reduction in turbidity (NTU) when the ‘cleaned’ supernatant is ‘recycled’ multiple times with effluent sludge. The x-axis shows the number of recycling events (or runs).

In relation to Figure 13 there is shown a single tank treatment liquid farm effluent (LFE) system 1 which has a treatment tank 2 into which LFE is directed from a source of LFE, namely in this instance, a milking platform and associated yard (not shown) after each wash down as shown by arrow 3. The tank 2 has a stirrer 4 located therein. Optionally the LFE is allowed to settle for about 30 – 60 minutes before the large particle sludge is discharged from the bottom of the tank to a collection zone.

Added, in the first instance, to the LFE collected in the tank 2, from an optional source of an alkali and/or detergent (not shown) via a delivery mechanism in the form of pump (not shown) is NaOCl as shown by arrow 5. Then from a source of coagulant (not shown) a coagulant in the form of ferric sulphate or polyferric sulphate shown by arrow 6 is added to the tank 2 via a delivery mechanism in the form of a pump (not shown).

The tank 2 also has a sludge exit port 8 and an outlet in the form of a cleaned water port 9.

The tank 2 also has a turbidity sensor (not shown) which senses turbidity and a pH sensor both of which feed this turbidity and pH information through to a controller in the form of a PLU (not shown) which assesses the turbidity and pH information and controls the aforementioned pumps to deliver the coagulant, alkalinity, and/or disinfectant to the tank 2. The amount of alkalinity added depended on the turbidity value, initial pH (alkalinity value) and /or the amount of coagulant required to treat the effluent. The greater the amount of turbidity and the greater the pH the greater the amount of ferric salt (coagulant) required. The amount of alkalinity delivered could be controlled by a pH sensor also connected to the PLU which then operates the pump associated with the source of alkalinity to deliver the correct amount of alkalinity to James & Wells ref: 303389/14 JV bring the pH into the desired range. However, typically the amount of coagulant added tends to bring the pH into the desired range.

The amount of disinfectant delivered is dependent on the size of the tank 2 and amount of LFE held within the tank when treatment process begins.

In relation to Figure 14 there is shown a liquid animal effluent treatment system 100. The system 100 has a yard 101 on which dairy cows are held before being milked. When the yard is washed down the LAE is moved via the existing effluent pump (not shown) to an existing sump 102. The heavy solids content of the LAE is removed by an existing solids separator 103 before passing the LAE to a treatment tank 104. The tank 104 via pumps (not shown) receives: - coagulant in the form of ferric chloride or ferric sulphate is added from a source of coagulant 105; - an alkali in the form of hydrated lime is added from a source of alkali 107.; - optionally, disinfectant/alkali in the form of Sodium hypochlorite (or calcium hypochlorite) is added from a source of disinfectant/alkali 106 Once the LAE is clarified the cleaned water is exited via a cleaned water port and associated conduit 108 to an existing wash water tank 109. The wash water tank 109 is connected via a port and associated conduit 110 to the yard 101 for re-use washing the yard.

Sludge is removed from the tank 109 via a port and associated conduit 111.

DETAILED DISCUSSION OF THE INVENTION INCLUDING ALTERNATE WAYS TO IMPLEMENT THE INVENTION The present invention has application to cattle. In particular, but not limited to, dairy cows.

However, it should be appreciated, that the present invention can also be used in relation to other agricultural animals, which are grouped in areas where liquid effluent is going to be collected, and needs to be disposed of.

The coagulant may be selected from, but should not be limited to: • ferric sulphate; • ferric chloride; • aluminium sulphate; • polyaluminium chloride; James & Wells ref: 303389/14 JV • polyaluminium sulphate; • polyferric sulphate; • sodium aluminate; and • polyiron chloride.

Other coagulants are envisaged. For example, Aluminium sulphate or some synthetic or natural organic polymers. However, whether such coagulants are used in practice may be influenced by their effectiveness, cost, and/or any perceived food contamination or health risks.

The amount of coagulant that is added to the liquid animal effluent will depend on: - the type of animal effluent; and - the turbidity of the effluent.

For example, the inventors have found for dairy effluent: if the turbidity is around 1000NTU then the coagulant may be added at a rate of 100 – 150 mg Fe per litre of effluent; or, if the turbidity of the liquid animal effluent is around 2500NTU then the coagulant may be added at a rate of 250 – 550 mg Fe/ per litre of effluent.

The pre-determined value of the turbidity may depend on the end use to which the “cleaned water” obtained from the LAE is to be put.

For on farm applications in New Zealand the pre-determined value may be around 25NTU.

The source of liquid animal effluent (LAE) may generally be a cattle yard, or a milking platform for dairy cows.

However, the source of LAE should not be limited and may include one or more of the following: - stock lanes (or stock races); - stock feed pads; - cattle trucks; - sheep trucks; - effluent disposal tanks (for sheep/cattle trucks); and - animal holding pens or yards.

James & Wells ref: 303389/14 JV Preferably, the source of alkalinity (alkali) may include but not limited to e.g. sodium hypochlorite, calcium hydroxide, calcium oxide, hydrated lime, sodium hydroxide, sodium aluminate, soda ash, and lime.

Preferably, the coagulant-aid/flocculant-aid may be hydrated lime or fine agricultural lime (i.e. calcium hydroxide particles). However, this should not be seen as limiting as the coagulant-aid may include e.g. calcium oxide, bentonite, clay, kaolinite, sodium silicate, calcium carbonate, powdered activated carbon, fine sand, organic polymers and activated silica.

In general the source(s) of coagulant, alkali, disinfectant and coagulant aid may be containers or other receptacles in fluid communication with the treatment tank.

Preferably, the disinfectant may be sodium hypochlorite.

However, other disinfectants may include but should not be limited to: • chlorine; • Ozone; • chlorine dioxide; • UV light; and • hypocholorus acid.

The cleaned water outlet may come in a variety of different forms without departing from the scope of the present invention which may include: • an outlet port in the tank itself; • a conduit which has direct access to the LAE within the tank where the tank has an open top; and • such an outlet may then remove cleaned water from the tank following treatment.

However, this list should not be seen as limiting. In most embodiments one or more conduits or conduit networks may be associated with the outlet.

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

James & Wells ref: 303389/14 JV Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

James & Wells ref: 303389/14 JV

Claims (4)

WHAT WE CLAIM IS:

1. A single tank liquid animal effluent treatment system comprising: - a source of liquid animal effluent (LAE); - a treatment tank connected to said source of LAE which captures said LAE; - a sludge removal outlet on said treatment tank connected to a sludge containment receptacle; - a source of a coagulant connected to said treatment tank; - an (optional) source of alkalinity connected to said treatment tank; - an (optional) source of a disinfectant connected to said treatment tank; - a (optional) source of coagulant/flocculant aid connected to said treatment tank; - a delivery mechanism associated with each of the sources of coagulant, coagulant aid; alkalinity and disinfectant; - a turbidity sensor for measuring turbidity and relaying information to a controller which is associated with the coagulant delivery system; - a pH sensor for measuring pH and relaying information to a controller which is associated with the coagulant and alkali delivery system; - a cleaned water outlet on said treatment tank which is connected to one or more on- farm water systems able to utilise cleaned water.

2. A single tank liquid effluent treatment system as claimed in claim 1 wherein the source of alkalinity and source of disinfectant is one and the same.

3. A single tank liquid effluent treatment system as claimed in claim 2 wherein sodium hypochlorite is both the disinfectant and the alkali.

4. A single tank liquid animal effluent treatment system as claimed in claim 1 wherein the source of coagulant is provided by ferric chloride or ferric sulphate or polyferric sulphate and (optionally) a source of alkalinity is provided by hydrated lime and/or sodium hypochlorite.